Exam 3 Outline
Popular in Sensation and Perception
Popular in Psychlogy
This 18 page Study Guide was uploaded by Kelcie on Wednesday September 23, 2015. The Study Guide belongs to PSYC310 at University of Delaware taught by Dr. Timothy Vickery in Fall 2014. Since its upload, it has received 49 views. For similar materials see Sensation and Perception in Psychlogy at University of Delaware.
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Date Created: 09/23/15
Chapter 8 continued 11172014 Attention to Features 0 Feature search searching for a target that differs from all other items in the display 0 Regardless of items in display reaction time is similar Conjunction search searching for a target that is de ned by multiple features 0 Much more difficult 0 Response time increases as items increase oShows that binding features together requires attention to the spatial location of those features to make sure that the features are in the same location and belong to the same object The attention to spatial location affects brain activity Why Attention is Selective The binding problem problem faced by visual system of perceiving which visual features belong to the same object 0 Distributed representation representation that is distributed across multiple regions ex MT for motion and V4 for color 0 Feature integration theory FIT theory that brain solves the binding problem by selectively attending to one object and ignoring any others When attention is directed to an object neurons with an RF at attended objects location respond to that objects features only and not to the features of ignored objects Based on idea that conjunction search requires directing attention to one item at a time 0 Competition for neural representation 0 Features that match the neurons preferences drives neuron to produce a strong response while objects with features that don t match evoke only weak response l competition for neural representation competition must ne resolved or neurons response will be some sort of average or compromise that doesn t correspond to features of any of the competing objects 0 Biased competition theory theory that the brain resolves the competition for neural representation by selectively attending to one object and representing the features of just that object Directing attention to either stimulus when both presented caused neuron to respond as if only the attended stimulus was present Attentional Control 0 Attention o lnherently selective 0 Can be directed to different spatial locations and different features of perceptual objects 0 Selective attention is brains mechanism for dealing with 2 challenges to awareness of and effective cognition about the environment solving binding problem and resolving competition for neural representation 0 TopDown and BottomUp Attentional Control 0 TopDown Attentional Control voluntary attentional control deliberately paying attention to something in order to get information needed to achieve goals o BottomUp Attentional Control stimulusdriven Attentional control the involuntary unavoidable capture of attention by a salient perceptual stimulus evolved for a good reason perceptual re ex Endogenous a cue directing a person to a task in a certain spot ie Seeing another person looking in particular direction functions like a loud noise automatically directing our attention in that same direction Exogenous A cue in our peripheral eld of vision that draws our attention ie Joe had a glimpse of lynn Sources of Attentional Control in Brain 0 Signals that control attention come from 2 areas of brain posterior parietal cortex PPC and area in frontal cortex called frontal eye eld 0 Unilateral visual neglect condition in which person has difficulty attending to stimuli in one half of visual eld almost always left as a result of damage to contralateral posterior parietal cortex Awareness and the Neural Correlates of Consciousness Subjective experiences rst person data cannot be observed by others and dif cult to address scienti cally 0 Whereas quotthird person data can be found through records and calculation Neural correlates of consciousness NCCs correspondences between neural activity and conscious awareness o Idea is that if we can nd brain activity systematically correlated with conscious experience and if we can also discover what it is about that activity that makes it different from brain activity that is not correlated then we will have made progress in addressing rst person data Seeking the NCCs in perceptual Bistability o Perceptual bistability phenomenon in which an unchanging visual stimulus leads to repeated alternation between 2 different perceptual expedences Retinal image remains constant but conscious experience changes over time o Binocular rivalry phenomenon in which 2 different images presented to the 2 eyes result in perceptual bistability face and house trial 0 Damage to posterior parietal cortex can result in visual neglect failure of awareness What Blind sight Reveals about awareness 0 Blind sight ability to correctly localize and sometimes discriminate visual stimuli without any subjective experience rst person data of having seen them ability to point to and discriminate visual stimuli without conscious awareness of them 0 Residual vision in blind sight is based on signals that pass from retina to superior colliculus through thalamus and on to visual cortex Pathway cant support conscious vision but provides visual info to support visually guided action Multitasking 0 Task switching rapid shifting of attention from one task to another and back again 0 Mental gear changing 0 Can dramatically prolong time spent on each task 0 Ex Driving while talking on cell phone Sources of Sound 0 Sound is usually initiated by movement that disturbs air molecules causing them to collide with other air molecules resulting in changes in air pressure that propagate outward from the source 0 Air molecules themselves don t travel far as they oscillate back and forth but the waves of pressure changes sound waves 0 One cycle of sound change is a repeating segment of air pressure changes oSound energy decreases with distance from the source 0 Inverse square law energy decreases in proportion to the square of the distance form the source ie sounds in distance are quitter than nearby sounds Physical and Perceptual Dimensions of Sound 0 Periodic Sound Waves waves in which cycles of compression and rarefaction repeat in a regular or periodic fashion 0 Pure tone a sound wave where air pressure changes over time according to a mathematical formula sine wave Frequency is the physical dimension related to the perceptual dimension of pitch n Expressed in hertz based on the amount of cycles 1000 cycles 1000 Hz a Human range is 2020000 Hz Amplitude distance from peak to trough it is the physical dimension related to the perceptual dimension of loudness n Expressed in decibels Not micropascals because micropascals are linear where as the relationship between decibels and sound waves is logarithmic Logarithms are used because it reduces the size of the numbers that would have to be used if micropascals were the units 0 Also because as amplitude of a sound doubles the perceived loudness increases 0 The JND is 1 dB so decibels more closely expresses how changes in perceived loudness relate to changes in amplitude o 130 dB is immediate hearing loss 120 is pain threshold 0 Anything higher than 85 dB should be reduced to 8 hours or less a day Audibility Curve Absolute threshold for Hearing n Absolute threshold is the intensity of the least intense sound that can be heard but also depends on the sounds frequency a Low frequency need higher amplitudes to be heard more frequently a Audibility is most maximal in the middle range of frequencies a Yet does not account for loudness perceptual Equal Loudness Contour n Given two frequencies and need to match to the louder one n 1000 Hz at 20 dB SPL has a loudness of 20 phons whereas 1000 Hz at 10 dB SPL has a loudness of 10 phons a Our hearing is best at 5005000 Hz which is why there is a dip in the curve Aperiodic turbulent or abrupt sounds such as slamming doors 0 Fourier Analysis all complex waveforms can be broken down into a collection of sine waves with various frequencies and amplitude with a mathematical procedure o Fundamental frequency lowest frequency component of the complex waveform DETERMINES THE PERCIEVED PITCH OF THE SOUND 0 Each component is a harmonic 1st is the fundamental 2nOI is the next lowest and so on 0 Usually multiples of each other therefore if a note is A880 then 2nCI is 880 2 1760 3rd is 880 3 2640 oTwo sounds that have the same pitch same fundamental frequency and the same loudness but do not sound the same sound are said to differ in timbre due to the differences in the relative amplitudes of the various overtones Only overtones with frequencies within the range of human hearing will contribute to the timbre a Low amplitude overtones contribute to less timber than those with higher amplitude Flute vs Violin they appear to have the same pitch but they sound different because the amplitudes following the fundamental frequency is different a Removing everything but the fundamental frequency will produce a pure tone n Yet removing only the fundamental frequency will cause the pitch to stay pretty similar illusion of the missing fundamental n Timbre is also affected by its onset and offset attack and decay Piano has a rapid attack and a rapid decay loudest at rst then quickly fades o Violin is opposite Without attack and decay its hard to perceive the difference in timbre between the two instruments I Also seen in aperiodical sounds but are not associated with fundamental frequencies or harmonics The Ear 0 Outer Ear funnel sound from the environment onto the tympanic membrane which vibrates in response to the sound waves 0 Pinna outermost portion of the ear consists of fat and cartilage Shape of pinna can modify the incoming sound which contributes to soundlocaHza on oAuditory Canal funnels the sound waves onto the tympanic membrane and also ampli es frequencies in a range of 20005000 Hz which accounts for the high sensitivity to those frequencies oOuter surface of the tympanic membrane ear drum thin elastic diaphragm that forms a seal between the outer ear and the middle ear and vibrates in response to the sound waves that strike it In order for the tympanic membrane to vibrate effectively in response to incoming sound the air pressure on the outer ide of the membrane must be approximately to the air pressure on the inner side in the middle ear I Therefore when you ascend a tall building there s high pressure on the inside and low pressure on the outside and there s muf ing of sound Muf ing doesn t last due to the Eustachian tube which connects the middle ear and the top of the throat and it equalizes the air pressure 0 Middle Ear picks up vibration through ossicles and the ampli es them and then transmits them to the inner ear oOssicles three smallest bones in the entire body transmit sound energy from the tympanic membrane to the inner ear Malleus hammer lncus anvil Stapes stirrup Acoustic Re ex contraction of malleus and stapes that restricts their movement due to a high intensity sound a Which helps limit damage but only works with low frequencies and does not help with exposure to loud high frequencies I And also takes 110th of a second to occur therefore does not help during sudden noises n Besides its protective function it reduces the interferences produced by our own speech sounds and by other selfproduced noises such as coughing and chewing o In that order they then press on the oval window which is a membrane covered opening at the base of the cochlea This process exists because the cochlea is lled with uid and the sound vibrations in the air have insuf cient energy to cause signi cant vibrations in that uid I There would be a loss in sound energy 0 We make up for it by the tympanic membrane is larger than the oval window which mans that all the sound energy collected by the tympanic membrane is concentrated on a smaller area and effectively ampli es the sound 0 The physical arrangement of the ossicles produce a lever action the small action of the malleus leads to a relatively large displacement of the stapes 0 Inner Ear oCochlea within the temporal bone of the head specialized structure containing neurons that transduce the vibrations into neural signals that are then sent to the brain via the auditory nerve Vestibular canal n Reissners membrane separates the vestibular canal from the cochlear duct n Filled with perilymph Cochlear duct n Filed with endolymph a uid with electrochemical properties that facilitate auditory transduction n Basilar membrane separates the cochlear duct from the tympanic membrane a Organ of corti is located in BM which is responsible for auditory transduction 0 Inner hair cells one row 0 Pear shaped only are responsible for transducing sound into neural signals by releasing NTs 0 Connected to TYPE 1 auditory nerve bers 95 Thick and myelinated 0 Outer hair cells three rows 0 Cylindrical 0 Both contain sterocilia which protrude from the top connected to TM in OHC not IHC o Amplify and sharpen the responses of the inner hair cells 0 Depolarization of this membrane causes a change in shape of prestin and calls the stereocilia to execute physical movement like stretching and contracting motile response This causes the OHC to magnify the movements of the BM in regions with characteristic frequencies l the IHC in those regions send stronger signals in response to the sound thus amplifying sound Magni ed movements only occur in the narrow part of the BM which means that IHC sends signals that are more frequency speci c thus sharpening the response to the frequencies in sound 0 Connected to TYPE ll auditory nerve bers 5 Thin and unmyelinated 0 Tectorial membrane When the basilar membrane moves upward the sterocilia of IHC and OHC bend in the same direction 0 Tips of adjacent stereocilia are connected to one another with tiny bers tip links 0 Distance of tip links increase when sterocilia bend 0 Open channels to which they re attached with allow for potassium and calcium ions to enter and depolarize the cell membrane which leads to reactions of he IHC and OHC Auditory Nerve takes info from the hair cells to the brain Thickerstiffer part of BM are affected by highest frequencies Separates out the frequencies of the sine waves in complex waves Fourier analysis 0 How sound wave affect the basilar membrane 0 1 Pressure waves in the air sound waves cause vibration of tympanic membrane 0 2 Vibration of the tympanic membrane causes vibration of ossicles o 3 Vibration of the stapes against oval window causes pressure wave in perilymph o 4 Pressure wave in perilymph causes traveling wave in basilar membrane Tympanic canal 0 Filled with perilymph 0 Connected to the vestibular canal through helicotrema at the apex of the cochlea oSemicircular canals sense of balance of acceleration not hearing Neural Representation of Frequency and Amplitude Frequency representation is represented by the displacement of the basilar membrane at different locations with different degrees of displacement resulting in correspondingly different rates of Aps being sent along the TYPE 1 auditory bers PLACE CODE oStiffness determines its response 0 Physiological Frequency tuning curves uses direct measurement The characteristic frequency frequency that is most sensitive I Present in nerve bers just like basilar membrane 0 Their identity shows that the frequency tuning of TYPE 1 nerve bers can almost entirely be accounted for by the frequency tuning of the basilar membrane 0 As the characteristic frequency increases the more sensitive to frequency differences they are to incoming sounds o Psychophysical Frequency tuning curves based on perceptual judgments Presenter presents a target tone a pure tone with a given frequency and a low amplitude against a silent background meant to be easily detectable Then white noise with sound waves of equal amplitude narrowband white noise is presented with the target tone I The narrowband white noise is known as a masker n Masked threshold the level that just barely prevents the listener from detecting the target tone In Similar to that of the Physiological tuning curves possibly because listeners perceptual judgments are based on the responses of the TYPE 1 nerve bers 0 Also represented by a match between frequencies in the incoming sound waves and the timing of action potentials sent by TYPE 1 auditory nerve bers to the brain TEMPORAL CODE 0 O Ascending pathways Ear to Brain 0 just as in eye there are two pathways one for the right hemisphere and one for the left hemisphere 0 Type 1 auditory nerve bers carry signals from inner hair cells in the cochlea to the ipsilateral cochlear nucleus in the brain stem oSignals from the left cochlea go to the left cochlear nucleus l then the main pathways carry signals to the contralateral inferior colliculus via the tract named lateral lemniscus l contralateral medial geniculate body contralateral auditory cortex oOr signals from the left cochlea go to the left cochlear nucleus l then the main pathway pathways travel directly and indirectly via a synapse in the contralateral trapezoid body to the contralateral superior olivary complex l contralateral inferior colliculus l MGB l auditory cortex 0 But secondary pathways remain mostly on the ipsilateral side ie from the ipsilateral cochlear nucleus they travel to the ipsilateral superior olivary complex l ipsilateral inferior colliculus l some cross over to the contralateral MGB while other travel to the ipsilateral MGB l ipsilateral auditory cortex Descending Pathways Brain to Ear Are less studied than ascending pathways because in anatomical and physiological studies with animals the descending pathways are relatively inactive when the animal is under anesthesia unlike ascending pathways 0 They play a role in modulating the motile response where inhibitory neural signals from the superior olivary complex goes back to the outer hair cells 0 They are also thought to help with ear damage by activating the acoustic re ex as well as attention where they block taskirrelevant ascending auditory signals while passing task relevant ones 0 In bats it has seen that from auditory cortex l MGB may be responsible for the bats ability to discriminate similar frequencies from one another and syllables for humans Auditory Cortex found in the lateral sulcus on top of the temporal lobe Primary auditory cortex A1 is one of three areas that make up the auditory core region others are rostral core and rostrotemporal core 0 Located in the transverse temporal gyrus Heschl s gyrus oSignals from the core ow to the two regions wrapped around it the belt and parabelt o Neurons within the auditory core region are arranged into a tonotopic map where red means high and violet means low characteristic frequencies from the basilar membrane 0 Neurons with narrow tuning produced narrow responses whereas neurons with broad tuning as the amplitude increases the band became broader o Neurons with broad tuning widths might be involved in integrating component frequencies of complex sounds as part of the process of discriminating and recognizing sound sources Discrimination and recognition is carried out in the belt and parabelt similar to V4 MT and inferotemporal cortex Neurons in the belt and parabelt do not respond highly to pure tones unlike A1 and are more tuned for more complex stimuli containing multiple frequencies such as those we come across everyday life 0 What and Where pathway 0 Ventral What oSpecialized in representing the identity of sound sources extends from the ore regions into the belt and parabelt and then into the anterior parts of the temporal cortex oStoke most likely damage to ventral Dorsal quotWherehow oSpecialized for representing the location of sound sources extends from the core regions into posterior parts of the auditory cortex and eventually into the posterior parietal cortex Localizing Sound 0 There is NOT corresponding explicit representation of location the cochlea is organized tonotopically where it represents frequency not location 0 Instead the auditory system evolved a system based on comparing aspects of the sound arriving at the two ears Perceiving Azimuth the side to side dimension oCan be quanti ed psychophysically constant stimuli For example place a person in the middle of a circle surrounded by closely spaced speakers then a pure tone is emitted by one of the speakers and then followed by another tone that has the same frequency is emitted from another speaker then the listener must decided whether the second tone was left or right to the pure tone reference tone When the angle between the tones is large the listener is almost always correct whereas a smaller angle the listener begins to make errors Minimum audible angle the minimum angular separating between two different speakers that yields 75 correct judgments n Smaller the MAA more accurate the listener is o lnteraural Level Differences difference in sound level in two ears or quotD When a sound is equally close to both ears it is equally intense in both ears when it is closer to one ear it is more intense in that ear I Intensity of sound decreases with distance from the sources according to the inverse square law a The head processes an acoustic shadow where the head partially blocks the sound waves traveling to the far ear 0 Has a much greater affect on high frequency sounds than low frequency sounds lLD increases steadily from 0 degrees to 90 degrees azimuth and decreases from 180 degrees to 0 Much easier to detect a large B than a smaller one o lnteraural Time Differences difference in arrival times If the time between sounds is brief enough the listener perceives a single tone and is determined coming from the left or the right according to which ear heard the rst sound Most people have an ITD threshold of 100 us or less 0 when directly ahead or behind head 0 or 180 azimuth oCone of Confusion hypothetical cone shaped surface in auditory space when two equally distant sound sources are located on a cone of confusion their locations are confusable because they have highly similar lLD and ITD Solved through head movement as soon as you turn your head to one side the lLD and ITD of the sound change in a way that instantly disambiguates the azimuth of the source 0 Perceiving Elevation the updown dimension 0 Pinna allows humans to judge elevation in domestic cats they can move their pinnae accordingly 0 Pinnae contain bumps and ridges as incoming sound waves are funneled by the pinna into the auditory canal they re ect off the bumps and ridges and reverberate slightly which ampli es some frequencies and attenuates others changing the shape of the frequency spectrum oSpectral Shape Cue pinna induced modi cation of the spectrum that provides information about the elevation of the sound source Each persons pinnae are unique so the spectral shape cues produced by your own particular pinnae needs to be learned Experiment a person wears an arti cial pinnae with a different pattern of bumps and ridges from the persons natural pinnae the persons elevation judgment is greatly impaired when rst using the arti cial pinnae but improves with time This cue works best for broadband sounds sounds with wide range of frequencies as opposed to pure tones a People are pretty poor at judging the elevation of pure tones o Perceiving Distance distance of the center of the head in any direction 0 If the proportion is more direct than re ected it is near and if the proportion is more re ected than direct it is far 0 Loudness cue as a sound source approaches a listener the loudness increases 0 Echo can also be used when there are hard surfaces to re ect sound waves 0 Doppler Effect the frequency of a sound emitted by a moving sound source is higher in front of the sound source than behind it train cars zipping by ambulance Echolocation by Bats and Humans o Echolocation emitting a sequence of high frequency sounds in the range of 20000 to 100000 Hz and then processing the echoes to determine whether the sound was re ected and then eventually move in on the object o Incorporates azimuth distance and elevation as wells as the information about the size and shape of object and the physical characteristics of the targets surface such as hardness or texture oWhen blind people were compared to people with sight those with sight bumped into the wall more and could sense the wall when they were only a meter or less away When wearing earplugs both blinded and sight people were unable to detect the wall and collided every time 0 Neural Basis of Sound Localization Medial Superior olivary MSO part of the superior olivary complex in the brain stem is thought to contain neurons that function as a mechanism for detecting lTDs and representing the azimuths of sound sources 0 Neurons in both the left and right MSO receive signals from both the left and right cochlear nuclei and are considered coincidence detectors they only re if the signal from the two cochlear nuclei arrive a the same time Neurons are tuned for speci c ITD and if that certain ITD occurs the one that is tuned for it will respond strongly while the others will not be as strong Neurons in the brain are also tuned for different lLDs and the responses provide a neural code for sound localization using lLDs Auditory Scene Analysis extracting the frequencies associated with each of the sound sources in a scene Auditory scene combination of sound waves from different sources friend talking alarm going off o Auditory stream assortment of frequencies occurring over time that all quotgo togetherquot because they ere emitted by the same sound source or by related sources 0 Le frequency of your friends voice distinct from the alarm going off Simultaneous Grouping o Harmonic Grouping frequencies that are harmonics integer multiples of the same fundamental frequency tend to be grouped together as part of the same auditory system When presented with harmonics the auditory system analyzes two possibilities I That all harmonics are coming from a single source more likely a Many independent sources are emitting frequencies that completely by chance are related to each other in precisely this way oSynchrony frequencies that begin end or change at the same time also tend to be grouped together ie auditory scene begins in silence and the several frequency components appear simultaneously Similar to common motion Asynchrony when it does not match up Sequential Grouping group frequencies that occur at different times oGrouping by Frequency Similarity When a listener hears a sequence of pure tones that vary between two frequencies and the alternating frequencies are close to one another then the listener often perceives the sequences as a single auditory stream Flanker tones make it hard to distinguish tones without anker tones its easy Captor tones quotcapturequot the anker tones and make them both perceived as a sequences of tones similar frequency and are distinct from the others oTemporal Proximity Shorter distance between two different frequencies shows that they re different tones But if there is a long time between the two frequencies that are considered one stream Occluded Sounds 0 Long occluded sounds unable to perceive what is said Short occluded sounds might not even noticed it happen and will be able to perceive A person will assume that the sound went on anyways and the occluding sound disrupted it small spurts of occlusion verse being separated by silent gaps oSimilar to visual interpolation Seeing by Hearing Sensory substitution when one sense is used to determine something that is usually meant to be determined by another sense oSensory Substitution Device arti cial aid used in this process 0 Phonemes smallest nits of sound that if changed would change the meaning of a word 0 Cap to cat to sat to saw 0 International Phonetic Alphabet IPA each symbol stands for a different speech sound Producing Speech 0 Exhalation of air from the lungs I 0 Air ows through the trachea l 0 Into larynx voice box air then passes through a pair of membranes named vocal folds still in larynx vocal cords l o Folds can be relaxed and open allowing air to pass silently or tense which causes them to vibrate as air passes which causes higher pitch oThe vocal fold vibration depends on size and shape of larynx as well as the current degree of contraction or relaxation of muscle in the throat Females have higher fundamental frequencies than men and kids have the biggest overall 0 Pharynx upper part of throat l oral and nasal cavities I exits body via mouth or nose 0 Uvula ap of tissue that hangs off the posterior edge of the soft palate can bend upward to close off the nasal cavity directing all exhaled air into oral cavity and out of the mouth Important in pronouncing some speech sound Vowels are produced with a relatively unrestricted blood ow of air through the pharynx and the oral cavity 0 Frequency spectrum of vowels are constant over time oWith different vowels depending on size and shape of oral cavity because different shapes have different resonances and resonance determines frequency and how much Open jaw to different angle Formants frequency bands with relatively high amplitude in the spectrum of a vowel sound most vowels contain two or more a Are what are separated out by the ltering function due to the shape of the oral cavity underneath curve Consonants are produced by restricting the ow of air at one place or another along the path of air ow from the vocal folds oCan be de ned in three terms Place of articulation describes the point at which this restriction occurs and the anatomical structures involved in creating restriction Manner of articulation describes the nature of restriction Voicing speci es whether the vocal folds are vibrating or not whether sound is voiced or not Lips teeth tongue palate and velum are used to create the restriction involved in producing consonants Speech Perception o The task of analyzing the stream of speech into phonemes is actually challenging because here is not one to one correspondence between the sounds produced by talkers and the phonemes that those sounds represent 0 Many acoustic events may represent the same phoneme 0 Lack of one to one correspondence can be due to different talkers producing sounds with different fundamental frequencies oAlso the sounds of speci c phonemes differ in different dialects ie many vowel sounds are pronounced quite differently when comparing NY and TX yet there would be little trouble understanding them oAnother is the indistinct boundaries between words What will you give me for leaving Or Whaddllya gimme ferlea vin Not so many silences and phonemes are missing or modi ed Having knowledge of language and using in context help Auditory system using relative positions of frequencies such as formants in vowel sounds in the context of the entire speech stream as well as other patterns of acoustic features to identify the phonemes in speech Coarticulation and Perceptual Constancy oCoarticulation the in uence of one phoneme on the acoustic properties of another due to the articulatory movements require to produce them in a sequence Consonant and vowel productions overlap in time It not only affects the ow across the transition from one phoneme to the next but also ow backward from an upcoming phoneme to the phoneme currently being produced Due to coarticulation a given sound is regularly associated with different acoustic features like the frequencies transitioning to the second formant of the following vowel du vs dee o Categorical Perception the perception of different sensory stimuli as identical up to a point at which further variation in the stimulus leads to sharp change in the perception oWhereas continues perception there is no sharp changes when the stimulus vanes oVOT voice onset time the interval between the initial burst of frequencies corresponding to the consonant and the onset of the following vowel Are usually relatively long for voiceless and relatively short for voiced Experiment experimenters create synthetic stop consonants that are identical except for the differences in VOT Then they combined those sounds into syllables with synthetic vowel sounds and asked listeners to decide whether each syllable sounded like It began with a voiceless without vibration or voiced with vibration stop I Phonemic boundary the VOT at which a stop consonant transitions from being mainly perceived as voiced to being mainly perceived as voiceless n The reasoning of this could be due to the idea there are quotdetectorsquot in the auditory system tuned to respond to certain ranges of VOTs o McGurk Effect in the perception of speech sounds when auditory and visual stimuli con ict the auditory system tends to compromise on a perception that s hares features with both the seen and the hear stimuli if no good compromise perception is available either the con ict is resolved in favor of the visual stimulus or there is a con icting perceptual experience oWhen someone says baba with their mouth but you hear gag a listeners either perceive b aba ba gba or ga bass 0 Knowledge and Speech Perception 0 Knowledge of the probability of various sequences of phonemes within words or across words in the language they re hearing brf is not a word so if you heard it you might assume it was bluff oKnowledge of the context in which an utterance is being produced Hearing brf and knowing that the speaker is talking about her dog and that dogs name is duff and consciously or subconsciously perceive duff oWord Segmentation One way we make words distinct could be by guessing a new word has started when they hear a sound that is unlikely to be part of the same word as the preceding sound Phoneme transition probabilities for any particular sequence of phonemes the chances that the sequence occurs at the start of a word in the middle of a word at the end of a word or across the boundary between two words a Not the only thing you can rely on oPhonemic Restoration a kind of perceptual completion in which listeners seem to perceive obscured or missing speech sounds Sentence is interrupted by something but you can still ll it in Listeners could not accurately say which part of the sentence was masked when a sound interrupted the sentence and claimed nothing was masked Yet when there was silence instead of the sound they could accurately Music 0 Pitch most fundamental dimension of music the single characteristic that most clearly distinguishes one musical composition from another Octave a sequence of notes in which the fundamental frequency of the last note is double the fundamental frequency of the rst note A4 on piano is 220 Hz A5 is 440 Hz and so forth 0 Each octave contains 13 notes separated by 12 proportionally equivalent intervals called semitones oC4 is more similar to C5 than B4 because harmonics of the notes played by a musical instrument are integer multiples of the fundamental frequency oThe difference in adjacent keys the pitch seems to be constant but actually the frequency in different and there is a large difference as you move up Melody tune a sequence of musical notes arranged in particular rhythmic pattern which listeners perceive as a single recognizable unit oThe most important aspect of a melody is the relative positions of the pitches in the sequence not the absolute pitch Over the rainbow can start with any key as long as it continues in the same intervals the sequence will be perceived as the melody Transposition containing the same intervals but starting at different notes Consonance the quality exhibited by a combination of two or more notes from a scale that sounds pleasant as if the note go together Dissonance the quality exhibited by a combination of two ore more noes fro ma scale that sounds unpleasant or quotoffquot 0 Important to understand the degree to which the harmonics of the notes in combination coincide harmonicity oMore harmonicity more consonant Neural Basis of Music Perception Left hemisphere is more active than the right hemisphere in processing speech and its been suggested that left auditory cortex is specialized for representing the ne differences in timing that are crucial in speech perception Left part of brain responds equal to xed pitch and changing pitch whereas right only respond to xed pitched sequences 0 Less that one percent of the population have the ability known as absolute pitch they can listen to isolated notes and name them accurately and name isolated colors 0 For impairments about 4 percent of the population cannot remember melodies or distinguish one melody from another but are normal in perceiving speech amu a 0 When comparing musicians and nonmuscians listening to music they had the same pattern of activity but the magnitude was signi cantly greater in the musicians O 0 Rubber band illusion lf visual and tactile information is applied synchronously then people may feel that the touches on their own hand are coming from the dummy hand 0 Even that the dummy hand is in some way their own hand 0 an illusion of vision touch and proprioception posture Body Senses 0 Skin deformation tactile perception touch 0 Muscle stretch and joint angle for monitoring limb position and movement proprioception Pain for detecting actual or potential tissue damage nociception 0 Temperature of something contracting the skin thermoreception Object shape perceived through touch and proprioception together haptics Balance and acceleration of the body Tactile Perception touch is perception that results form the mechanical deformation indentation vibration or stretching of the skin 0 Skin is divided into two forms hairy skin and skin without hair glabrous skin and has two main layers epidermis and the dermis Located mainly within the dermis there are sensory receptors known as mechanoreceptors which transduce mechanical deformations of the skin into neural signals that are sent to the brain oSow adapting SA mechanoreceptors are SA1 mechanoreceptors and SAN mechanoreceptors They produce a burst of action potentials at the onset of skin deformation but then a lower sustained response until the stimulus is removed from the skin 0 Fast Acting FA mechanoreceptors are FAl mechanoreceptor and FA mechanoreceptors They produce a burst of action potentials only at the onset and offset of skin deformation FA are sensitive to abrupt changes in stimulation which makes them well suited for detecting vibration and motion oAdapting is used in both cases to show that sensory bers tend to reduce their ring rate during prolonged unchanging stimulation from an initial high level to either a lower sustained level SA or to zero FA oSAl and FAl have relatively small receptive elds and are densely arranged near the surface of the skin which ves them a high spatial resolution 0
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