Neuroscience of music
The neuroscience of music is the scientific study of brain-based mechanisms involved in the cognitive processes underlying music. These behaviours include music listening, composing, reading and ancillary activities, it is concerned with the brain basis for musical aesthetics and musical emotion. Scientists working in this field may have training in cognitive neuroscience, neuroanatomy, music theory, computer science, other relevant fields; the cognitive neuroscience of music represents a significant branch of music psychology, is distinguished from related fields such as cognitive musicology in its reliance on direct observations of the brain and use of such techniques as functional magnetic resonance imaging, transcranial magnetic stimulation, magnetoencephalography, electroencephalography, positron emission tomography. Children who study music have shown increased development in the auditory pathway after only two years; the development could accelerate reading development. Successive parts of the tonotopically organized basilar membrane in the cochlea resonate to corresponding frequency bandwidths of incoming sound.
The hair cells in the cochlea release neurotransmitter as a result, causing action potentials down the auditory nerve. The auditory nerve leads to several layers of synapses at numerous nuclei in the auditory brainstem; these nuclei are tonotopically organized, the process of achieving this tonotopy after the cochlea is not well understood. This tonotopy is in general maintained up to primary auditory cortex in mammals, however it is found that cells in primary and non-primary auditory cortex have spatio-temporal receptive fields, rather than being responsive or phase-locking their action potentials to narrow frequency regions. A postulated mechanism for pitch processing in the early central auditory system is the phase-locking and mode-locking of action potentials to frequencies in a stimulus. Phase-locking to stimulus frequencies has been shown in the auditory nerve, the cochlear nucleus, the inferior colliculus, the auditory thalamus. By phase- and mode-locking in this way, the auditory brainstem is known to preserve a good deal of the temporal and low-passed frequency information from the original sound.
This temporal preservation is one way to argue directly for the temporal theory of pitch perception, to argue indirectly against the place theory of pitch perception. Studies suggest that individuals are capable of automatically detecting a difference or anomaly in a melody such as an out of tune pitch which does not fit with their previous music experience; this automatic processing occurs in the secondary auditory cortex. Brattico, Tervaniemi and Peretz performed one such study to determine if the detection of tones that do not fit an individual's expectations can occur automatically, they recorded event-related potentials in nonmusicians as they were presented unfamiliar melodies with either an out of tune pitch or an out of key pitch while participants were either distracted from the sounds or attending to the melody. Both conditions revealed an early frontal negativity independent of; this negativity originated in the auditory cortex, more in the supratemporal lobe with greater activity from the right hemisphere.
The negativity response was larger for pitch, out of tune than that, out of key. Ratings of musical incongruity were higher for out of tune pitch melodies than for out of key pitch. In the focused attention condition, out of key and out of tune pitches produced late parietal positivity; the findings of Brattico et al. suggest that there is automatic and rapid processing of melodic properties in the secondary auditory cortex. The findings that pitch incongruities were detected automatically in processing unfamiliar melodies, suggests that there is an automatic comparison of incoming information with long term knowledge of musical scale properties, such as culturally influenced rules of musical properties and individual expectations of how the melody should proceed; the auditory area processes the sound of the music. The auditory area is located in the temporal lobe; the temporal lobe deals with the recognition and perception of auditory stimuli and speech. The right secondary auditory cortex has finer pitch resolution than the left.
Hyde and Zatorre used functional magnetic resonance imaging in their study to test the involvement of right and left auditory cortical regions in frequency processing of melodic sequences. As well as finding superior pitch resolution in the right secondary auditory cortex, specific areas found to be involved were the planum temporale in the secondary auditory cortex, the primary auditory cortex in the medial section of Heschl's gyrus. Many neuroimaging studies have found evidence of the importance of right secondary auditory regions in aspects of musical pitch processing, such as melody. Many of these studies such as one by Patterson, Uppenkamp and Griffiths find evidence of a hierarchy of pitch processing. Patterson et al. used spectrally matched sounds which produced: no pitch, fixed pitch or melody in an fMRI study and found that all conditions activated HG and PT. Sounds with pitch activated more of these regions than sounds without; when a melody was produced activation spread to the superior temporal gyrus and planum polare.
These results support the existence of a pitch processing hierarchy. The
An optical illusion is an illusion caused by the visual system and characterized by a visual percept that appears to differ from reality. Illusions come in a wide variety. According to that, there are three main classes: physical and cognitive illusions, in each class there are four kinds: Ambiguities, distortions and fictions. A classical example for a physical distortion would be the apparent bending of a stick half immerged in water. An example for a physiological fiction is an afterimage. Three typical cognitive distortions are the Ponzo, Müller-Lyer illusion. Physical illusions are caused by e.g. by the optical properties of water. Physiological illusions arise in the eye or the visual pathway, e.g. from the effects of excessive stimulation of a specific receptor type. Cognitive visual illusions are the result of unconscious inferences and are those most known. Pathological visual illusions arise from pathological changes in the physiological visual perception mechanisms causing the aforementioned types of illusions.
A familiar phenomenon an example for a physical visual illusion are when mountains appear to be much nearer in clear weather with low humidity than they are. This is; the classical example of a physical illusion is when a stick, half immersed in water appears bent. This phenomenon has been discussed by Ptolemy and was a prototypical example for an illusion. Physiological illusions, such as the afterimages following bright lights, or adapting stimuli of excessively longer alternating patterns, are presumed to be the effects on the eyes or brain of excessive stimulation or interaction with contextual or competing stimuli of a specific type—brightness, position, size, etc; the theory is that a stimulus follows its individual dedicated neural path in the early stages of visual processing and that intense or repetitive activity in that or interaction with active adjoining channels causes a physiological imbalance that alters perception. The Hermann grid illusion and Mach bands are two illusions that are best explained using a biological approach.
Lateral inhibition, where in the receptive field of the retina light and dark receptors compete with one another to become active, has been used to explain why we see bands of increased brightness at the edge of a color difference when viewing Mach bands. Once a receptor is active, it inhibits adjacent receptors; this inhibition creates contrast. 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 been used to explain the Hermann grid illusion, but this has been disproved. More recent empirical approaches to optical illusions have had some success in explaining optical phenomena with which theories based on lateral inhibition have struggled. Cognitive illusions are assumed to arise by interaction with assumptions about the world, leading to "unconscious inferences", an idea first suggested in the 19th century by the German physicist and physician Hermann Helmholtz.
Cognitive illusions are divided into ambiguous illusions, distorting illusions, paradox illusions, or fiction illusions. Ambiguous illusions are pictures or objects that elicit a perceptual "switch" between the alternative interpretations; the Necker cube is a well-known example. Distorting or geometrical-optical illusions are characterized by distortions of size, position or curvature. A striking example is the Café wall illusion. Other examples are the famous Müller-Lyer illusion and Ponzo illusion. Paradox illusions are generated by objects that are paradoxical or impossible, such as the Penrose triangle or impossible staircase seen, for example, in M. C. Escher's Descending and Waterfall; the triangle is an illusion dependent on a cognitive misunderstanding. Fictions are when a figure is perceived though it is not in the stimulus. To make sense of the world it is necessary to organize incoming sensations into information, meaningful. Gestalt psychologists believe one way this is done is by perceiving individual sensory stimuli as a meaningful whole.
Gestalt organization can be used to explain many illusions including the rabbit–duck illusion where the image as a whole switches back and forth from being a duck being a rabbit and why in the figure–ground illusion the figure and ground are reversible. In addition, Gestalt theory can be used to explain the illusory contours in the Kanizsa's Triangle. A floating white triangle, which does not exist, is seen; the brain has a need to see familiar simple objects and has a tendency to create a "whole" image from individual elements. Gestalt means "form" or "shape" in German. However, another explanation of the Kanizsa's Triangle is based in evolutionary psychology and the fact that in order to survive it was important to see form and edges; the use of perceptual organization to create meaning out of stimuli is the principle behind other well-known illusions including impossible objects. Our brain makes sense of shapes and symbols putting them together like a jigsaw puzzle, formulating that which isn't there to that whi
Culture in music cognition
Culture in music cognition refers to the impact that a person's culture has on their music cognition, including their preferences, emotion recognition, musical memory. Musical preferences are biased toward culturally familiar musical traditions beginning in infancy, adults' classification of the emotion of a musical piece depends on both culturally specific and universal structural features. Additionally, individuals' musical memory abilities are greater for culturally familiar music than for culturally unfamiliar music; the sum of these effects makes culture a powerful influence in music cognition. Culturally bound preferences and familiarity for music begin in infancy and continue through adolescence and adulthood. People tend to remember music from their own cultural tradition. Ethnomusicologists, people who study the relationship between music and culture, never understand the music of the culture that they are studying if they spend years of their lives with that culture, they never understand.
Familiarity for culturally regular meter styles is in place for young infants of only a few months' age. The looking times of 4- to 8-month old Western infants indicate that they prefer Western meter in music, while Turkish infants of the same age prefer both Turkish and Western meters. Both groups preferred either meter when compared with arbitrary meter. In addition to influencing preference for meter, culture affects people's ability to identify music styles. Adolescents from Singapore and the UK rated familiarity and preference for excerpts of Chinese and Indian music styles. Neither group demonstrated a preference for the Indian music samples, although the Singaporean teenagers recognized them. Participants from Singapore showed higher preference for and ability to recognize the Chinese and Malay samples. An individual's musical experience may affect how they formulate preferences for music from their own culture and other cultures. American and Japanese individuals both indicated preference for Western music, but Japanese individuals were more receptive to Eastern music.
Among the participants, there was one group with little musical experience and one group that had received supplemental musical experience in their lifetimes. Although both American and Japanese participants disliked formal Eastern styles of music and preferred Western styles of music, participants with greater musical experience showed a wider range of preference responses not specific to their own culture. Bimusicalism is a phenomenon in which people well-versed and familiar with music from two different cultures exhibit dual sensitivity to both genres of music. In a study conducted with participants familiar with Western and both Western and Indian music, the bimusical participants showed no bias for either music style in recognition tasks and did not indicate that one style of music was more tense than the other. In contrast, the Western and Indian participants more recognized music from their own culture and felt the other culture's music was more tense on the whole; these results indicate that everyday exposure to music from both cultures can result in cognitive sensitivity to music styles from those cultures.
Bilingualism confers specific preferences for the language of lyrics in a song. When monolingual and bilingual sixth graders listened to the same song played in an instrumental, English, or Spanish version, ratings of preference showed that bilingual students preferred the Spanish version, while monolingual students more preferred the instrumental version. Spanish speakers identified most with the Spanish song. Thus, the language of lyrics interacts with a listener's culture and language abilities to affect preferences; the cue-redundancy model of emotion recognition in music differentiates between universal, structural auditory cues and culturally bound, learned auditory cues. Structural cues that span all musical traditions include dimensions such as pace and timbre. Fast tempo, for example, is associated with happiness, regardless of a listener's cultural background. Culture-specific cues rely on knowledge of the conventions in a particular musical tradition. Ethnomusicologist have said that there are certain situations that a certain song would be sung in different cultures.
These times are marked by the people of that culture. A particular timbre may be interpreted to reflect one emotion by Western listeners and another emotion by Eastern listeners. There could be other culturally bound cues as well, for example, rock n' roll music is identified to be a rebellious type of music associated with teenagers and the music reflects their ideals and beliefs that their culture believes. According to the cue-redundancy model, individuals exposed to music from their own cultural tradition utilize both psychophysical and culturally bound cues in identifying emotionality. Conversely, perception of intended emotion in unfamiliar music relies on universal, psychophysical properties. Japanese listeners categorize angry and happy musical excerpts from familiar traditions and unfamiliar traditions. Simple, fast melodies receive joyful ratings from these participants.
A Shepard tone, named after Roger Shepard, is a sound consisting of a superposition of sine waves separated by octaves. When played with the bass pitch of the tone moving upward or downward, it is referred to as the Shepard scale; this creates the auditory illusion of a tone that continually ascends or descends in pitch, yet which seems to get no higher or lower. Each square in the figure indicates a tone, with any set of squares in vertical alignment together making one Shepard tone; the color of each square indicates the loudness of the note, with purple being the quietest and green the loudest. Overlapping notes that play at the same time are one octave apart, each scale fades in and fades out so that hearing the beginning or end of any given scale is impossible; as a conceptual example of an ascending Shepard scale, the first tone could be an inaudible C4 and a loud C5. The next would be a louder C♯4 and a quieter C♯5; the two frequencies would be loud at the middle of the octave, the twelfth tone would be a loud B4 and an inaudible B5 with the addition of an inaudible B3.
The thirteenth tone would be the same as the first, the cycle could continue indefinitely. The acoustical illusion can be constructed by creating a series of overlapping ascending or descending scales. Similar to a barber's pole, the basic concept is shown in Figure 1; the scale as described, with discrete steps between each tone, is known as the discrete Shepard scale. The illusion is more convincing. Jean-Claude Risset subsequently created a version of the scale where the tones glide continuously, it is appropriately called the continuous Risset scale or Shepard–Risset glissando; when done the tone appears to rise continuously in pitch, yet return to its starting note. Risset has created a similar effect with rhythm in which tempo seems to increase or decrease endlessly. A sequentially played pair of Shepard tones separated by an interval of a tritone produces the tritone paradox. Shepard had predicted that the two tones would constitute a bistable figure, the auditory equivalent of the Necker cube, that could be heard ascending or descending, but never both at the same time.
In 1986, Diana Deutsch discovered the paradoxical auditory illusion where scales may be heard as either descending or ascending. Deutsch found that perception of which tone was higher depended on the absolute frequencies involved, that different listeners may perceive the same pattern as being either ascending or descending. In a film by Shepard and E. E. Zajac, a Shepard tone accompanies the ascent of an analogous Penrose stair. In his book Gödel, Bach: An Eternal Golden Braid, Douglas Hofstadter explains how Shepard scales can be used on the Canon a 2, per tonos in Bach's Musical Offering for making the modulation end in the same pitch instead of an octave higher. In Super Mario 64, a modified Shepard tone is incorporated into the music of the endless staircase, the staircase to the penultimate room in the castle. Much like a real Shepard tone, the staircase itself gives players the impression that they are running upwards, when in reality the game has locked them in place, turning around reveals that they were running in place halfway up the stairs.
In the film The Dark Knight and its follow-up The Dark Knight Rises, a Shepard tone was used to create the sound of the Batpod, a motorcycle that the filmmakers didn't want to change gear and tone abruptly but to accelerate. The Shepard tone was a key aspect in Stephin Merritt's song "Man of a Million Faces", composed for NPR's "Project Song"; the ending of the song "Echoes" from the album Meddle by Pink Floyd features a Shepard tone that fades out to a wind sound. The Austrian composer Georg Friedrich Haas uses a Shepard tone effect towards the end of his orchestral piece in vain; the song "Slow Moving Trains" from Godspeed You! Black Emperor's album F ♯. In the film Dunkirk, a Shepard tone is used to create the illusion of an increasing moment of intensity across intertwined storylines; the Shepard tone is sometimes used to build tension in electronic dance music. As the so called'build-up' in progressive dance music is a important aspect of the musical structure, the Shepard tone can be used as an effect to raise the song's energy to a certain level.
Examples of modern day dance music where a Shepard Tone has been used as rising effect are'Leave The World Behind', and'Born To Rage' The track "Endlessly Downwards" by Beatsystem from the 1995 album em:t 2295 uses a descending Shepard tone throughout its 3:25 running time. Chorus effect Flanging Interference Phaser Pitch circularity Strange loop Yadegari, Shahrokh D.. "The Shepard Tone". Self-similar Synthesis: On the Border Between Sound and Music. Archived from t
The octave illusion is an auditory illusion discovered by Diana Deutsch in 1973. It is produced when two tones that are an octave apart are played in alternation through stereo headphones; the same sequence is played to both ears simultaneously. Instead of hearing two alternating pitches, most subjects instead hear a single tone that alternates between ears while at the same time its pitch alternates between high and low; the two tones used were pitched at 400 Hz and 800 Hz, corresponding to G4 and G5 in modern pitch notation. Each tone was played for 250 ms before switching ears. No gaps were allowed between tones. Both tones were therefore always present during the experiment. After the initial test, the headphones were reversed, the test was repeated. 86 subjects were tested, none perceived the tonal pattern correctly. Most subjects heard a single tone that alternated in pitch by an octave as it alternated between ears; when the earphones were reversed, the ear that heard the high tone continued to hear the high tone, the ear that heard the low tone continued to hear the low tone.
Some subjects only heard a single tone that moved between ears but did not change in pitch, or changed slightly. Several subjects heard various "complex" illusions, such as two alternating pitches in one ear and a third pitch that sporadically occurred in the other ear. Handedness played an important role in the results. 58% of right-handed subjects and 52% of left-handed subjects heard a single pitch that switched between octaves as it switched between ears. Of the remaining subjects, nearly three times as many right-handers than left-handers heard a tone that switched ears but not pitch. Left-handed subjects were varied in their localization of the high and low tones, while right-handed subjects were much more to hear the high tone localized to their right ear during both tests. Deutsch proposed that when a single tone that alternates between octaves is heard, this illusion results from the combined operation of two decision mechanisms. First, to determine the tone's location, high pitches are given precedence.
This is known as the two-channel model, since it is proposed that the operation of two separate "what" and "where" decision mechanisms combine to produce the illusion. The model is illustrated here. In a further experiment, Deutsch examined the effect of handedness and familial handedness background on perception of the octave illusion; the subjects were 250 students, who were classified both according to their handedness and according to whether they had a left-handed parent or sibling. It was found that right-handers were more to hear the high tone on the right than were mixed-handers, mixed-handers were more to do so than left-handers, and for all three handedness groups the tendency to hear the high tone on the right was greater for subjects with only right-handed parents and siblings than for those with left- or mixed-handed parents or siblings. In another experiment and Roll explored the two-channel model in further detail, they played 44 right-handed subjects a repeating pattern of tones pitched at 800 Hz.
This time the right ear was given three 800 Hz pitches alternating with two 400 Hz pitches, while the left ear heard three 400 Hz pitches alternating with two 800 Hz pitches. A 250 ms pause was added between each successive tone combination. Subjects were asked to report how many high tones and how many low tones they heard, in which ears they heard the tones; the results were consistent with the initial experiment. In further experiments based on the same model Deutsch asked subjects to report whether the pattern was of the "high-low-high-low" type or the "low-high-low-high" type. From this it could be determined; the amplitude of the unheard pitch was manipulated in order to determine how large it needed to be, in order to counteract the effect, it was found that a significant amplitude disparity was sometimes needed. It was determined that, when both tones were not present at the same time, the illusion was broken. In yet other experiments, Deutsch varied the relative amplitudes of the high and low tones and asked subjects whether the pattern was of the "right-left-right-left-" type or the "left-right-left-right" type.
From this it could be determined whether the subject was localizing the tone to the high or low pitch. Again, it was found. Brancucci and Tommasi argue that the octave illusion should be renamed the "Deutsch illusion", according to their findings, the illusion is not limited to the octave, they performed an experiment similar to Deutsch’s original, except the two tones that were used ranged in interval from a minor third to an eleventh. The tones were presented for 200 ms before switching ears again for 500 ms. While the illusion was present for several people at all intervals, the illusion occurred more with wider intervals. Chambers and Mattingley believe that the illusion is caused by a combination of harmonic fusion and binaural diplacusis, a condition in which a pitch is perceived differently between ears. In experiments employing a few subjects, none reported the percept most obtained by Deutsch’s subjects; this does not conflict with other studies, as the number of subjec
The auditory system is the sensory system for the sense of hearing. It includes the auditory parts of the sensory system; the outer ear funnels sound vibrations to the eardrum, increasing the sound pressure in the middle frequency range. The middle-ear ossicles further amplify the vibration pressure 20 times; the base of the stapes couples vibrations into the cochlea via the oval window, which vibrates the perilymph liquid and causes the round window to bulb out as the oval window bulges in. Vestibular and tympanic ducts are filled with perilymph, the smaller cochlear duct between them is filled with endolymph, a fluid with a different ion concentration and voltage. Vestibular duct perilymph vibrations bend organ of Corti outer cells causing prestin to be released in cell tips; this causes the cells to be chemically elongated and shrunk, hair bundles to shift which, in turn, electrically affects the basilar membrane’s movement. These motors amplify the perilymph vibrations that incited them over 40-fold.
Since both motors are chemically driven they are unaffected by the newly amplified vibrations due to recuperation time. The outer hair cells are minimally innervated by spiral ganglion in slow reciprocal communicative bundles. There are 4x more OHC than IHC; the basilar membrane is a wall where the majority of the OHC sit. Basilar membrane width and stiffness corresponds to the frequencies best sensed by the IHC. At the cochlea base the Basilar is at its narrowest and most stiff, at the cochlea apex it is at its widest and least stiff; the tectorial membrane supports the remaining IHC and OHC. Tectorial membrane helps facilitate cochlear amplification by stimulating OHC and IHC. Tectorial's width and stiffness parallels Basilar's and aids in frequency differentiation; the superior olivary complex, in pons, is the first convergence of the left and right cochlear pulses. SOC has 14 described nuclei. MSO determines the angle. LSO normalizes sound levels between the ears. LSO innervates the IHC. VNTB innervate OHC.
MNTB inhibit LSO via glycine. LNTB are glycine-immune, used for fast signalling. DPO are tonotopical. DLPO are tonotopical. VLPO act in a different area. PVO, CPO, RPO, VMPO, ALPO and SPON are inhibiting nuclei; the trapezoid body is. The CN breaks into dorsal regions; the VCN has three nuclei. Bushy cells transmit their shape averages timing jitters. Stellate cells encode sound spectra by spatial neural firing rates based on auditory input strength. Octopus cells have close to the best temporal precision while firing, they decode the auditory timing code; the DCN has 2 nuclei. DCN receives info from VCN. Fusiform cells integrate information to determine spectral cues to locations. Cochlear nerve fibers each respond over a wide range of levels. Simplified, nerve fibers’ signals are transported by bushy cells to the binaural areas in the olivary complex, while signal peaks and valleys are noted by stellate cells, signal timing is extracted by octopus cells; the lateral lemniscus has three nuclei: dorsal nuclei respond best to bilateral input and have complexity tuned responses.
Ventral nuclei of lateral lemniscus help the inferior colliculus decode amplitude modulated sounds by giving both phasic and tonic responses. IC receives inputs not shown, including visual areas, spinal cord, thalamus; the above are what implicate IC in ocular reflexes. Beyond multi-sensory integration IC responds to specific amplitude modulation frequencies, allowing for the detection of pitch. IC determines time differences in binaural hearing; the medial geniculate nucleus divides into ventral and medial. The auditory cortex brings sound into awareness/perception. AC identifies sounds and identifies the sound’s origin location. AC is a topographical frequency map with bundles reacting to different harmonies and pitch. Right-hand-side AC is more sensitive to tonality, left-hand-side AC is more sensitive to minute sequential differences in sound. Rostromedial and ventrolateral prefrontal cortices are involved in activati
A barber's pole is a type of sign used by barbers to signify the place or shop where they perform their craft. The trade sign is, by a tradition dating back to the Middle Ages, a staff or pole with a helix of colored stripes; the pole may be stationary or may revolve with the aid of an electric motor. A "barber's pole" with a helical stripe is a familiar sight, is used as a secondary metaphor to describe objects in many other contexts. For example, if the shaft or tower of a lighthouse has been painted with a helical stripe as a daymark, the lighthouse could be described as having been painted in "barber's pole" colors. Borders may be marked and warnings highlighted. During medieval times, barbers performed surgery on customers, as well as tooth extractions; the original pole had a brass wash basin at the bottom. The pole itself represents the staff that the patient gripped during the procedure to encourage blood flow. At the Council of Tours in 1163, the clergy was banned from the practice of surgery.
From physicians were separated from the surgeons and barbers. The role of the barbers was defined by the College de Saint-Côme et Saint-Damien, established by Jean Pitard in Paris circa 1210, as academic surgeons of the long robe and barber surgeons of the short robe. After the formation of the United Barber Surgeon's Company in England, a statute required the barber to use a red and white pole and the surgeon to use a red pole. In France, surgeons used a red pole with a basin attached to identify their offices. Blue appears on poles in the United States as a homage to its national colors. Another, more fanciful interpretation of these barber pole colors is that red represents arterial blood, blue is symbolic of venous blood, white depicts the bandage. Prior to 1950, there were four manufacturers of barber poles in the United States. In 1950, William Marvy of St. Paul, started manufacturing barber poles. Marvy made his 50,000th barber pole in 1967, and, by 2010, over 82,000 had been produced; the William Marvy Company is now the sole manufacturer of barber poles in North America, sells only 500 per year.
In recent years, the sale of spinning barber poles has dropped since few barber shops are opening, many jurisdictions prohibit moving signs. Koken of St. Louis, manufactured barber equipment such as chairs and assorted poles in the 19th century; as early as 1905, use of the poles was reported to be "diminishing" in the United States. In Forest Grove, the "World's Tallest Barber Shop Pole" measures 72 feet; the consistent use of this symbol for advertising was analogous to an apothecary's show globe, a tobacconist's cigar store Indian and a pawn broker's three gold balls. As early as the Roman Empire, continuing through the Renaissance into Industrialization a "barber-surgeon" performed tooth extraction, leeching, enemas, etc. However, today's barber poles represent little more than being a barber shop that cuts hair and does shaves. Barber poles have become a topic of controversy in the hairstyling business. In some states, such as Michigan in March 2012, legislation has emerged proposing that barber poles should only be permitted outside barbershops, but not traditional beauty salons.
Barbers and cosmetologists have engaged in several legal battles claiming the right to use the barber pole symbol to indicate to potential customers that the business offers haircutting services. Barbers claim that they are entitled to exclusive rights to use the barber pole because of the tradition tied to the craft, whereas cosmetologists think that they are capable of cutting men's hair. In South Korea, barber's poles are used both for brothels. Brothels disguised as barbershops, referred to as 이발소 or 미용실, are more to use two poles next to each other spinning in opposite directions, though the use of a single pole for the same reason is quite common. Actual barbershops, or 미용실, are more to be hair salons. A spinning barber pole creates a visual illusion, in which the stripes appear to be traveling up or down the length of the pole, rather than around it; the Swan portion of M17, the Omega Nebula in the Sagittarius nebulosity is said to resemble a barber's pole. Barber pole-like structures have been observed at the cellular level.
The effects and causes are controversial, are subject to intense research. Matthew Walker's knot is a decorative knot. Sinosauropteryx is the first genus of non-avian dinosaur found with the fossilized impressions of feathers, as well as the first non-avian dinosaur where coloration has been determined, it was a close relative of Compsognathus. It was the first non-avialan dinosaur genus discovered from the famous Jehol Biota of Liaoning Province. Zhang found "that the filaments running down its back and tail may have made the dinosaur look like an orange-and-white-striped barber pole; such a vibrant pattern suggest that'feathers first arose as agents for color display,' Benton says." Haemo