Gustav Theodor Fechner was a German philosopher and experimental psychologist. An early pioneer in experimental psychology and founder of psychophysics, he inspired many 20th-century scientists and philosophers, he is credited with demonstrating the non-linear relationship between psychological sensation and the physical intensity of a stimulus via the formula: S = K ln I, which became known as the Weber–Fechner law. Fechner was born near Muskau, in Lower Lusatia, where his father was a pastor. Despite being raised by his religious father, Fechner became an atheist in life, he was educated first at Sorau. In 1817 he studied of medicine at the Medizinische Akademie Carl Gustav Carus in Dresden and from 1818 at the University of Leipzig, the city in which he spent the rest of his life, he earned his PhD from Leipzig in 1835. In 1834 he was appointed professor of physics, but in 1839, he contracted an eye disorder while studying the phenomena of color and vision, after much suffering, resigned. Subsequently recovering, he turned to the study of the mind and its relations with the body, giving public lectures on the subjects dealt with in his books.
Whilst lying in bed Fechner had an insight into the relationship between mental sensations and material sensations. This insight proved to be significant in the development of psychology as there was now a quantitative relationship between the mental and physical worlds. Fechner published chemical and physical papers, translated chemical works by Jean-Baptiste Biot and Louis Jacques Thénard from the French. A different but essential side of his character is seen in his poems and humorous pieces, such as the Vergleichende Anatomie der Engel, written under the pseudonym of "Dr. Mises." Fechner's epoch-making work was his Elemente der Psychophysik. He starts from the monistic thought that bodily facts and conscious facts, though not reducible one to the other, are different sides of one reality, his originality lies in trying to discover an exact mathematical relation between them. The most famous outcome of his inquiries is the law known as the Weber–Fechner law which may be expressed as follows: "In order that the intensity of a sensation may increase in arithmetical progression, the stimulus must increase in geometrical progression."Though holding good within certain limits only, the law has been found to be immensely useful.
Fechner's law implies that sensation is a logarithmic function of physical intensity, impossible due to the logarithm's singularity at zero. Fechner's general formula for getting at the number of units in any sensation is S = c log R, where S stands for the sensation, R for the stimulus numerically estimated, c for a constant that must be separately determined by experiment in each particular order of sensibility. Fechner's reasoning has been criticized on the grounds that although stimuli are composite, sensations are not. "Every sensation," says William James, "presents itself as an indivisible unit. In 1838, he studied the still-mysterious perceptual illusion of what is still called the Fechner color effect, whereby colors are seen in a moving pattern of black and white; the English journalist and amateur scientist Charles Benham, in 1894, enabled English-speakers to learn of the effect through the invention of the spinning top that bears his name. Whether Fechner and Benham actually met face to face for any reason is not known.
In 1878 Fechner published a paper. He delved into experimental aesthetics and thought to determine the shapes and dimensions of aesthetically pleasing objects, he used the sizes of paintings as his data base. In his 1876 Vorschule der Aesthetik he used the method of extreme ranks for subjective judgements. Fechner is credited with introducing the median into the formal analysis of data. In 1871 Fechner reported the first empirical survey of coloured letter photisms among 73 synesthetes, his work was followed in the 1880s by that of Francis Galton. One of Fechner's speculations about consciousness dealt with brain. During his time, it was known that the brain is bilaterally symmetrical and that there is a deep division between the two halves that are linked by a connecting band of fibers called the corpus callosum. Fechner speculated that if the corpus callosum were split, two separate streams of consciousness would result - the mind would become two. Yet, Fechner believed. During the mid-twentieth century, Roger Sperry and Michael Gazzaniga worked on epileptic patients with sectioned corpus callosum and observed that Fechner's idea was correct.
Fechner constructed ten rectangles with different ratios of width to length and asked numerous observers to choose the "best" and "worst" rectangle shape. He was concerned with the visual appeal of rectangles with different proportions. Participants were explicitly instructed to disregard any associations that they have with the rectangles, e.g. with objects of similar ratios. The rectangles chosen as "best" by the largest number of participants and as "worst" by the least number of participants had a ratio of 0.62. This ratio is known as the "golden section" and referred to the ratio of a rectangle's width to length, most appealing to the eye. Carl Stumpf was a p
The decibel is a unit of measurement used to express the ratio of one value of a power or field quantity to another on a logarithmic scale, the logarithmic quantity being called the power level or field level, respectively. It can be used to express a change in an absolute value. In the latter case, it expresses the ratio of a value to a fixed reference value. For example, if the reference value is 1 volt the suffix is "V", if the reference value is one milliwatt the suffix is "m". Two different scales are used when expressing a ratio in decibels, depending on the nature of the quantities: power and field; when expressing a power ratio, the number of decibels is ten times its logarithm to base 10. That is, a change in power by a factor of 10 corresponds to a 10 dB change in level; when expressing field quantities, a change in amplitude by a factor of 10 corresponds to a 20 dB change in level. The decibel scales differ by a factor of two so that the related power and field levels change by the same number of decibels in, for example, resistive loads.
The definition of the decibel is based on the measurement of power in telephony of the early 20th century in the Bell System in the United States. One decibel is one tenth of one bel, named in honor of Alexander Graham Bell. Today, the decibel is used for a wide variety of measurements in science and engineering, most prominently in acoustics and control theory. In electronics, the gains of amplifiers, attenuation of signals, signal-to-noise ratios are expressed in decibels. In the International System of Quantities, the decibel is defined as a unit of measurement for quantities of type level or level difference, which are defined as the logarithm of the ratio of power- or field-type quantities; the decibel originates from methods used to quantify signal loss in telegraph and telephone circuits. The unit for loss was Miles of Standard Cable. 1 MSC corresponded to the loss of power over a 1 mile length of standard telephone cable at a frequency of 5000 radians per second, matched the smallest attenuation detectable to the average listener.
The standard telephone cable implied was "a cable having uniformly distributed resistance of 88 Ohms per loop-mile and uniformly distributed shunt capacitance of 0.054 microfarads per mile". In 1924, Bell Telephone Laboratories received favorable response to a new unit definition among members of the International Advisory Committee on Long Distance Telephony in Europe and replaced the MSC with the Transmission Unit. 1 TU was defined such that the number of TUs was ten times the base-10 logarithm of the ratio of measured power to a reference power. The definition was conveniently chosen such that 1 TU approximated 1 MSC. In 1928, the Bell system renamed the TU into the decibel, being one tenth of a newly defined unit for the base-10 logarithm of the power ratio, it was named the bel, in honor of the telecommunications pioneer Alexander Graham Bell. The bel is used, as the decibel was the proposed working unit; the naming and early definition of the decibel is described in the NBS Standard's Yearbook of 1931: Since the earliest days of the telephone, the need for a unit in which to measure the transmission efficiency of telephone facilities has been recognized.
The introduction of cable in 1896 afforded a stable basis for a convenient unit and the "mile of standard" cable came into general use shortly thereafter. This unit was employed up to 1923 when a new unit was adopted as being more suitable for modern telephone work; the new transmission unit is used among the foreign telephone organizations and it was termed the "decibel" at the suggestion of the International Advisory Committee on Long Distance Telephony. The decibel may be defined by the statement that two amounts of power differ by 1 decibel when they are in the ratio of 100.1 and any two amounts of power differ by N decibels when they are in the ratio of 10N. The number of transmission units expressing the ratio of any two powers is therefore ten times the common logarithm of that ratio; this method of designating the gain or loss of power in telephone circuits permits direct addition or subtraction of the units expressing the efficiency of different parts of the circuit... In 1954, J. W. Horton argued that the use of the decibel as a unit for quantities other than transmission loss led to confusion, suggested the name'logit' for "standard magnitudes which combine by addition".
In April 2003, the International Committee for Weights and Measures considered a recommendation for the inclusion of the decibel in the International System of Units, but decided against the proposal. However, the decibel is recognized by other international bodies such as the International Electrotechnical Commission and International Organization for Standardization; the IEC permits the use of the decibel with field quantities as well as power and this recommendation is followed by many national standards bodies, such as NIST, which justifies the use of the decibel for voltage ratios. The term field quantity is deprecated by ISO 80000-1. In spite of their widespread use, suffixes are not recognized by the IEC or ISO. ISO 80000-3 describes definitions for units of space and time; the decibel for use in acoustics is defined in ISO 80000-8. The major difference from the article below is that for acoustics the decibel has no
International Standard Serial Number
An International Standard Serial Number is an eight-digit serial number used to uniquely identify a serial publication, such as a magazine. The ISSN is helpful in distinguishing between serials with the same title. ISSN are used in ordering, interlibrary loans, other practices in connection with serial literature; the ISSN system was first drafted as an International Organization for Standardization international standard in 1971 and published as ISO 3297 in 1975. ISO subcommittee TC 46/SC 9 is responsible for maintaining the standard; when a serial with the same content is published in more than one media type, a different ISSN is assigned to each media type. For example, many serials are published both in electronic media; the ISSN system refers to these types as electronic ISSN, respectively. Conversely, as defined in ISO 3297:2007, every serial in the ISSN system is assigned a linking ISSN the same as the ISSN assigned to the serial in its first published medium, which links together all ISSNs assigned to the serial in every medium.
The format of the ISSN is an eight digit code, divided by a hyphen into two four-digit numbers. As an integer number, it can be represented by the first seven digits; the last code digit, which may be 0-9 or an X, is a check digit. Formally, the general form of the ISSN code can be expressed as follows: NNNN-NNNC where N is in the set, a digit character, C is in; the ISSN of the journal Hearing Research, for example, is 0378-5955, where the final 5 is the check digit, C=5. To calculate the check digit, the following algorithm may be used: Calculate the sum of the first seven digits of the ISSN multiplied by its position in the number, counting from the right—that is, 8, 7, 6, 5, 4, 3, 2, respectively: 0 ⋅ 8 + 3 ⋅ 7 + 7 ⋅ 6 + 8 ⋅ 5 + 5 ⋅ 4 + 9 ⋅ 3 + 5 ⋅ 2 = 0 + 21 + 42 + 40 + 20 + 27 + 10 = 160 The modulus 11 of this sum is calculated. For calculations, an upper case X in the check digit position indicates a check digit of 10. To confirm the check digit, calculate the sum of all eight digits of the ISSN multiplied by its position in the number, counting from the right.
The modulus 11 of the sum must be 0. There is an online ISSN checker. ISSN codes are assigned by a network of ISSN National Centres located at national libraries and coordinated by the ISSN International Centre based in Paris; the International Centre is an intergovernmental organization created in 1974 through an agreement between UNESCO and the French government. The International Centre maintains a database of all ISSNs assigned worldwide, the ISDS Register otherwise known as the ISSN Register. At the end of 2016, the ISSN Register contained records for 1,943,572 items. ISSN and ISBN codes are similar in concept. An ISBN might be assigned for particular issues of a serial, in addition to the ISSN code for the serial as a whole. An ISSN, unlike the ISBN code, is an anonymous identifier associated with a serial title, containing no information as to the publisher or its location. For this reason a new ISSN is assigned to a serial each time it undergoes a major title change. Since the ISSN applies to an entire serial a new identifier, the Serial Item and Contribution Identifier, was built on top of it to allow references to specific volumes, articles, or other identifiable components.
Separate ISSNs are needed for serials in different media. Thus, the print and electronic media versions of a serial need separate ISSNs. A CD-ROM version and a web version of a serial require different ISSNs since two different media are involved. However, the same ISSN can be used for different file formats of the same online serial; this "media-oriented identification" of serials made sense in the 1970s. In the 1990s and onward, with personal computers, better screens, the Web, it makes sense to consider only content, independent of media; this "content-oriented identification" of serials was a repressed demand during a decade, but no ISSN update or initiative occurred. A natural extension for ISSN, the unique-identification of the articles in the serials, was the main demand application. An alternative serials' contents model arrived with the indecs Content Model and its application, the digital object identifier, as ISSN-independent initiative, consolidated in the 2000s. Only in 2007, ISSN-L was defined in the
Signal-to-noise ratio is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to the noise power expressed in decibels. A ratio higher than 1:1 indicates more signal than noise. While SNR is quoted for electrical signals, it can be applied to any form of signal, for example isotope levels in an ice core, biochemical signaling between cells, or financial trading signals. Signal-to-noise ratio is sometimes used metaphorically to refer to the ratio of useful information to false or irrelevant data in a conversation or exchange. For example, in online discussion forums and other online communities, off-topic posts and spam are regarded as "noise" that interferes with the "signal" of appropriate discussion; the signal-to-noise ratio, the bandwidth, the channel capacity of a communication channel are connected by the Shannon–Hartley theorem. Signal-to-noise ratio is defined as the ratio of the power of a signal to the power of background noise: S N R = P s i g n a l P n o i s e, where P is average power.
Both signal and noise power must be measured at the same or equivalent points in a system, within the same system bandwidth. Depending on whether the signal is a constant or a random variable, the signal to noise ratio for random noise N with expected value of zero becomes: S N R = s 2 σ N 2 or S N R = E σ N 2 where E refers to the expected value, i.e. in this case the mean of S 2. If the signal and the noise are measured across the same impedance, the SNR can be obtained by calculating the square of the amplitude ratio: S N R = P s i g n a l P n o i s e = 2, where A is root mean square amplitude; because many signals have a wide dynamic range, signals are expressed using the logarithmic decibel scale. Based upon the definition of decibel and noise may be expressed in decibels as P s i g n a l, d B = 10 log 10 and P n o i s e, d B = 10 log 10 . In a similar manner, SNR may be expressed in decibels as S N R d B = 10 log 10 . Using the definition of SNR S N R d B = 10 log 10 . Using the quotient rule for logarithms 10 log 10 = 10
Leipzig University, in Leipzig in the Free State of Saxony, Germany, is one of the world's oldest universities and the second-oldest university in Germany. The university was founded on December 2, 1409 by Frederick I, Elector of Saxony and his brother William II, Margrave of Meissen, comprised the four scholastic faculties. Since its inception, the university has engaged in teaching and research for over 600 years without interruption. Famous alumni include Leibniz, Leopold von Ranke, Friedrich Nietzsche, Robert Schumann, Richard Wagner, Tycho Brahe, Georgius Agricola, Angela Merkel and the nine Nobel laureates associated with the university; the university was modelled on the University of Prague, from which the German-speaking faculty members withdrew to Leipzig after the Jan Hus crisis and the Decree of Kutná Hora. The Alma mater Lipsiensis opened in 1409, after it had been endorsed by Pope Alexander V in his Bull of Acknowledgment on, its first rector was Johann von Münsterberg. From its foundation, the Paulinerkirche served as the university church.
After the Reformation, the church and the monastery buildings were donated to the university in 1544. In order to secure independent and sustainable funding, the university was endowed with the lordship over 9 villages east of Leipzig, it kept this status for nearly 400 years. As many European universities, the university of Leipzig was structured into colleges responsible for organising accommodation and collegiate lecturing. Among the colleges of Leipzig were the Small College, the Large College, the Red College, the College of our Lady and the Pauliner-College. There were private residential halls; the colleges had jurisdiction over their members. The college structure was abandoned and today only the names survive. During the first centuries, the university grew and was a rather regional institution; this changed, during the 19th century when the university became a world-class institution of higher education and research. At the end of the 19th century, important scholars such as Bernhard Windscheid and Wilhelm Ostwald taught at Leipzig.
Leipzig University was one of the first German universities to allow women to register as "guest students". At its general assembly in 1873, the Allgemeiner Deutscher Frauenverein thanked the University of Leipzig and Prague for allowing women to attend as guest students; this was the year that the first woman in Germany obtained Johanna von Evreinov. Until the beginning of the Second World War, Leipzig University attracted a number of renowned scholars and Nobel Prize laureates, including Paul Ehrlich, Felix Bloch, Werner Heisenberg and Sin-Itiro Tomonaga. Many of the university's alumni became important scientists. Under Nazi rule many Jews' degrees were cancelled. Noteworthy Nazis, such as Max Clara taught at the university and were appointed to positions with great authority; the university was kept open throughout World War II after the destruction of its buildings. During the war the acting rector, Erich Maschke, described the continuation of the university in a memo on May 11, 1945, announcing the vote for a new rector: Since 4 December 1943 a fixed determination not to abandon the Leipzig University in the most difficult hour of its more than five-hundred-year history has bonded the professors with each other and with the students.
The special task of repairing the damage caused by air attacks has now broadened out to the more general duty to save the continuity of our university and preserve its substance, at the least its indestructible kernel, through the crisis that has now reached its fullest stage. After the destruction of most of the buildings and the majority of its libraries, this kernel is represented by the professoriate alone; this is. By the end of the war 60 per cent of the university's buildings and 70 per cent of its books had been destroyed; the university reopened after the war on February 5, 1946, but it was affected by the uniformity imposed on social institutions in the Soviet occupation zone. In 1948 the elected student council was disbanded and replaced by Free German Youth members; the chairman of the Student Council, Wolfgang Natonek, other members were arrested and imprisoned, but the university was a nucleus of resistance. Thus began the Belter group, with flyers for free elections; the head of the group, Herbert Belter, was executed in 1951 in Moscow.
The German Democratic Republic was created in 1949, in 1953 for Karl Marx Year the University was renamed by its government the Karl Marx University, Leipzig after Karl Marx. In 1968, the damaged Augusteum, including Johanneum and Albertinum and the intact Paulinerkirche, were demolished to make way for a redevelopment of the university, carried out between 1973 and 1978; the dominant building of the university was the University Tower, built between 1968 and 1972 in the form of an open book. In 1991, following the reunification of Germany, the University's name was restored to the original Leipzig University; the reconstruction of the University Library, damaged during the war and in the GDR secured, was completed in 2002. With the delivery of the University Tower to a private user, the university was forced to spread some faculties
Ernst Heinrich Weber
Ernst Heinrich Weber was a German physician, considered one of the founders of experimental psychology. He was an influential and important figure in the areas of physiology and psychology during his lifetime and beyond, his studies on sensation and touch, along with his emphasis on good experimental techniques gave way to new directions and areas of study for future psychologists and anatomists. Ernst Weber was born into an academic background, with his father serving as a professor at the University of Wittenberg. Weber became a doctor, specializing in physiology. Two of his younger brothers and Eduard, were influential in academia, both as scientists with one specializing in physics and the other in anatomy. Ernst became a lecturer and a professor at the University of Leipzig and stayed there until his retirement. Ernst Heinrich Weber was born on 24 June 1795 in Wittenberg, Holy Roman Empire, he was son to Michael Weber, a professor of theology at the University of Wittenberg. At a young age, Weber became interested in physics and the sciences after being influenced by Ernst Chladni, a physicist referred to as the “father of acoustics”.
Weber completed secondary school at Meissen and began studying medicine at the University of Wittenberg in 1811. He went on to receive his MD in 1815 from the University of Leipzig; the fighting and the aftermath of the Napoleonic wars forced Weber to relocate from Wittenberg. He became an assistant in J. C. Clarus’ medical clinic in Leipzig in 1817 and a professor in comparative anatomy in 1818 at the University of Leipzig, he became chair of human anatomy at the university in 1821. Ernst Weber’s first direct contribution to psychology came in 1834 when trying to describe the sensation of touch. Just-Noticeable Difference: Weber describes just-noticeable difference as the following, “in observing the disparity between things that are compared, we perceive not the difference between the things, but the ratio of this difference to the magnitude of things compared.” In other words, we are able to distinguish the relative difference, not the absolute difference between items. Or, we can discern between some constant ratio, not some constant difference.
Weber’s first work with jnd had to do with differences in weight, in that jnd is the "minimum amount of difference between two weights necessary to tell them apart". For this, Weber found that the finest discrimination between weights was when they differed by 8-10%. For example, if you were holding a 100g block, the second block would need to weigh at least 108g in order to notice a difference. Weber suspected that a constant fraction applied for all senses, but is different for each sense; when comparing the differences in line length, there must be at least 0.01 difference in order to distinguish the two. When comparing music pitch, there must be at least 0.006 vibrations per second difference. So for every sense, some increase in measurement is needed in order to tell a difference. Weber's Law: Weber’s Law, as labeled by Gustav Theodor Fechner, established that sensory events can be related mathematically to measurable relative changes in physical stimulus values. ΔR/R = k ΔR: amount of stimulation that needs to be added to produce a jnd R: amount of existing stimulation K: constant Weber’s law is invalid as the stimulus approaches the upper or lower limits of a sensory modality.
Fechner developed what we know today as Fechner's Law. Fechner’s Law varied and was advanced in the fact that Fechner had developed new methods for measuring just-noticeable differences in different sense modalities, making the measured results more accurate. Experimental Psychology: For most of his career, Weber worked with his brothers and Eduard, partner Gustav Theodor Fechner. Throughout these working relationships, Weber completed research on the central nervous system, auditory system and function of brain, etc. and a large portion of research on sensory physiology and psychology. The following items are part of Weber’s contributions the experimental psychology: Experimental Wave Theory: studied flow and movement of waves in liquids and elastic tubes. Hydrodynamics: applied them to circulation. In 1821, Weber launched a series of experiments on the physics of fluids in 1821 with his younger brother Wilhelm; this research was the first detailed account of hydrodynamic principles in the circulation of blood.
Weber continued his research on blood and in 1827, he made another significant finding. Weber explained the elasticity of blood vessels in the movement of blood in the aorta in a continuous flow to the capillaries and arterioles. Two-point Threshold Technique: helped map sensitivity and touch acuity on the body using compass technique. Points of a compass would be set at varying distances in order to see at what distance are the points of the compass perceived as two separate points instead of one single point. Weber wrote about and tested other ideas on sensation including a terminal threshold, the highest intensity an individual could sense before the sensation could not be detected any longer. Weber’s Illusion: an "experience of divergence of two points when stimulation is moved over insensitive areas and convergence of two points when moved over sensitive areas". Weber’s use of multivariate experiment, precise measurements, research on sensory psychology and sensory physiology laid the groundwork for accepting experimental psychology as a field and providing new ideas for fellow 19th century psychologists to expand.
In 1817, Weber was appointed as the Dozent of Psychology at Leipzig. He moved on to become
Psychophysics quantitatively investigates the relationship between physical stimuli and the sensations and perceptions they produce. Psychophysics has been described as "the scientific study of the relation between stimulus and sensation" or, more as "the analysis of perceptual processes by studying the effect on a subject's experience or behaviour of systematically varying the properties of a stimulus along one or more physical dimensions". Psychophysics refers to a general class of methods that can be applied to study a perceptual system. Modern applications rely on threshold measurement, ideal observer analysis, signal detection theory. Psychophysics has important practical applications. For example, in the study of digital signal processing, psychophysics has informed the development of models and methods of lossy compression; these models explain why humans perceive little loss of signal quality when audio and video signals are formatted using lossy compression. Many of the classical techniques and theories of psychophysics were formulated in 1860 when Gustav Theodor Fechner in Leipzig published Elemente der Psychophysik.
He coined the term "psychophysics", describing research intended to relate physical stimuli to the contents of consciousness such as sensations. As a physicist and philosopher, Fechner aimed at developing a method that relates matter to the mind, connecting the publicly observable world and a person's experienced impression of it, his ideas were inspired by experimental results on the sense of touch and light obtained in the early 1830s by the German physiologist Ernst Heinrich Weber in Leipzig, most notably those on the minimum discernible difference in intensity of stimuli of moderate strength which Weber had shown to be a constant fraction of the reference intensity, which Fechner referred to as Weber's law. From this, Fechner derived his well-known logarithmic scale, now known as Fechner scale. Weber's and Fechner's work formed one of the bases of psychology as a science, with Wilhelm Wundt founding the first laboratory for psychological research in Leipzig. Fechner's work systematised the introspectionist approach, that had to contend with the Behaviorist approach in which verbal responses are as physical as the stimuli.
During the 1930s, when psychological research in Nazi Germany came to a halt, both approaches began to be replaced by use of stimulus-response relationships as evidence for conscious or unconscious processing in the mind. Fechner's work was studied and extended by Charles S. Peirce, aided by his student Joseph Jastrow, who soon became a distinguished experimental psychologist in his own right. Peirce and Jastrow confirmed Fechner's empirical findings, but not all. In particular, a classic experiment of Peirce and Jastrow rejected Fechner's estimation of a threshold of perception of weights, as being far too high. In their experiment and Jastrow in fact invented randomized experiments: They randomly assigned volunteers to a blinded, repeated-measures design to evaluate their ability to discriminate weights. Peirce's experiment inspired other researchers in psychology and education, which developed a research tradition of randomized experiments in laboratories and specialized textbooks in the 1900s.
The Peirce–Jastrow experiments were conducted as part of Peirce's application of his pragmaticism program to human perception. Jastrow wrote the following summary: "Mr. Peirce’s courses in logic gave me my first real experience of intellectual muscle. Though I promptly took to the laboratory of psychology when, established by Stanley Hall, it was Peirce who gave me my first training in the handling of a psychological problem, at the same time stimulated my self-esteem by entrusting me fairly innocent of any laboratory habits, with a real bit of research, he borrowed the apparatus for me, which I took to my room, installed at my window, with which, when conditions of illumination were right, I took the observations. The results were published over our joint names in the Proceedings of the National Academy of Sciences; the demonstration that traces of sensory effect too slight to make any registry in consciousness could none the less influence judgment, may itself have been a persistent motive that induced me years to undertake a book on The Subconscious."
This work distinguishes observable cognitive performance from the expression of consciousness. Modern approaches to sensory perception, such as research on vision, hearing, or touch, measure what the perceiver's judgment extracts from the stimulus putting aside the question what sensations are being experienced. One leading method is based on signal detection theory, developed for cases of weak stimuli. However, the subjectivist approach persists among those in the tradition of Stanley Smith Stevens. Stevens revived the idea of a power law suggested by 19th century researchers, in contrast with Fechner's log-linear function, he advocated the assignment of numbers in ratio to the strengths of stimuli, called magnitude estimation. Stevens added techniques such as cross-modality matching, he opposed the assignment of stimulus strengths to points on a line that are labeled in order of strength. That sort of response has remained popular in applied psychophysics; such multiple-category layouts are misnamed Likert scaling after the question items used by Likert to create multi-item psychometric scales, e.g. seven phrases from "strongly