1.
Checker shadow illusion
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The checker shadow illusion is an optical illusion published by Edward H. Adelson, Professor of Vision Science at MIT in 1995. The image depicts a checkerboard with light and dark squares, partly shadowed by another object, the optical illusion is that the area labeled A appears to be a darker color than the area labeled B. That the two squares are the color can be proven using the following methods, Open the illusion in an image editing program. By viewing patches of the squares without the context, you can remove the effect of the illusion. A piece of cardboard with two circles removed will work as a mask for a screen or for a printed piece of paper. Connect the squares with a rectangle of the color, as seen in the figure to the right. Print the image and cut out the squares, cut out each square along the edges. Without the surrounding context, the effect of the illusion is dispelled. This can be done by using the tool in image editing programs, such as Gimp to sample the values of A & B. Simply cropping a portion of Edward Adelsons original shows that most of the board, as can be seen in the picture on the left the illusion remains very strong even with only a small portion of the board remaining. The visual system is still persuaded to see a 3D object in which A and B have differing original shades, a further modification is to add an extra polygon between A and B with smaller size but similar shade. This produces a flip-flop illusion effect similar to the Rabbit–duck illusion and My Wife and My Mother-in-Law illusions. When gazing at the picture on the right the system sees either a checkerboard - with A different from B. In this case the problem is to determine the shade of the checks on the floor. Just measuring the light coming from a surface is not enough, the visual system uses several tricks to determine where the shadows are and how to compensate for them, in order to determine the shade of gray paint that belongs to the surface. The first trick is based on local contrast, in shadow or not, a check that is lighter than its neighboring checks is probably lighter than average, and vice versa. In the figure, the check in shadow is surrounded by darker checks. Thus, even though the check is physically dark, it is light compared to its neighbors
2.
Luminance
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Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light passes through, is emitted or reflected from a particular area. The SI unit for luminance is candela per square metre, a non-SI term for the same unit is the nit. The CGS unit of luminance is the stilb, which is equal to one candela per square centimetre or 10 kcd/m2, luminance is often used to characterize emission or reflection from flat, diffuse surfaces. The luminance indicates how much power will be detected by an eye looking at the surface from a particular angle of view. Luminance is thus an indicator of how bright the surface will appear, in this case, the solid angle of interest is the solid angle subtended by the eyes pupil. Luminance is used in the industry to characterize the brightness of displays. A typical computer display emits between 50 and 300 cd/m2, the sun has luminance of about 1. 6×109 cd/m2 at noon. Luminance is invariant in geometric optics and this means that for an ideal optical system, the luminance at the output is the same as the input luminance. For real, passive, optical systems, the luminance is at most equal to the input. As an example, if one uses a lens to form an image that is smaller than the source object, the luminous power is concentrated into a smaller area, meaning that the illuminance is higher at the image. The light at the plane, however, fills a larger solid angle so the luminance comes out to be the same assuming there is no loss at the lens. The image can never be brighter than the source, if light travels through a lossless medium, the luminance does not change along a given light ray. In the case of a perfectly diffuse reflector, the luminance is isotropic, then the relationship is simply L v = E v R / π A variety of units have been used for luminance, besides the candela per square metre. One candela per square metre is equal to, 10−4 stilbs π apostilbs π×10−4 lamberts 0.292 foot-lamberts Retinal damage can occur when the eye is exposed to high luminance, damage can occur due to local heating of the retina. Photochemical effects can cause damage, especially at short wavelengths. Also available in PDF form and Google Docs online version Autodesk Design Academy Measuring Light Levels
3.
Mach bands
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Mach bands is an optical illusion named after the physicist Ernst Mach. It exaggerates the contrast between edges of the slightly differing shades of gray, as soon as they one another. The Mach bands effect is due to the spatial high-boost filtering performed by the visual system on the luminance channel of the image captured by the retina. This filtering is largely performed in the retina itself, by lateral inhibition among its neurons, the effect is independent of the orientation of the boundary. A false-positive radiological diagnosis of dental caries can easily arise if the practitioner does not take account the likelihood of this illusion. Mach bands manifest adjacent to metal restorations or appliances and the boundary between enamel and dentin, Mach bands may also result in the misdiagnosis of horizontal root fractures because of the differing radiographic intensities of tooth and bone. Mach effect can lead to an erroneous diagnosis of pneumothorax by creating a dark line at the lung periphery. Proceedings of the National Academy of Sciences, eagleman, DM Visual Illusions and Neurobiology. Demonstration of the Mach band Laboratory of Dale Purves, MD
4.
Contrast (vision)
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Contrast is the difference in luminance or colour that makes an object distinguishable. In visual perception of the world, contrast is determined by the difference in the color and brightness of the object. The human visual system is sensitive to contrast than absolute luminance. The maximum contrast of an image is the contrast ratio or dynamic range, the human contrast sensitivity function shows a typical band-pass filter shape peaking at around 4 cycles per degree with sensitivity dropping off either side of the peak. The high-frequency cut-off represents the optical limitations of the systems ability to resolve detail and is typically about 60 cycles per degree. The high-frequency cut-off is related to the density of the retinal photoreceptor cells. The low frequency drop-off is due to lateral inhibition within the ganglion cells. A typical retinal ganglion cell presents a centre region with either excitation or inhibition, one experimental phenomenon is the inhibition of blue in the periphery if blue light is displayed against white, leading to a yellow surrounding. The yellow is derived from the inhibition of blue on the surroundings by the center, since white minus blue is red and green, this mixes to become yellow. For example, in the case of computer displays, contrast depends on the properties of the picture source or file. For some screens the angle between the surface and the observers line of sight is also important. There are many definitions of contrast. Some include color, others do not, travnikova laments, Such a multiplicity of notions of contrast is extremely inconvenient. It complicates the solution of many applied problems and makes it difficult to compare the results published by different authors, various definitions of contrast are used in different situations. Here, luminance contrast is used as an example, but the formulas can also be applied to other physical quantities, in many cases, the definitions of contrast represent a ratio of the type Luminance difference Average luminance. The rationale behind this is that a difference is negligible if the average luminance is high. Below, some definitions are given. Weber contrast is defined as I − I b I b, with I and I b representing the luminance of the features, the measure is also referred to as Weber fraction, since it is the term that is constant in Webers Law
5.
Illusion
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An illusion is a distortion of the senses, revealing how the brain normally organizes and interprets sensory stimulation. Though illusions distort reality, they are shared by most people. Illusions may occur with any of the senses, but visual illusions are the best-known. The emphasis on visual illusions occurs because vision often dominates the other senses, for example, individuals watching a ventriloquist will perceive the voice is coming from the dummy since they are able to see the dummy mouth the words. Some illusions are based on general assumptions the brain makes during perception and these assumptions are made using organizational principles, an individuals capacity for depth perception and motion perception, and perceptual constancy. Other illusions occur because of biological sensory structures within the body or conditions outside of the body within one’s physical environment. The term illusion refers to a form of sensory distortion. Unlike a hallucination, which is a distortion in the absence of a stimulus, for example, hearing voices regardless of the environment would be a hallucination, whereas hearing voices in the sound of running water would be an illusion. Mimes are known for a repertoire of illusions that are created by physical means, the mime artist creates an illusion of acting upon or being acted upon by an unseen object. These illusions exploit the audiences assumptions about the physical world, well-known examples include walls, climbing stairs, leaning, descending ladders, and pulling and pushing. An optical illusion is characterized by visually perceived images that are deceptive or misleading, therefore, the information gathered by the eye is processed by the brain to give, on the face of it, a percept that does not tally with a physical measurement of the stimulus source. The human brain constructs a world inside our head based on what it samples from the surrounding environment, however, sometimes it tries to organise this information it thinks best while other times it fills in the gaps. This way in which our brain works is the basis of an illusion, an auditory illusion is an illusion of hearing, the sound equivalent of an optical illusion, the listener hears either sounds which are not present in the stimulus, or impossible sounds. In short, audio illusions highlight areas where the ear and brain, as organic, makeshift tools. One example of an illusion is a Shepard tone. Interestingly, the areas activated during illusory tactile perception are similar to those activated during actual tactile stimulation. Tactile illusions can also be elicited through haptic technology and these illusory tactile objects can be used to create virtual objects. A temporal illusion is a distortion in the perception of time, in such cases, a person may momentarily perceive time as slowing down, stopping, speeding up, or running backwards
6.
Visual system
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The visual system is the part of the central nervous system which gives organisms the ability to process visual detail, as well as enabling the formation of several non-image photo response functions. It detects and interprets information from visible light to build a representation of the surrounding environment, the psychological process of visual information is known as visual perception, a lack of which is called blindness. Non-image forming visual functions, independent of perception, include the pupillary light reflex. This article mostly describes the system of mammals, humans in particular. Together the cornea and lens refract light into a small image, the retina transcribes this image into electrical pulses using rods and cones. The optic nerve then carries these pulses through the optic canal, upon reaching the optic chiasm the nerve fibers decussate. The fibers then branch and terminate in three places, most end in the lateral geniculate nucleus. Before the LGN forwards the pulses to V1 of the visual cortex it gauges the range of objects, the LGN also sends some fibers to V2 and V3. V1 performs edge-detection to understand spatial organization, V2 both forwards pulses to V1 and receives them. Pulvinar is responsible for saccade and visual attention, V2 serves much the same function as V1, however, it also handles illusory contours, determining depth by comparing left and right pulses, and foreground distinguishment. V3 helps process ‘global motion’ of objects, V3 connects to V1, V2, and the inferior temporal cortex. V4 recognizes simple shapes, gets input from V1, V2, V3, LGN, v5’s outputs include V4 and its surrounding area, and eye-movement motor cortices. V5’s functionality is similar to that of the other V’s, however, V6 works in conjunction with V5 on motion analysis. V5 analyzes self-motion, whereas V6 analyzes motion of objects relative to the background, v6’s primary input is V1, with V5 additions. V6 houses the topographical map for vision, V6 outputs to the region directly around it. V6A has direct connections to arm-moving cortices, including the premotor cortex, the inferior temporal gyrus recognizes complex shapes, objects, and faces or, in conjunction with the hippocampus, creates new memories. The pretectal area is seven unique nuclei, anterior, posterior and medial pretectal nuclei inhibit pain, aid in REM, and aid the accommodation reflex, respectively. The Edinger-Westphal nucleus moderates pupil dilation and aids in convergence of the eyes, nuclei of the optic tract are involved in smooth pursuit eye movement and the accommodation reflex, as well as REM
7.
Perception
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Perception is the organization, identification, and interpretation of sensory information in order to represent and understand the environment. All perception involves signals in the system, which in turn result from physical or chemical stimulation of the sense organs. For example, vision involves light striking the retina of the eye, smell is mediated by odor molecules, Perception is not the passive receipt of these signals, but is shaped by learning, memory, expectation, and attention. Perception can be split into two processes, firstly, processing sensory input, which transforms these low-level information to higher-level information. Secondly, processing which is connected with a persons concepts and expectations, Perception depends on complex functions of the nervous system, but subjectively seems mostly effortless because this processing happens outside conscious awareness. Since the rise of psychology in the 19th Century, psychologys understanding of perception has progressed by combining a variety of techniques. Psychophysics quantitatively describes the relationships between the qualities of the sensory input and perception. Sensory neuroscience studies the mechanisms underlying perception. Perceptual systems can also be studied computationally, in terms of the information they process, Perceptual issues in philosophy include the extent to which sensory qualities such as sound, smell or color exist in objective reality rather than in the mind of the perceiver. The perceptual systems of the brain enable individuals to see the world around them as stable, even though the information is typically incomplete. Human and animal brains are structured in a way, with different areas processing different kinds of sensory information. Some of these take the form of sensory maps, mapping some aspect of the world across part of the brains surface. These different modules are interconnected and influence each other, for instance, taste is strongly influenced by smell. The process of perception begins with an object in the real world, by means of light, sound or another physical process, the object stimulates the bodys sensory organs. These sensory organs transform the energy into neural activity—a process called transduction. This raw pattern of activity is called the proximal stimulus. These neural signals are transmitted to the brain and processed, the resulting mental re-creation of the distal stimulus is the percept. An example would be a shoe, the shoe itself is the distal stimulus
8.
Reality
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Reality is the state of things as they actually exist, rather than as they may appear or might be imagined. Reality includes everything that is and has been, whether or not it is observable or comprehensible, a still broader definition includes that which has existed, exists, or will exist. By contrast existence is restricted solely to that which has physical existence or has a direct basis in it in the way that thoughts do in the brain. Reality is often contrasted with what is imaginary, illusory, delusional, in the mind, dreams, what is false, what is fictional, at the same time, what is abstract plays a role both in everyday life and in academic research. For instance, causality, virtue, life, and distributive justice are abstract concepts that can be difficult to define, but they are only rarely equated with pure delusions. Both the existence and reality of abstractions are in dispute, one extreme position regards them as mere words and this disagreement is the basis of the philosophical problem of universals. The truth refers to what is real, while falsity refers to what is not, a common colloquial usage would have reality mean perceptions, beliefs, and attitudes toward reality, as in My reality is not your reality. This is often used just as a colloquialism indicating that the parties to a conversation agree, or should agree, for example, in a religious discussion between friends, one might say, You might disagree, but in my reality, everyone goes to heaven. Reality can be defined in a way that links it to world views or parts of them, Reality is the totality of all things, structures, events and phenomena and it is what a world view ultimately attempts to describe or map. Certain ideas from physics, philosophy, sociology, literary criticism, one such belief is that there simply and literally is no reality beyond the perceptions or beliefs we each have about reality. Many of the concepts of science and philosophy are often defined culturally and socially and this idea was elaborated by Thomas Kuhn in his book The Structure of Scientific Revolutions. The Social Construction of Reality, a book about the sociology of knowledge written by Peter L. Berger and it explained how knowledge is acquired and used for the comprehension of reality. Out of all the realities, the reality of life is the most important one since our consciousness requires us to be completely aware. Philosophy addresses two different aspects of the topic of reality, the nature of reality itself, and the relationship between the mind and reality. On the one hand, ontology is the study of being, and the topic of the field is couched, variously, in terms of being, existence, what is. The task in ontology is to describe the most general categories of reality, if a philosopher wanted to proffer a positive definition of the concept reality, it would be done under this heading. As explained above, some philosophers draw a distinction between reality and existence, in fact, many analytic philosophers today tend to avoid the term real and reality in discussing ontological issues. But for those who would treat is real the same way they treat exists and it has been widely held by analytic philosophers that it is not a property at all, though this view has lost some ground in recent decades
9.
Richard Gregory
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Richard Langton Gregory CBE FRS FRSE was a British psychologist and Emeritus Professor of Neuropsychology at the University of Bristol. Richard Gregory was born in London, the son of Christopher Clive Langton Gregory and his father was an astronomer and the first Director of the University of London Observatory. Gregory served with the Royal Air Forces Signals branch during World War II, one of Sir Frederic Bartletts last pupils at Cambridge, Gregory admitted to having been inspired by him. He was made an Honorary Fellow of Downing in 1999 and he was Head of the Bionics Research Laboratory, Professor of Bionics, and Department chairman 1968–70. Gregory was founding editor of the journal Perception, which emphasized phenomenology and he was a founding member of the Experimental Psychology Society and served as its President in 1981-2. He collaborated with W. E. Hick for the influential paper On the rate of gain of information. I was the subject for his gain of information experiment to complete the course, as he was the only other subject. In 1978, he founded The Exploratory, a science centre in Bristol. In 1989, he was appointed Osher Visiting Fellow of the Exploratorium, Gregory suggested Hermann von Helmholtz as his hero from past psychology, describing him as. The modern founder of the science of perception and he appeared on, or was an advisor to, numerous science-related television programmes in the UK and worldwide. His particular interest was in optical illusions and what these revealed about human perception and he wrote and edited several books, notably Eye and Brain and Mind in Science. One of his hobbies was punning, in April 1993 he was the guest for BBC Radio 4s Desert Island Discs, where his favourite choice was Beethovens Piano Sonata No.30. Having suffered a stroke a few days earlier, he died on 17 May 2010 at the Bristol Royal Infirmary, surrounded by family, in 1967 he delivered the Royal Institution Christmas Lectures on The Intelligent Eye. Between them, the two Germans laid the basis of investigating how the work, especially sight and hearing. According to Gregory, Helmholtz should take the credit for realising that perception is not just an acceptance of stimuli. Gregory progressed this idea with a key analogy, although this takes place on a quite different time-scale, and inside one head instead of a community, nevertheless, according to Gregory, perception shares many traits with scientific method. A series of works by Gregory developed this idea in some detail, gregorys ideas ran counter to those of the American direct realist psychologist J. J. Gibson, whose 1950 The Perception of the Visual World was dominant when Gregory was a younger man, Gregory argued that optical illusions, such as the illusory contours in the Kanizsa triangle, demonstrated the Bayesian processing of perceptual information by the brain
10.
Afterimage
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Afterimage is a non-specific term that refers to an image continuing to appear in ones vision after the exposure to the original image has ceased. An afterimage may be a phenomenon or may be pathological. Illusory palinopsia may be an exaggeration of physiological afterimages. After images occur because photochemical activity in the retina continues even when you are no longer experiencing the original stimulus, the remainder of this article refers to physiological afterimages. A common physiological afterimage is the dim area that seems to float before ones eyes after briefly looking into a light source, Afterimages are a common symptom of visual snow. Negative afterimages are caused when the eyes photoreceptors, primarily known as rods and cones, adapt to overstimulation, newer evidence suggests there is cortical contribution as well. Normally, the image is moved to a fresh area of the retina with small eye movements known as microsaccades. However, if the image is large or the eye remains too steady, the photoreceptors that are constantly exposed to the same stimulus will eventually exhaust their supply of photopigment, resulting in a decrease in signal to the brain. This phenomenon can be seen moving from a bright environment to a dim one. These effects are accompanied by neural adaptations in the lobe of the brain that function similar to color balance adjustments in photography. These adaptations attempt to keep vision consistent in dynamic lighting, when all wavelengths stimulate the retinal region adapted to green light, the M and L cones contribute less to the resulting percept because their photopigments absorb less light than the S cones. Afterimages are the complementary hue of the stimulus and trichromatic theory fails to account for this fact. Ewald Hering explained how the brain sees afterimages, in terms of three pairs of primary colors and this opponent process theory states that the human visual system interprets color information by processing signals from cones and rods in an antagonistic manner. The opponent color theory suggests that there are three opponent channels, red versus green, blue versus yellow, and black versus white, responses to one color of an opponent channel are antagonistic to those to the other color. Therefore, an image will produce a magenta afterimage. The green color fatigues the green photoreceptors, so produce a weaker signal. Anything resulting in green, is interpreted as its paired primary color. Example movie which produces distortion illusion after one watches it and looks away, positive afterimages, by contrast, appear the same color as the original image
11.
Cognition
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Cognition is the mental action or process of acquiring knowledge and understanding through thought, experience, and the senses. Human cognition is conscious and unconscious, concrete or abstract, as well as intuitive, cognitive processes use existing knowledge and generate new knowledge. These and other different approaches to the analysis of cognition are synthesised in the field of cognitive science. Within psychology and philosophy, the concept of cognition is closely related to concepts such as mind. It encompasses the functions, mental processes, and states of intelligent entities. It is also used in a branch of psychology called social cognition to explain attitudes, attribution. In cognitive psychology and cognitive engineering, cognition is typically assumed to be processing in a participant’s or operator’s mind or brain. Cognition can in specific and abstract sense also be artificial. The term cognition is often used to mean cognitive abilities or cognitive skills. The word cognition comes from the Latin verb cognosco meaning to conceptualize or to recognize, Cognition is a word that dates back to the 15th century, when it meant thinking and awareness. Attention to the process came about more than eighteen centuries ago, beginning with Aristotle and his interest in the inner workings of the mind. Aristotle focused on cognitive areas pertaining to memory, perception, wilhelm Wundt heavily emphasized the notion of what he called introspection, examining the inner feelings of an individual. With introspection, the subject had to be careful to describe his or her feelings in the most objective manner possible in order for Wundt to find the information scientific, Hermann Ebbinghaus conducted cognitive studies that mainly examined the function and capacity of human memory. Ebbinghaus developed his own experiment in which he constructed over 2,000 syllables made out of nonexistent words and he then examined his own personal ability to learn these non-words. He purposely chose non-words as opposed to words to control for the influence of pre-existing experience on what the words might symbolize. Ebbinghaus observed and hypothesized a number of variables that may have affected his ability to learn, one of the reasons, he concluded, was the amount of time between the presentation of the list of stimuli and the recitation or recall of same. Ebbinghaus was the first to record and plot a curve. His work heavily influenced the study of serial position and its effect on memory, mary Whiton Calkins was an influential American pioneer in the realm of psychology
12.
Unconscious inference
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It has since received new attention from modern research, and the work of recent scholars, notably that of James Uleman, has approached Helmholtzs view. In the third and final volume of his Handbuch der physiologischen Optik, while optical illusions are the most obvious instances of unconscious inference, peoples perceptions of each other are similarly influenced by such unintended, unconscious conclusions. We consider him as being angry or in pain according as he shows us one or the mode of countenance. He arouses fright or sympathy in us, and the conviction that all this is only show and play does not hinder our emotions at all. On the contrary, a tale of this sort, which we seem to enter into ourselves, grips. The mere sight of another person is sufficient to produce an emotional attitude without any basis whatsoever. So whatever impressions this unconscious inference process leads to, they strike our consciousness as a foreign, the reason, Helmholtz suggested, lies in the way visual sensory impressions are processed neurologically. The higher cortical centres responsible for conscious deliberation are not involved in the formation of visual impressions, however, as the process is spontaneous and automatic, we are unable to account for just how we arrived at our judgments. In recognizing these attitude-formation mechanisms underlying the human processing of nonverbal cues, as Daniel Gilbert has pointed out, Helmholtz presaged many current thinkers not only by postulating the existence of such operations, but also by describing their general features. At the same time, he added, it is fair to say that Helmholtzs ideas about the social inference process have exerted no impact whatsoever on social psychology. Indeed, psychologists have largely felt that Helmholtz had fallen prey to an error in reasoning, as Edwin G. Boring summed up the debate, Since an inference is ostensibly a conscious process and can therefore be neither unconscious nor immediate, view was rejected as self-contradictory. Boring, Edwin G. Sensation and Perception in the History of Experimental Psychology, prejudice and inferential communication, a new look at an old problem. In Eibl-Eibesfeldt, Irenäus, Salter, Frank Kemp, der Einfluß nonverbaler Kommunikation auf Kultur und Politik. Thinking lightly about others, Automatic components of the inference process. In Uleman, J. S. Bargh, J. A, quotations are from the English translation produced by Optical Society of America, Treatise on Physiological Optics. The beginnings of the philosophy of music in England. Francis Norths A philosophical essay of musick with comments of Isaac Newton, Roger North, newman, L. S. Moskowitz, G. B. Uleman, J. S. Zanna, M. P. ed, people as flexible interpreters, Evidence and issues from spontaneous trait inference, Advances in Experimental Social Psychology, San Diego, CA, Academic Press,28, 211–279
13.
Optical illusion
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An optical illusion is an illusion caused by the visual system and characterized by visually perceived images that differ from objective reality. The information gathered by the eye is processed in the brain to give a percept that does not tally with a measurement of the stimulus source. Pathological visual illusions arise from a pathological exaggeration in physiological visual perception mechanisms causing the aforementioned types of illusions, optical illusions are often classified into categories including the physical and the cognitive or perceptual, and contrasted with optical hallucinations. The Hermann grid illusion and Mach bands are two illusions that are best explained using a biological approach, once a receptor is active, it inhibits adjacent receptors. This inhibition creates contrast, highlighting edges, in the Hermann grid illusion the gray spots appear at the intersection because of the inhibitory response which occurs as a result of the increased dark surround. Lateral inhibition has also used to explain the Hermann grid illusion. More recent empirical approaches to optical illusions have had success in explaining optical phenomena with which theories based on lateral inhibition have struggled. A pathological visual illusion is a distortion of an external stimulus and are often diffuse. Pathological visual illusions usually occur throughout the field, suggesting global excitability or sensitivity alterations. Alternatively visual hallucination is the perception of a visual stimulus where none exists. Visual hallucinations are often from focal dysfunction and are usually transient and these symptoms may indicate an underlying disease state and necessitate seeing a medical practitioner. Etiologies associated with visual illusions include multiple types of ocular disease, migraines, hallucinogen persisting perception disorder, head trauma. If the visual illusions are diffuse and persistent, they affect the patients quality of life. These symptoms are refractory to treatment and may be caused by any of the aforementioned etiologes. There is no treatment for these visual disturbances. Cognitive illusions are commonly divided into ambiguous illusions, distorting illusions, paradox illusions, ambiguous illusions are pictures or objects that elicit a perceptual switch between the alternative interpretations. The Necker cube is an example, another instance is the Rubin vase. Distorting or geometrical-optical illusions are characterized by distortions of size, length, a striking example is the Café wall illusion
14.
Visual perception
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Visual perception is the ability to interpret the surrounding environment using light in the visible spectrum reflected by the objects in the environment. The resulting perception is known as visual perception, eyesight, sight. The visual system in animals allows individuals to assimilate information from their surroundings, the act of seeing starts when the cornea and then the lens of the eye focuses light from its surroundings onto a light-sensitive membrane in the back of the eye, called the retina. The retina is actually part of the brain that is isolated to serve as a transducer for the conversion of light into neuronal signals. These signals are processed via complex feedforward and feedback processes by different parts of the brain, signals from the retina can also travel directly from the retina to the superior colliculus. The perception of objects and the totality of the scene is accomplished by the visual association cortex. The visual association cortex combines all sensory information perceived by the cortex which contains thousands of modules that are part of modular neural networks. The neurons in the cortex send axons to the extrastriate cortex. The major problem in perception is that what people see is not simply a translation of retinal stimuli. Thus people interested in perception have long struggled to explain what visual processing does to create what is actually seen, there were two major ancient Greek schools, providing a primitive explanation of how vision is carried out in the body. The first was the theory which maintained that vision occurs when rays emanate from the eyes and are intercepted by visual objects. If an object was seen directly it was by means of coming out of the eyes. This theory was championed by scholars like Euclid and Ptolemy and their followers, the second school advocated the so-called intro-mission approach which sees vision as coming from something entering the eyes representative of the object. Plato makes this assertion in his dialogue Timaeus, as does Aristotle, alhazen carried out many investigations and experiments on visual perception, extended the work of Ptolemy on binocular vision, and commented on the anatomical works of Galen. Leonardo da Vinci is believed to be the first to recognize the special qualities of the eye. He wrote The function of the human eye, was described by a large number of authors in a certain way. But I found it to be completely different and his main experimental finding was that there is only a distinct and clear vision at the line of sight—the optical line that ends at the fovea. Although he did not use these words literally he actually is the father of the distinction between foveal and peripheral vision
15.
Foehn wind
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A föhn or foehn is a type of dry, warm, down-slope wind that occurs in the lee of a mountain range. It is a rain shadow wind that results from the subsequent adiabatic warming of air that has dropped most of its moisture on windward slopes. As a consequence of the different adiabatic rates of moist and dry air. Föhn winds can raise temperatures by as much as 14 °C in just a matter of minutes, Central Europe enjoys a warmer climate due to the Föhn, as moist winds off the Mediterranean Sea blow over the Alps. In German-speaking countries, where popular superstition attributes all kinds of illnesses to various movements of air, there is no scientific proof of such a link. Winds of this type are also called snow-eaters for their ability to make snow melt or sublimate rapidly, Föhn winds are notorious among mountaineers in the Alps, especially those climbing the Eiger, for whom the winds add further difficulty in ascending an already difficult peak. They are also associated with the spread of wildfires, making some regions which experience these winds particularly fire-prone. Anecdotally, residents in areas of frequent föhn winds report a variety of illnesses ranging from migraines to psychosis, the first clinical review of these effects was published by the Austrian physician Anton Czermak in the 19th century. A study by the Ludwig-Maximilians-Universität München found that suicide and accidents increased by 10 percent during föhn winds in Central Europe, the causation of Föhnkrankheit is yet unproven. Labeling for preparations of aspirin combined with caffeine, codeine and the like will sometimes include Föhnkrankheit amongst the indications, evidence for effects from Chinook winds remain anecdotal. The condition exists because warm moist air rises through orographic lifting up, because atmospheric pressure decreases as altitude increases, the air expands and cools adiabatically at the dry adiabatic lapse rate to the point that the air reaches its dew point. Dew point is the temperature at which condensation begins at a given pressure, condensation is also commonly followed by precipitation on the top and windward sides of the mountain. As the air descends on the side, it is warmed by adiabatic compression at the dry adiabatic lapse rate. Because the air has lost much of its water vapor content. The name Foehn arose in the Alpine region, in the Southern Alps, the phenomenon is known as föhn but also Italian, favonio and Slovene, fen. The German word Fön, a trademark, also means hairdryer. Regionally, these winds are known by different names. Often associated with orographic lifting on the windward side of the escarpment Föhn in Ostrobothnia and Western Lapland in Finland as moist air crosses Scandinavian Mountains
16.
Depth perception
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Depth perception is the visual ability to perceive the world in three dimensions and the distance of an object. Depth perception arises from a variety of depth cues, Binocular cues include stereopsis, eye convergence, disparity, and yielding depth from binocular vision through exploitation of parallax. Monocular cues include size, distant objects subtend smaller visual angles than near objects, grain, size, Monocular cues provide depth information when viewing a scene with one eye. Motion parallax When an observer moves, the apparent relative motion of several stationary objects against a background gives hints about their relative distance, If information about the direction and velocity of movement is known, motion parallax can provide absolute depth information. This effect can be seen clearly when driving in a car, nearby things pass quickly, while far off objects appear stationary. Some animals that lack binocular vision due to their eyes having little common field-of-view employ motion parallax more explicitly than humans for depth cueing. Depth from motion When an object moves toward the observer, the projection of an object expands over a period of time. Another name for this phenomenon is depth from optical expansion, the dynamic stimulus change enables the observer not only to see the object as moving, but to perceive the distance of the moving object. Thus, in context, the changing size serves as a distance cue. However, calculation of TTC is, strictly speaking, perception of velocity rather than depth, but if the cube rotates, the visual system will extract the necessary information for perception of the third dimension from the movements of the lines, and a cube is seen. This is an example of the depth effect. Perspective The property of parallel lines converging in the distance, at infinity, an example would be standing on a straight road, looking down the road, and noticing the road narrows as it goes off in the distance. Relative size If two objects are known to be the size but their absolute size is unknown, relative size cues can provide information about the relative depth of the two objects. If one subtends a visual angle on the retina than the other. For example, people are familiar with the size of an average automobile. This prior knowledge can be combined with information about the angle it subtends on the retina to determine the depth of an automobile in a scene. Due to this, images seem hazy the farther they are away from a point of view. In computer graphics, this is called distance fog
17.
Ptolemy
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Claudius Ptolemy was a Greek writer, known as a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in the city of Alexandria in the Roman province of Egypt, wrote in Koine Greek, beyond that, few reliable details of his life are known. His birthplace has been given as Ptolemais Hermiou in the Thebaid in a statement by the 14th-century astronomer Theodore Meliteniotes. This is a very late attestation, however, and there is no reason to suppose that he ever lived elsewhere than Alexandria. Ptolemy wrote several treatises, three of which were of importance to later Byzantine, Islamic and European science. The first is the astronomical treatise now known as the Almagest, although it was entitled the Mathematical Treatise. The second is the Geography, which is a discussion of the geographic knowledge of the Greco-Roman world. The third is the treatise in which he attempted to adapt horoscopic astrology to the Aristotelian natural philosophy of his day. This is sometimes known as the Apotelesmatika but more known as the Tetrabiblos from the Greek meaning Four Books or by the Latin Quadripartitum. The name Claudius is a Roman nomen, the fact that Ptolemy bore it indicates he lived under the Roman rule of Egypt with the privileges and political rights of Roman citizenship. It would have suited custom if the first of Ptolemys family to become a citizen took the nomen from a Roman called Claudius who was responsible for granting citizenship, if, as was common, this was the emperor, citizenship would have been granted between AD41 and 68. The astronomer would also have had a praenomen, which remains unknown and it occurs once in Greek mythology, and is of Homeric form. All the kings after him, until Egypt became a Roman province in 30 BC, were also Ptolemies, abu Mashar recorded a belief that a different member of this royal line composed the book on astrology and attributed it to Ptolemy. The correct answer is not known”, Ptolemy wrote in Greek and can be shown to have utilized Babylonian astronomical data. He was a Roman citizen, but most scholars conclude that Ptolemy was ethnically Greek and he was often known in later Arabic sources as the Upper Egyptian, suggesting he may have had origins in southern Egypt. Later Arabic astronomers, geographers and physicists referred to him by his name in Arabic, Ptolemys Almagest is the only surviving comprehensive ancient treatise on astronomy. Ptolemy presented his models in convenient tables, which could be used to compute the future or past position of the planets. The Almagest also contains a catalogue, which is a version of a catalogue created by Hipparchus
18.
Physiology
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Physiology is the scientific study of normal mechanisms, and their interactions, which operate within a living system. A sub-discipline of biology, its focus is in how organisms, organ systems, organs, cells, and biomolecules carry out the chemical or physical functions that exist in a living system. Given the size of the field, it is divided into, among others, animal physiology, plant physiology, cellular physiology, microbial physiology, bacterial physiology, and viral physiology. The Nobel Prize in Physiology or Medicine is awarded to those who make significant achievements in this discipline by the Royal Swedish Academy of Sciences. In medicine, a state is one occurring from normal body function, rather than pathologically. Physiological studies date back to the ancient civilizations of India and Egypt alongside anatomical studies, the study of human physiology as a medical field dates back to at least 420 BC to the time of Hippocrates, also known as the father of medicine. Hippocrates incorporated his belief called the theory of humours, which consisted of four basic substance, earth, water, air. Each substance is known for having a corresponding humour, black bile, phlegm, blood and yellow bile, Hippocrates also noted some emotional connections to the four humours, which Claudis Galenus would later expand on. The critical thinking of Aristotle and his emphasis on the relationship between structure and function marked the beginning of physiology in Ancient Greece. Like Hippocrates, Aristotle took to the theory of disease. Claudius Galenus, known as Galen of Pergamum, was the first to use experiments to probe the functions of the body, unlike Hippocrates though, Galen argued that humoral imbalances can be located in specific organs, including the entire body. His modification of this theory better equipped doctors to more precise diagnoses. Galen was also the founder of experimental physiology, and for the next 1,400 years, Galenic physiology was a powerful and influential tool in medicine. Jean Fernel, a French physician, introduced the term physiology, inspired in the work of Adam Smith, Milne-Edwards wrote that the body of all living beings, whether animal or plant, resembles a factory. Where the organs, comparable to workers, work incessantly to produce the phenomena that constitute the life of the individual, in more differentiated organisms, the functional labor could be apportioned between different instruments or systems. In 1858, Joseph Lister studied the cause of blood coagulation and inflammation that resulted after previous injuries and he later discovered and implemented antiseptics in the operating room, and as a result decreases death rate from surgery by a substantial amount. The Physiological Society was founded in London in 1876 as a dining club, the American Physiological Society is a nonprofit organization that was founded in 1887. The Society is, devoted to fostering education, scientific research, in 1891, Ivan Pavlov performed research on conditional reflexes that involved dogs saliva production in response to a plethora of sounds and visual stimuli
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Grid illusion
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A grid illusion is any kind of grid that deceives a persons vision. The two most common types of illusions are the Hermann grid illusion and the scintillating grid illusion. The Hermann grid illusion is an optical illusion reported by Ludimar Hermann in 1870, the illusion is characterized by ghostlike grey blobs perceived at the intersections of a white grid on a black background. The grey blobs disappear when looking directly at an intersection and this illusion can be observed in the Flag of Cornwall. The scintillating grid illusion is an illusion, discovered by E. Lingelbach in 1994. It is constructed by superimposing white discs on the intersections of orthogonal gray bars on a black background, dark dots seem to appear and disappear rapidly at random intersections, hence the label scintillating. When a person keeps his or her eyes directly on a single intersection, the dark dots disappear if one is too close to or too far from the image. Since they are so similar, the two names are used interchangeably. This requirement suggests the participation of global processes of the kind proposed for the linking and grouping of features in an image, the effect of both optical illusions is often explained by a neural process called lateral inhibition. A retinal ganglion cell pools the inputs of several photoreceptors over an area of retina, in the center of the receptive field the individual photoreceptors excite the ganglion cell when they detect increased luminance. The photoreceptors in the surrounding area inhibit the ganglion cell, thus, since a point at an intersection is surrounded by more intensity than a point at the middle of a line, the intersection appears darker due to the increased inhibition. There is strong evidence that the retinal ganglion cell theory is untenable, for example, making the lines of the grid wavy rather than straight eliminates both the Hermann grid and scintillating grid illusions. The Baumgartner / RGC theory does not predict this outcome, lateral inhibition theory also can not account for the fact that the Hermann grid illusion is perceived over a range of bar widths. Lateral inhibition theory would predict that decreasing the size of the grid would eradicate the illusory effect, one alternative explanation is that the illusion is due to S1 type simple cells in the visual cortex
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Lateral inhibition
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In neurobiology, lateral inhibition is the capacity of an excited neuron to reduce the activity of its neighbors. Lateral inhibition disables the spreading of action potentials from excited neurons to neighboring neurons in the lateral direction and this creates a contrast in stimulation that allows increased sensory perception. It is also referred to as lateral antagonism and occurs primarily in visual processes, but also in tactile, auditory, cells that utilize lateral inhibition appear primarily in the cerebral cortex and thalamus and make up lateral inhibitory networks. Artificial lateral inhibition has been incorporated into artificial sensory systems, such as chips, hearing systems. An often under-appreciated point is that lateral inhibition is visualised in a spatial sense. This refers to lateral inhibition between neurons that are not adjacent in a sense, but in terms of modality of stimulus. This phenomenon is thought to aid in colour discrimination, the concept of neural inhibition was well known to Descartes and his contemporaries. Sensory inhibition in vision was inferred by Ernst Mach in 1865 as depicted in his mach band, Inhibition in single sensory neurons was discovered and investigated starting in 1949 by Haldan K. Hartline when he used logarithms to express the effect of Ganglion receptive fields. His algorithms also help explain the experiment conducted by David H. Hubel and Torsten Wiesel that expressed a variation of sensory processing, including lateral inhibition, within different species. In 1956, Hartline revisited this concept of lateral inhibition in horseshoe crab eyes, during an experiment conducted with the aid of Henry G Wagner, Hartline explored the anatomy of ommatidia in the horseshoe crab because of their similar function and physiological anatomy to photoreceptors in the human eye. Also, they are larger than photoreceptors in humans, which would make them much easier to observe. Hartline contrasted the response signal of the ommatidium when a concentrated beam of light was directed at one receptor unit as opposed to three surrounding units. He further supported his theory of lateral inhibition as the signal of one unit was stronger when the surrounding units were not exposed to light. Georg von Békésy, in his book Sensory Inhibition, explores a range of inhibitory phenomena in sensory systems. Lateral inhibition increases the contrast and sharpness in visual response and this phenomenon occurs in the mammalian retina, for example. In the dark, a light stimulus will enhance the different photoreceptors. The rods in the center of the stimulus will transduce the signal to the brain. This contrast between the light and dark creates a sharper image and this mechanism also creates the Mach band visual effect
21.
Empirical theory of perception
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An empirical theory of perception is a kind of explanation for how percepts arise. Visual perception is initiated when objects in the world reflect light rays towards the eye, most empirical theories of visual perception begin with the observation that stimulation of the retina is fundamentally ambiguous. In empirical accounts, the most commonly proposed mechanism for circumventing this ambiguity is unconscious inference, descartes extended and refined this account. For Helmholtz Berkeleyan associations form the premises for inductive judgements, in Alhazens sense of the term, Helmholtz was one of the first thinkers on the subject to augment his reasoning with detailed knowledge of the anatomy of sensory mechanisms. In current work Helmholtzs use of the term is construed as referring to some mechanism that augments sense impressions with acquired knowledge or through application of heuristics, a recurring theme in these theories is that stimulus ambiguity is rectified by a priori knowledge about the natural world. On the wholly empirical account, this strategy determines qualities of perception in all visual domains, the wholly empirical theory of perception departs from many other empirical theories by recognizing the seriousness of the optical inverse problem. To illustrate this problem, imagine that three hoses are used to fill a bucket with water, if how much water each hose has contributed is known, it is straightforward to calculate how much water is in the bucket. These kinds of problems are known as “forward” problems, and scientists like them because they are easy to solve and this is a simple example of an inverse problem. Solutions to these problems are rarely possible, although they can sometimes be approximated by imposing assumption-based constraints on the “solution space”, navigating the world on the basis of sensory stimulation alone represents an inverse problem in the realm of biology. Consider, for example, the case of the distance and line length, when light reflected from a linear object falls on the retina, the object in 3-D space is transformed into a two-dimensional line. Note, however, that a distant line can form the image on the retina as a shorter. All the eyes receive is an image, which is analogous to the bucket of water. It is impossible to go backwards to know the distance, length. Despite this fact, percipients usually manage to behave effectively in response to sensory stimulation, the inverse optics problem presents a quandary for traditional approaches to perception. The wholly empirical approach holds that this experience is the determinant of perceptual qualities. The reason percipients see an object as dark or light, the argument goes, is that in both our own past and the past of the species it paid off to see it that particular way. Returning to the analogy, imagine that each of the three hoses pumps out water of a different color, one pumps out black water, one pumps out gray water. All one sees is the water in the bucket, which can be clear, gray, black, as expected, it is impossible to perform some calculation on the color of the water in the bucket to find out how much water came out of each hose
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Pareidolia
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Pareidolia is a psychological phenomenon in which the mind responds to a stimulus by perceiving a familiar pattern where none exists. The word derives from the Greek words para and the noun eidōlon, pareidolia can cause people to interpret random images, or patterns of light and shadow, as faces. This activation is similar to a faster time that is seen for images of real faces. The authors suggest that face perception evoked by face-like objects is an early process. An fMRI study in 2011 similarly showed that repeated presentation of visual shapes that were interpreted as meaningful led to decreased fMRI responses for real objects. These results indicate that the interpretation of ambiguous stimuli depends upon processes similar to those elicited by known objects and these studies help to explain why people identify a few circles and a line as a face so quickly and without hesitation. The stick figure face, despite its simplicity, conveys mood information and it would be just as simple to draw a stick figure face that would be perceived as hostile and aggressive. This ability, though highly specialized for the processing and recognition of human emotions, rocks may come to mimic recognizable forms through the random processes of formation, weathering and erosion. Most often, the scale of the rock is larger than the object it resembles. Well-meaning people with a new interest in fossils can pick up chert nodules, concretions or pebbles resembling bones, skulls, turtle shells, dinosaur eggs, etc. in both size and shape. Except for a growth in stature from 3.5 mm to 1,700 mm. Okamuras research earned him an Ig Nobel Prize in biodiversity in 1996, the Rorschach inkblot test uses pareidolia in an attempt to gain insight into a persons mental state. The Rorschach is a projective test, as it elicits the thoughts or feelings of respondents that are projected onto the ambiguous inkblot images. Projection in this instance is a form of directed pareidolia, there have been many instances of perceptions of religious imagery and themes, especially the faces of religious figures, in ordinary phenomena. Publicity surrounding sightings of figures and other surprising images in ordinary objects has spawned a market for such items on online auctions like eBay. One famous instance was a cheese sandwich with the face of the Virgin Mary. Pareidolia also arises in computer vision, specifically in image recognition programs, in the case of an artificial neural network, higher-level features correspond to more recognizable features, and enhancing these features brings out what the computer sees. These reflect the set of images that the network has seen previously. Striking visuals can be produced in this way, notably in the DeepDream software, various European ancient divination practices involved the interpretation of shadows cast by objects
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Neptune's Grotto
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Neptunes Grotto is a stalactite cave near the town of Alghero on the island of Sardinia, Italy. The cave was discovered by fishermen in the 18th century and has since developed into a popular tourist attraction. The grotto gets its name from the Roman god of the sea, the entrance to the grotto lies only around a metre above the sea level at the foot of the 110-metre-high Capo Caccia cliffs and the cave can therefore only be visited when the waters below are calm. A stairway cut into the cliff in 1954, the 654-step escala del cabirol, the grotto is also accessible via a short boat trip from the port of Alghero, these trips are arranged hourly during the summer, but less frequently during spring and autumn. Two other grottoes lie nearby, the Green grotto, which is not open to tourists, and the Grotta di Ricami, the combined length of the cave system is estimated to be around 4 kilometers, but only a few hundred metres are accessible to the public. Inside are passages of lit stalactite and stalagmite formations, and a 120-metre-long saltwater lake, the cave was once a habitat for the Mediterranean monk seal, which has become extinct in the area. Tourists visiting Neptunes Grotto are given guided tours and led single-file through a lit pathway, with tour guides providing information about the cave in Italian, the grotto is widely visited, and during the peak tourist season in August, can contain around 200 people at a time. Neptunes Grotto was the set of the movie Island of the Fishmen, for approximately two months the Grotto was transformed into a gigantic set. The science fiction movie starred Barbara Bach, and was under the direction of Sergio Martino, nereo Cave List of caves List of caves in Italy Article about the Neptune Cave Media related to Neptunes Grotto at Wikimedia Commons
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Stalactite
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A stalactite is a type of formation that hangs from the ceiling of caves, hot springs, or manmade structures such as bridges and mines. Any material which is soluble, can be deposited as a colloid, or is in suspension, or is capable of being melted, Stalactites may be composed of amberat, lava, minerals, mud, peat, pitch, sand, and sinter. A stalactite is not necessarily a speleothem, though speleothems are the most common form of stalactite because of the abundance of limestone caves, the corresponding formation on the floor of the cave is known as a stalagmite. The most common stalactites are speleothems, which occur in limestone caves and they form through deposition of calcium carbonate and other minerals, which is precipitated from mineralized water solutions. Limestone is the form of calcium carbonate rock which is dissolved by water that contains carbon dioxide. When the solution comes into contact with air the chemical reaction that created it is reversed, the reversed reaction is, Ca 2 → CaCO3 + H 2O + CO2 An average growth rate is 0.13 mm a year. The quickest growing stalactites are formed by a constant supply of slow dripping water rich in calcium carbonate and carbon dioxide. The drip rate must be enough to allow the CO2 to degas from the solution into the cave atmosphere. Too fast a drip rate and the solution, still carrying most of the CaCO3, falls to the floor where degassing occurs. All limestone stalactites begin with a single drop of water. When the drop falls, it deposits the thinnest ring of calcite, each subsequent drop that forms and falls deposits another calcite ring. Eventually, these form a very narrow, hollow tube commonly known as a soda straw stalactite. Soda straws can grow long, but are very fragile. If they become plugged by debris, water flowing over the outside, depositing more calcite. The same water drops that fall from the tip of a stalactite deposit more calcite on the floor below, unlike stalactites, stalagmites never start out as hollow soda straws. Given enough time, these formations can meet and fuse to create pillars of calcium carbonate known as a column, another type of stalactite is formed in lava tubes while lava is still active inside. The mechanism of formation is similar to that of limestone stalactites, a key difference with lava stalactites is that once the lava has ceased flowing, so too will the stalactites cease to grow. This means that if the stalactite were to be broken it would never grow back, the generic term lavacicle has been applied to lava stalactites and stalagmites indiscriminately and evolved from the word icicle
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Alghero
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Alghero, is a town of about 44,000 inhabitants in the Italian insular province of Sassari in northwestern Sardinia, next to the Mediterranean Sea. Part of its population descends from Catalan conquerors from the end of the Middle Ages and that is why the Catalan language is co-official in the city, unique in Italy, taking the name of alguerès dialect. The name Alghero comes from the medieval Latin Aleguerium, meaning stagnation of algae, Alghero is the fifth university center in the island, coming after Cagliari and Sassari. It hosts the headquarters of the Università degli Studi di Sassari’s Architecture, in 2012 it was the 10th most visited city by tourists in Italy. For ecclesiastical history, see Roman Catholic Diocese of Alghero-Bosa The area of todays Alghero has been settled since pre-historic times, the Ozieri culture was present here in the 4th millennium BC, while the Nuraghe civilization settled in the area around 1,500 BC. Due to its position on the Mediterranean Sea, Alghero had been developed into a fortified port town by 1102. The Dorias ruled Alghero for centuries, apart from a period under the rule of Pisa between 1283–84. Algheros population later grew because of the arrival of Catalan colonists, in the early 16th century Alghero received papal recognition as a bishopric and the status of Kings City and developed economically. It is uncertain whether this was some settlement, perhaps linked to the events of the Saracen invasions. For two centuries remained in the orbit of the Maritime Republics, as in 1283 when the Pisans were able to control it for a year. These were granted enticing privileges, and in fact replaced the original population, poorly spoken by young people, trying for some time to protect this dialect, through education programs and official use within the local authority. The city, one of the principal of Sardinia and the fifth most populated region, is one of the gateways to the Island and it a strong tourist popular destination in the island, in 2012 it was the 10th Italian cities most visited by foreign tourists. The Aragonese were followed by the Spanish Habsburgs, who ruled until 1702, in 1720 Alghero, along with the rest of Sardinia, was handed over to the Piedmont-based House of Savoy. In 1821 a famine led to a revolt by the population, at the end of the same century Alghero was de-militarised. During the Fascist era, part of the marshes were reclaimed. During World War II Alghero was bombed, and its historical centre suffered heavy damage, the presence of malaria in the countryside was finally overcome in the 1950s. Since then, Alghero has become a popular tourist resort, Alghero is located in the northwestern coast of Sardinia, along the bay named after the city. In the north of the area there is the Nurra plain, to the NW the karstic systems of Capo Caccia, Punta Giglio
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Sardinia
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Sardinia is the second largest island in the Mediterranean Sea and an autonomous region of Italy. It is located in the Western Mediterranean, just south of the French island of Corsica, the regions official name is Regione Autonoma della Sardegna / Regione Autònoma de Sardigna, and its capital and largest city is Cagliari. It is divided into four provinces and a metropolitan city and its indigenous language and the other minority languages spoken by the Sardinians enjoy equal dignity with Italian under regional law. The name Sardinia is from the pre-Roman noun *srd-, later romanised as sardus and it makes its first appearance on the Nora Stone, where the word Šrdn testifies to the names existence when the Phoenician merchants first arrived. According to Timaeus, one of Platos dialogues, Sardinia and its people as well might have named after Sardò. There has also been speculation that identifies the ancient Nuragic Sards with the Sherden, in Classical antiquity, Sardinia was called Ichnusa, Σανδάλιον Sandal, Sardinia and Sardó. Sardinia is the second-largest island in the Mediterranean Sea, with an area of 24,100 square kilometres and it is situated between 38°51 and 41°18 latitude north and 8°8 and 9°50 east longitude. To the west of Sardinia is the Sea of Sardinia, a unit of the Mediterranean Sea, to Sardinias east is the Tyrrhenian Sea, the nearest land masses are the island of Corsica, the Italian Peninsula, Sicily, Tunisia, the Balearic Islands, and Provence. The Tyrrhenian Sea portion of the Mediterranean Sea is directly to the east of Sardinia between the Sardinian east coast and the west coast of the Italian mainland peninsula, the Strait of Bonifacio is directly north of Sardinia and separates Sardinia from the French island of Corsica. The island has an ancient geoformation and, unlike Sicily and mainland Italy, is not earthquake-prone and its rocks date in fact from the Palaeozoic Era. Due to long erosion processes, the highlands, formed of granite, schist, trachyte, basalt, sandstone and dolomite limestone. The highest peak is Punta La Marmora, part of the Gennargentu Ranges in the centre of the island. The islands ranges and plateaux are separated by wide valleys and flatlands. Sardinia has few rivers, the largest being the Tirso,151 km long, which flows into the Sea of Sardinia, the Coghinas. There are 54 artificial lakes and dams that supply water and electricity, the main ones are Lake Omodeo and Lake Coghinas. The only natural lake is Lago di Baratz. A number of large, shallow, salt-water lagoons and pools are located along the 1,850 km of the coastline, the climate of the island is variable from area to area, due to several factors including the extension in latitude and the elevation. During the year there is a concentration of rainfall in the winter and autumn, some heavy showers in the spring
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Germany
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Germany, officially the Federal Republic of Germany, is a federal parliamentary republic in central-western Europe. It includes 16 constituent states, covers an area of 357,021 square kilometres, with about 82 million inhabitants, Germany is the most populous member state of the European Union. After the United States, it is the second most popular destination in the world. Germanys capital and largest metropolis is Berlin, while its largest conurbation is the Ruhr, other major cities include Hamburg, Munich, Cologne, Frankfurt, Stuttgart, Düsseldorf and Leipzig. Various Germanic tribes have inhabited the northern parts of modern Germany since classical antiquity, a region named Germania was documented before 100 AD. During the Migration Period the Germanic tribes expanded southward, beginning in the 10th century, German territories formed a central part of the Holy Roman Empire. During the 16th century, northern German regions became the centre of the Protestant Reformation, in 1871, Germany became a nation state when most of the German states unified into the Prussian-dominated German Empire. After World War I and the German Revolution of 1918–1919, the Empire was replaced by the parliamentary Weimar Republic, the establishment of the national socialist dictatorship in 1933 led to World War II and the Holocaust. After a period of Allied occupation, two German states were founded, the Federal Republic of Germany and the German Democratic Republic, in 1990, the country was reunified. In the 21st century, Germany is a power and has the worlds fourth-largest economy by nominal GDP. As a global leader in industrial and technological sectors, it is both the worlds third-largest exporter and importer of goods. Germany is a country with a very high standard of living sustained by a skilled. It upholds a social security and universal health system, environmental protection. Germany was a member of the European Economic Community in 1957. It is part of the Schengen Area, and became a co-founder of the Eurozone in 1999, Germany is a member of the United Nations, NATO, the G8, the G20, and the OECD. The national military expenditure is the 9th highest in the world, the English word Germany derives from the Latin Germania, which came into use after Julius Caesar adopted it for the peoples east of the Rhine. This in turn descends from Proto-Germanic *þiudiskaz popular, derived from *þeudō, descended from Proto-Indo-European *tewtéh₂- people, the discovery of the Mauer 1 mandible shows that ancient humans were present in Germany at least 600,000 years ago. The oldest complete hunting weapons found anywhere in the world were discovered in a mine in Schöningen where three 380, 000-year-old wooden javelins were unearthed
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Hermann von Helmholtz
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Hermann Ludwig Ferdinand von Helmholtz was a German physician and physicist who made significant contributions in several scientific fields. The largest German association of institutions, the Helmholtz Association, is named after him. In physics, he is known for his theories on the conservation of energy, work in electrodynamics, chemical thermodynamics, Helmholtzs work is influenced by the philosophy of Johann Gottlieb Fichte and Immanuel Kant. He tried to trace their theories in empirical matters like physiology, as a young man, Helmholtz was interested in natural science, but his father wanted him to study medicine at the Charité because there was financial support for medical students. Trained primarily in physiology, Helmholtz wrote on other topics, ranging from theoretical physics, to the age of the Earth. Helmholtzs first academic position was as a teacher of Anatomy at the Academy of Arts in Berlin in 1848 and he then moved to take a post of associate professor of physiology at the Prussian University of Königsberg, where he was appointed in 1849. In 1855 he accepted a professorship of anatomy and physiology at the University of Bonn. He was not particularly happy in Bonn, however, and three later he transferred to the University of Heidelberg, in Baden, where he served as professor of physiology. In 1871 he accepted his final university position, as professor of physics at the University of Berlin and his first important scientific achievement, an 1847 treatise on the conservation of energy, was written in the context of his medical studies and philosophical background. He discovered the principle of conservation of energy while studying muscle metabolism and he tried to demonstrate that no energy is lost in muscle movement, motivated by the implication that there were no vital forces necessary to move a muscle. This was a rejection of the tradition of Naturphilosophie which was at that time a dominant philosophical paradigm in German physiology. He published his theories in his book Über die Erhaltung der Kraft, in the 1850s and 60s, building on the publications of William Thomson, Helmholtz and William Rankine popularized the idea of the heat death of the universe. In fluid dynamics, Helmholtz made several contributions, including Helmholtzs theorems for vortex dynamics in inviscid fluids, Helmholtz was a pioneer in the scientific study of human vision and audition. He coined the term psychophysics, to capture the distinction between the measurement of physical stimuli and their effect on human perception. The physical sound needs to be increased exponentially in order for equal steps to seem linear, Helmholtz paved the way in experimental studies on the relationship between the physical energy and its appreciation, with the goal in mind to develop psychophysical laws. The sensory physiology of Helmholtz was the basis of the work of Wilhelm Wundt, a student of Helmholtz and he, more explicitly than Helmholtz, described his research as a form of empirical philosophy and as a study of the mind as something separate. Helmholtz had, in his early repudiation of Naturphilosophie, stressed the importance of materialism, in 1851, Helmholtz revolutionized the field of ophthalmology with the invention of the ophthalmoscope, an instrument used to examine the inside of the human eye. Helmholtzs interests at that time were focused on the physiology of the senses
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Ambiguous image
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Ambiguous images or reversible figures are optical illusion images which exploit graphical similarities and other properties of visual system interpretation between two or more distinct image forms. These are famous for inducing the phenomenon of multistable perception, multistable perception is the occurrence of an image being able to provide multiple, although stable, perceptions. Classic examples of this are the rabbit-duck and the Rubin vase, ambiguous images are important to the field of psychology because they are often research tools used in experiments. There is varying evidence on whether ambiguous images can be represented mentally, the rabbit-duck image seems to be one of the earliest of this type, first published in Fliegende Blätter, a German humor magazine. Middle vision is the stage in visual processing that combines all the features in the scene into distinct. This stage of vision comes before high-level vision and after early vision, when perceiving and recognizing images, mid-level vision comes into use when we need to classify the object we are seeing. Higher-level vision is used when the object classified must now be recognized as a member of its group. For example, through mid-level vision we perceive a face, then through high-level vision we recognize a face of a familiar person, mid-level vision and high-level vision are crucial for understanding a reality that is filled with ambiguous perceptual inputs. When we see an image, the first thing we do is attempt to organize all the parts of the scene into different groups, to do this, one of the most basic methods used is finding the edges. Edges can include obvious perceptions such as the edge of a house, when finding edges, the brains visual system detects a point on the image with a sharp contrast of lighting. Being able to detect the location of the edge of an object aids in recognizing the object, in ambiguous images, detecting edges still seems natural to the person perceiving the image. However, the brain undergoes deeper processing to resolve the ambiguity, for example, consider an image that involves an opposite change in magnitude of luminance between the object and the background. The opposing gradients will eventually come to a point where there is a degree of luminance of the object. At this point, there is no edge to be perceived, to counter this, the visual system connects the image as a whole rather than a set of edges, allowing one to see an object rather than edges and non-edges. Although there is no image to be seen, the brain is able to accomplish this because of its understanding of the physical world. In ambiguous images, an illusion is produced from illusory contours. An illusory contour is a perceived contour without the presence of a physical gradient and these illusory contours are processed by the brain in a similar way as real contours. The visual system accomplishes this by making inferences beyond the information that is presented in much the way as the luminance gradient
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Necker cube
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The Necker cube is an optical illusion first published as a rhomboid in 1832 by Swiss crystallographer Louis Albert Necker. It is a simple drawing of a cube with no visual cues as to its orientation. Necker cube is used in studies of visual perception. The Necker cube is a line drawing. The effect is interesting because each part of the picture is ambiguous by itself, the Necker cube is sometimes used to test computer models of the human visual system to see whether they can arrive at consistent interpretations of the image the same way humans do. Humans do not usually see an inconsistent interpretation of the cube, a cube whose edges cross in an inconsistent way is an example of an impossible object, specifically an impossible cube. With the cube on the left, most people see the face as being in front most of the time. Another reason behind this may be due to the natural preference of viewing things from left to right. There is evidence that by focusing on different parts of the one can force a more stable perception of the cube. The intersection of the two faces that are parallel to the forms a rectangle, and the lines that converge on the square form a y-junction at the two diagonally opposite sides. If an observer focuses on the upper y-junction the lower left face will appear to be in front, the upper right face will appear to be in front if the eyes focus on the lower junction. Blinking while being on the second perception will probably cause you to switch to the first one, the Necker cube has shed light on the human visual system. The phenomenon has served as evidence of the brain being a neural network with two distinct equally possible interchangeable stable states. The orientation of the Necker cube can also be altered by shifting the point of view. When seen from apparent above, one tends to be seen closer, and in contrast, when seen from a subjective viewpoint that is below. The Necker cube is used to illustrate how vampires in the science fiction novels Blindsight, one of the pieces of evidence is that vampires can see both interpretations of the Necker Cube simultaneously which sets them apart from baseline humanity. Optical illusion Penrose triangle Spinning Dancer Blivet Impossible cube Rhombille tiling Ward, Emily J. Scholl, seemingly Random Perceptual Switching in Bistable Events Triggered by Transient Unconscious Cues. Journal of Experimental Psychology, Human Perception and Performance, the viewing-from-above bias and the silhouette illusion
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Rubin vase
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Rubins vase is a famous set of ambiguous or bi-stable two-dimensional forms developed around 1915 by the Danish psychologist Edgar Rubin. The visual effect generally presents the viewer with two interpretations, each of which is consistent with the retinal image, but only one of which can be maintained at a given moment. This is because the bounding contour will be seen as belonging to the figure shape, if the latter region is interpreted instead as the figure, then the same bounding contour will be seen as belonging to it. These types of stimuli are both interesting and useful because they provide an excellent and intuitive demonstration of the distinction the brain makes during visual perception. Normally the brain classifies images by which object surrounds which – establishing depth, if one object surrounds another object, the surrounded object is seen as figure, and the presumably further away object is the ground, and vice versa. This makes sense, since if a piece of fruit is lying on the ground, one would want to pay attention to the figure, the distinction is exploited by devising an ambiguous picture, whose contours match seamlessly the contours of another picture. The picture should be flat and have little texture to it, the stereotypical example has a vase in the center, and a face matching its contour. A Psychology of Picture Perception, John M. Kennedy,1974, Jossey-Bass Publishers, ISBN 0-87589-204-3 The art and science of visual illusions, Nicholas Wade. 1982 Routledge & Kegan Paul Ltd, ISBN 0-7100-0868-6 Visual Space Perception, William H. Ittelson. 1969, Springer Publishing Company, LOCCCN 60-15818 Vase or face, a neural correlates of shape-selective grouping processes in the human brain. Uri Hasson, Talma Hendler, Dafna Ben Bashat, Rafael Malach, journal of Cognitive Neuroscience, Vol 13, Aug 2001. ISSN 0898-929X Rubins People Inside the Wall People trapped inside a Wall Illusionworks. com article Rubin has invented nothing The Rubins vase before Rubin
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Geometrical-optical illusions
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Geometrical-optical illusions are visual illusions, also optical illusions, in which the geometrical properties of what is seen differ from those of the corresponding objects in the visual field. In studying geometry one concentrates on the position of points and on the length, orientation, geometrical-optical illusions then relate in the first instance to object characteristics as defined by geometry. Though vision is three-dimensional, in many situations depth can be factored out, whereas their counterparts in the observers object space are public and have measurable properties, the illusions themselves are private to the observers experience. Nevertheless, they are accessible to portrayal by verbal and other communication, a nulling technique is particularly useful in which a target is deliberately given an opposing deformation in an effort to cancel the illusion. Visual or Optical Illusions can be categorized according to the nature of the difference between objects and percepts, for example, these can be in brightness or color, called intensive properties of targets, e. g. Mach bands. Or they can be in their location, size, orientation or depth, when an illusion involves properties that fall within the purview of geometry it is geometrical-optical, a term given to it in the first scientific paper devoted to the topic by J. J. Oppel, a German high-school teacher, in 1854 and it was taken up by W. Wundt, widely regarded as the founder of experimental psychology, and is now universally used, see the several comprehensive treatises devoted to the subject. That by 1972 the first edition of Robinsons book devotes 100 closely printed pages, the easiest to explore are the geometrical-optical illusions that show up in ordinary black and white line drawings. A few examples are drawn from the list of optical illusions, visual illusions proper should be distinguished from some related phenomena. Some simple targets such as the Necker Cube are capable of more than one interpretation and they may be called ambiguous configurations rather than illusion, because what is seen at any time is not actually illusory. The configurations of the Penrose or Escher type are illusory in the sense that only on a logical analysis it becomes apparent that they are not physically realizable. Some components of geometrical-optical illusions can be ascribed to aberrations at that level, even if this does not fully account for an illusion, the step is helpful because it puts elaborate mental theories in a more secure place. The moon illusion is a good example, before invoking concepts of apparent distance and size constancy, it helps to be sure that the retinal image hasnt changed much when the moon looks larger as it descends to the horizon. Once the signals from the retina enter the visual cortex, a host of local interactions are known to take place, in particular, neurons are tuned to target orientation and their response are known to depend on context. The widely accepted interpretation of, e. g. However, the subject, therefore, is a fertile field for propositions based in the disciplines of perception and cognition. A barrel lying within the rails would have to be wider to cover the increased portion of the width of the track if it were farther away. The consequence is the judgment that the barrels differ in diameter, a scientific study will include the recognition that a representation of the visual word is embodied in the state of the organisms nervous system at the time the illusion is experienced. Such a concept is to be distinguished from the approach which would look for aberrations that are imposed on the input in its path through the sensory apparatus
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Penrose triangle
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The Penrose triangle, also known as the Penrose tribar, or the impossible tribar, is an impossible object. It was first created by the Swedish artist Oscar Reutersvärd in 1934, the psychiatrist Lionel Penrose and his mathematician son Roger Penrose independently devised and popularized it in the 1950s, describing it as impossibility in its purest form. It is featured prominently in the works of artist M. C, Escher, whose earlier depictions of impossible objects partly inspired it. The tribar appears to be an object, made of three straight beams of square cross-section which meet pairwise at right angles at the vertices of the triangle they form. The beams may be broken, forming cubes or cuboids and this combination of properties cannot be realized by any 3-dimensional object in ordinary Euclidean space. Such an object can exist in certain Euclidean 3-manifolds, there also exist 3-dimensional solid shapes each of which, when viewed from a certain angle, appears the same as the 2-dimensional depiction of the Penrose triangle on this page. The term Penrose triangle can refer to the 2-dimensional depiction or the object itself. Eschers lithograph Waterfall depicts a watercourse that flows in a zigzag along the sides of two elongated Penrose triangles, so that it ends up two stories higher than it began. The resulting waterfall, forming the sides of both triangles, drives a water wheel. Escher helpfully points out that in order to keep the wheel turning some water must occasionally be added to compensate for evaporation, if a line is traced around the Penrose triangle, a 3-loop Möbius strip is formed. Although the tribar is named one of the objects, there exist many more that fit into the same category. Other impossible objects include the devils fork, the dancing elephant, three hares Penrose steps Penrose square root law An article about impossible triangle sculpture in Perth Escher for Real constructions
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Penrose staircase
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The Penrose stairs or Penrose steps, also dubbed the impossible staircase, is an impossible object created by Lionel Penrose and his son Roger Penrose. This is clearly impossible in three dimensions, Escher then discovered the Penrose stairs in the following year and made his now famous lithograph Klimmen en dalen in March 1960. Penrose and Escher were informed of others work that same year. Escher developed the theme further in his print Waterval, which appeared in 1961, Escher, in the 1950s, had not yet drawn any impossible figures and was not aware of their existence. Roger Penrose had been introduced to Eschers work at the International Congress of Mathematicians in Amsterdam in 1954 and he was absolutely spellbound by Eschers work, and on his journey back to England he decided to produce something impossible on his own. After experimenting with designs of bars overlying each other he finally arrived at the impossible triangle. Roger showed his drawings to his father, who produced several variants. They wanted to publish their findings but did not know in what field the subject belonged, because Lionel Penrose knew the editor of the British Journal of Psychology and convinced him to publish their short manuscript, the finding was finally presented as a psychological subject. After the publication in 1958 the Penroses sent a copy of the article to Escher as a token of their esteem, form a closed, circular construction, rather like a snake biting its own tail. And yet they can be drawn in perspective, each step higher than the previous one. I discovered the principle in an article which was sent to me, but I was not familiar with the continuous steps of which the author had included a clear, if perfunctory, sketch, although I was employing some of his other examples. Escher was captivated by the stairs and subsequently wrote a letter to the Penroses in April 1960, A few months ago. Should you have published articles on impossible objects or related topics, or should you know of any such articles. The staircase design had been discovered previously by the Swedish artist Oscar Reutersvärd and he did not realize that his figure was a continuous flight of stairs while drawing, but the process enabled him to trace his increasingly complex designs step by step. Eschers Ascending and Descending was sent to Reutersvärd in 1961, he was impressed, throughout the 1960s, Reutersvärd sent several letters to Escher to express his admiration for his work, but the Dutch artist failed to respond. Roger Penrose only discovered Reutersvärds work in 1984, a Penrose stair appears in the 1986 movie Labyrinth. A Penrose stair appears in the 2010 movie Inception, in the game Monument Valley the player leads the princess Ida through mazes of optical illusions and impossible objects while manipulating the world around her to reach various platforms. The app PenroseStairs is a puzzle game on symmetric impossible staircases
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M. C. Escher
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Maurits Cornelis Escher, or commonly M. C. Escher, was a Dutch graphic artist who made mathematically inspired woodcuts, lithographs, early in his career, he drew inspiration from nature, making studies of insects, landscapes, and plants such as lichens, all of which he used as details in his artworks. Apart from being used in a variety of papers, his work has appeared on the covers of many books. He was one of the inspirations of Douglas Hofstadters 1979 book Gödel, Escher. Maurits Cornelis Escher was born on 17 June 1898 in Leeuwarden, Friesland and he was the youngest son of the civil engineer George Arnold Escher and his second wife, Sara Gleichman. In 1903, the moved to Arnhem, where he attended primary and secondary school until 1918. Known to his friends and family as Mauk, he was a sickly child, although he excelled at drawing, his grades were generally poor. He also took carpentry and piano lessons until he was thirteen years old, in 1918, he went to the Technical College of Delft. From 1919 to 1922, Escher attended the Haarlem School of Architecture and Decorative Arts, learning drawing and he briefly studied architecture, but he failed a number of subjects and switched to decorative arts, studying under the graphic artist Samuel Jessurun de Mesquita. In 1922, an important year of his life, Escher traveled through Italy, visiting Florence, San Gimignano, Volterra, Siena, in the same year he traveled through Spain, visiting Madrid, Toledo, and Granada. He was impressed by the Italian countryside, and in Granada by the Moorish architecture of the fourteenth-century Alhambra, Escher returned to Italy, and lived in Rome from 1923 to 1935. While in Italy, Escher met Jetta Umiker – a Swiss woman, the couple settled in Rome where their first son, Giorgio Arnaldo Escher, named after his grandfather, was born. Escher and Jetta later had two sons, Arthur and Jan. He travelled frequently, visiting Viterbo in 1926, the Abruzzi in 1927 and 1929, Corsica in 1928 and 1933, Calabria in 1930, the townscapes and landscapes of these places feature prominently in his artworks. In May and June 1936, Escher travelled back to Spain, revisiting the Alhambra, the sketches he made in the Alhambra formed a major source for his work from that time on. He also studied the architecture of the Mezquita, the Moorish mosque of Cordoba and this turned out to be the last of his long study journeys, after 1937, his artworks were created in his studio rather than in the field. All the same, even his work already shows his interest in the nature of space, the unusual, perspective. In 1935, the climate in Italy became unacceptable to Escher
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Ascending and Descending
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Ascending and Descending is a lithograph print by the Dutch artist M. C. Escher first printed in March 1960, the original print measures 14 in ×11 1⁄4 in. The lithograph depicts a large building roofed by a never-ending staircase, two lines of identically dressed men appear on the staircase, one line ascending while the other descends. Two figures sit apart from the people on the staircase, one in a secluded courtyard. While most two-dimensional artists use relative proportions to create an illusion of depth, Escher developed the theme further in his print Waterfall, which appeared in 1961. The two concentric processions on the stairs use enough people to emphasise the lack of vertical rise, in addition, the shortness of the tunics worn by the people makes it clear that some are stepping up and some are stepping down. The structure is embedded in human activity, by showing an unaccountable ritual of what Escher calls an unknown sect, Escher has added an air of mystery to the people who ascend and descend the stairs. Therefore, the stairs themselves tend to become incorporated into that mysterious appearance, there are free people and Escher said of these, recalcitrant individuals refuse, for the time being, to take part in the exercise of treading the stairs. They have no use for it at all, but no doubt, Escher suggests that not only the labours, but the very lives of these monk-like people are carried out in an inescapable, coercive and bizarre environment. Two earlier Escher pictures that feature stairs are House of Stairs and Relativity
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Waterfall (M. C. Escher)
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Waterfall is a lithograph by the Dutch artist M. C. Escher, first printed in October 1961. It shows a physically impossible perpetual motion machine where water from the base of a waterfall appears to run downhill along the path before reaching the top of the waterfall. While most two-dimensional artists use relative proportions to create an illusion of depth, the watercourse supplying the waterfall has the structure of two Penrose triangles. A Penrose triangle is an object designed by Oscar Reutersvärd in 1934. The image depicts a watermill with an aqueduct and waterwheel as the main feature. The aqueduct begins at the waterwheel and flows behind it, the walls of the aqueduct step downward, suggesting that it slopes downhill. The aqueduct turns sharply three times, first to the left, then forward and finally to the left again. The viewer looks down at the scene diagonally, which means that from the perspective the aqueduct appears to be slanted upward. The second left-hand turn is supported by pillars from the first, the two support towers continue above the aqueduct and are topped by two compound polyhedra, revealing Eschers interest in mathematics as an artist. The one on the left is a compound of three cubes, the one on the right is a stellation of a rhombic dodecahedron and is known as Eschers solid. Below the mill is a garden of bizarre, giant plants and this is actually a magnified view of a cluster of moss and lichen that Escher drew in ink as a study in 1942. The background seems to be an expanse of terraced farmland. Eschers Solid—from Wolfram MathWorld Eschers Solid Includes a great deal of metric data The Polyhedra of M. C
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Gestalt psychology
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Gestalt psychology or gestaltism is a philosophy of mind of the Berlin School of experimental psychology. Gestalt psychology is an attempt to understand the laws behind the ability to acquire, the central principle of gestalt psychology is that the mind forms a global whole with self-organizing tendencies. The assumed physiological mechanisms on which Gestalt theory rests are poorly defined, the Gestalt theory of perception has been criticized as being descriptive of the end products of perception without providing much insight into the processes that lead to perception. What happened to the Gestalt school that always aspired to provide a vision of psychology. Perhaps there is, in fact, little that holds the classic phenomena of Gestalt psychology together and this principle maintains that when the human mind forms a percept or gestalt, the whole has a reality of its own, independent of the parts. Koffka did not like the translation and he firmly corrected students who replaced other with greater. This is not a principle of addition he said, the whole has an independent existence. In the study of perception, Gestalt psychologists stipulate that perceptions are the products of complex interactions among various stimuli, contrary to the behaviorist approach to focusing on stimulus and response, gestalt psychologists sought to understand the organization of cognitive processes. In psychology, gestaltism is often opposed to structuralism, Gestalt theory, it is proposed, allows for the deconstruction of the whole situation into its elements. The concept of gestalt was first introduced in philosophy and psychology in 1890 by Christian von Ehrenfels, the idea of gestalt has its roots in theories by David Hume, Johann Wolfgang von Goethe, Immanuel Kant, David Hartley, and Ernst Mach. On the philosophical foundations of these ideas see Foundations of Gestalt Theory and this gestalt or whole form approach sought to define principles of perception—seemingly innate mental laws that determined the way objects were perceived. It is based on the here and now, and in the way things are seen, images can be divided into figure or ground. The question is what is perceived at first glance, the figure in front and these laws took several forms, such as the grouping of similar, or proximate, objects together, within this global process. The founders of Gestalt therapy, Fritz and Laura Perls, had worked with Kurt Goldstein, Laura Perls had been a Gestalt psychologist before she became a psychoanalyst and before she began developing Gestalt therapy together with Fritz Perls. The extent to which Gestalt psychology influenced Gestalt therapy is disputed, in any case it is not identical with Gestalt psychology. Thus, though recognizing the historical connection and the influence, most gestalt psychologists emphasize that gestalt therapy is not a form of gestalt psychology and his work has no substantive relation to scientific Gestalt psychology. There are clinical applications of Gestalt psychology in the field, foremost in Europe. The school of gestalt practiced a series of theoretical and methodological principles that attempted to redefine the approach to psychological research, principle of psychophysical isomorphism – A correlation exists between conscious experience and cerebral activity
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Illusory contours
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Illusory contours or subjective contours are visual illusions that evoke the perception of an edge without a luminance or color change across that edge. Illusory brightness and depth ordering frequently accompany illusory contours, friedrich Schumann is often credited with the discovery of illusory contours around the beginning of the twentieth century, however illusory contours are present in art dating to the Middle Ages. Gaetano Kanizsa’s 1976 Scientific American paper marks the resurgence of interest in illusory contours for vision scientists, Kanizsa Figures, Perhaps the most famous example of an illusory contour is the Pac-Man configuration popularized by Gaetano Kanizsa. Kanizsa figurers trigger the percept of a contour by aligning Pac-Man-shaped inducers in the visual field such that the edges form a shape. Though not explicitly part of the image, Kanizsa figures evoke the percept of a shape, typically, the shape seems brighter than the background though luminance is in reality homogeneous. Additionally, the illusory shape seem to be closer to the viewer than the inducers, Kanizsa figures involve modal completion of the illusory shape and amodal completion of the inducers. Closely related to Kanizsa figures is the Ehrenstein illusion, instead of employing Pac-Man inducers, the Ehrenstein illusion triggers an illusory contour percept via radial line segments. Ehrenstein’s discovery was originally contextualized as a modification of the Hermann grid, abutting Line Gratings, Illusory contours are also created at the boundary between two misaligned gratings. In these so-called abutting line gratings, the contour is perpendicular to the inducing elements. It is thought that early visual cortical regions such as V1 V2 are responsible for forming illusory contours, for example, objects in the natural world are often only partially visible. Illusory contours provide clues for how the visual system constructs surfaces when portions of the edge are not visible. Illusory contours figures Many unpublished drawings
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