Chapter 11Chapter 11

Hearing and ListeningHearing and Listening

Prenatal hearingPrenatal hearing

Babies can hear in utero.Babies can hear in utero. Mother’s heartbeat, breathing, speaking, Mother’s heartbeat, breathing, speaking,

singing, and stomach gurgles.singing, and stomach gurgles. Baby learns to identify mother’s voice in utero.Baby learns to identify mother’s voice in utero. Hard to measure human auditory capacity.Hard to measure human auditory capacity. This includes numerous voices, as well as This includes numerous voices, as well as

everyday sounds, such as walking, laughing, everyday sounds, such as walking, laughing, crying, hammering, …crying, hammering, …

Sound enables us to judge shape of struck Sound enables us to judge shape of struck objects, quantity of fluid in a vessel, loose objects, quantity of fluid in a vessel, loose screws.screws.

Can sort a single sound source from Can sort a single sound source from background, e.g. a person’s voice in a crowded background, e.g. a person’s voice in a crowded stadium.stadium.

Range and limits of hearingRange and limits of hearing

Threshold intensity = the softest sound that Threshold intensity = the softest sound that can be hear (at a given frequency).can be hear (at a given frequency).

A plot of threshold intensity versus frequency A plot of threshold intensity versus frequency yields an audibility function.yields an audibility function.

Reference frequenciesReference frequencies

Lowest note on a piano: 27.5 HzLowest note on a piano: 27.5 Hz Middle C: 261.63 HzMiddle C: 261.63 Hz Highest note on a piano: 4,186 HzHighest note on a piano: 4,186 Hz Typical phone: 4,000-8,000 HzTypical phone: 4,000-8,000 Hz TV whine: 16,000 HzTV whine: 16,000 Hz

Hearing lossHearing loss

In the U.S., ~28 million suffer some form of In the U.S., ~28 million suffer some form of hearing loss.hearing loss.

(Cf., ~10 million suffer age-related macular (Cf., ~10 million suffer age-related macular degeneration)degeneration)

Total Deafness = Cannot hear voices at less tht Total Deafness = Cannot hear voices at less tht 82 dB.82 dB.

Auditory impairment = substandard audibility Auditory impairment = substandard audibility function.function.

Two types of hearing lossTwo types of hearing loss

Conduction: Due to problems in the outer and Conduction: Due to problems in the outer and middle ear.middle ear.

Sensory/neural: Due to problems in the inner Sensory/neural: Due to problems in the inner ear and brain.ear and brain.

Conduction lossesConduction losses

Excessive ear wax.Excessive ear wax. Middle ear infectionsMiddle ear infections

Persistent infections in infants can lead to permanent Persistent infections in infants can lead to permanent sensory deficits, since the brain is still developing.sensory deficits, since the brain is still developing.

Otosclerosis: Immobilization of stapes by buildup of Otosclerosis: Immobilization of stapes by buildup of spongy substance.spongy substance. Progressive conditionProgressive condition Tends to occur in young adults.Tends to occur in young adults. More frequent in females than males.More frequent in females than males. Treated surgically.Treated surgically.

Sensory/neural lossesSensory/neural losses Presbycusis: Age related loss of high frequency sensitivity. Presbycusis: Age related loss of high frequency sensitivity.

Perhaps unavoidable.Perhaps unavoidable. 30 years: lose > 15,000 Hz30 years: lose > 15,000 Hz 50 years: lose > 12,000 Hz50 years: lose > 12,000 Hz

For all ages, men tend to have greater hearing loss than For all ages, men tend to have greater hearing loss than women.women.

Perhaps due to changes in basilar membrane.Perhaps due to changes in basilar membrane. Perhaps due to changes in vasculature.Perhaps due to changes in vasculature. Perhaps due to cumulative exposure to loud noises.Perhaps due to cumulative exposure to loud noises.

Supported by reduced hearing loss in African tribal populations.Supported by reduced hearing loss in African tribal populations.

Noise exposure and hearing lossNoise exposure and hearing loss

Single explosive events can lead to hearing Single explosive events can lead to hearing loss, e.g. guns.loss, e.g. guns.

Sustained loud noise, as in music or factoriesSustained loud noise, as in music or factories May be as high as 60% among teens in U.S.May be as high as 60% among teens in U.S. At all frequencies, those who regularly attend rock At all frequencies, those who regularly attend rock

concerts have higher auditory thresholds.concerts have higher auditory thresholds.

Short exposures to loud noises (> ~60dB) lead Short exposures to loud noises (> ~60dB) lead to to temporary threshold shiftstemporary threshold shifts.. Such short exposures can occur when using Such short exposures can occur when using

household appliances.household appliances.

Women tend to have lower threshold shifts Women tend to have lower threshold shifts than men when low frequencies are inducersthan men when low frequencies are inducers

Men tend to have lower threshold shifts than Men tend to have lower threshold shifts than women when high frequencies are inducers.women when high frequencies are inducers.

Drugs and hearing lossDrugs and hearing loss

Nicotine users have higher high-frequency Nicotine users have higher high-frequency thresholds than non-users.thresholds than non-users. May be due to changes in circulation, which May be due to changes in circulation, which

deprive cochlea.deprive cochlea. Aspirin also produces temporary hearing loss.Aspirin also produces temporary hearing loss.

The dosage for this is about what is recommended The dosage for this is about what is recommended for handling rheumatoid arthritis.for handling rheumatoid arthritis.

Aspirin also makes one more susceptible to the Aspirin also makes one more susceptible to the effects of noise.effects of noise.

Compensating for hearing lossCompensating for hearing loss

Hearing aidsHearing aids Amplify incoming sounds by up to 60dB.Amplify incoming sounds by up to 60dB. They tend to favor sounds for speech, i.e. 250-They tend to favor sounds for speech, i.e. 250-

4,000Hz.4,000Hz.

Compensating for hearing lossCompensating for hearing loss

Cochlear implantsCochlear implants Help if only cochlea is damaged; loss of auditory nerve or Help if only cochlea is damaged; loss of auditory nerve or

auditory cortex cannot be helped.auditory cortex cannot be helped. Sounds are transformed into electrical stimulation of the Sounds are transformed into electrical stimulation of the

auditory nerve.auditory nerve. Do not produce normal hearing, but only responsiveness to Do not produce normal hearing, but only responsiveness to

sound.sound. ~100,000 people worldwide have cochlear implants. Half ~100,000 people worldwide have cochlear implants. Half

are children; half adults.are children; half adults. ~30,000 in U.S. (?)~30,000 in U.S. (?) May work best when implanted early.May work best when implanted early.

Cochlear implantsCochlear implants

A prime candidate for cochlear implants is described as:A prime candidate for cochlear implants is described as: having severe to profound having severe to profound sensorineuralsensorineural hearing impairment hearing impairment in both ears in both ears a functioning auditory nerve is present a functioning auditory nerve is present has lived a short amount of time without hearing has lived a short amount of time without hearing has good speech, language, and communication skills, or in the case of has good speech, language, and communication skills, or in the case of

infants and young children, has a family willing to work toward speech and infants and young children, has a family willing to work toward speech and language skills with therapy language skills with therapy

other kinds of hearing aids are not helping other kinds of hearing aids are not helping no medical reason to avoid surgery no medical reason to avoid surgery lives in or desires to live in the "hearing world" lives in or desires to live in the "hearing world" has realistic expectations about results has realistic expectations about results has the support of family and friends. has the support of family and friends.

Hearing in non-human animalsHearing in non-human animals

Noise masking and critical bandsNoise masking and critical bands

Auditory masking = not hearing in the Auditory masking = not hearing in the presence of ambient noise, e.g. shower or presence of ambient noise, e.g. shower or traffic.traffic.

dB masked – dB unmaskeddB masked – dB unmasked

Broad band noise versus bandpass noiseBroad band noise versus bandpass noise

Noise masking and critical bandsNoise masking and critical bands

After a certain point, further increases in noise After a certain point, further increases in noise bandwidth does no more masking.bandwidth does no more masking.

The noise bandwidth at which this occurs The noise bandwidth at which this occurs defines the critical band.defines the critical band.

The inflection point is the frequency limit The inflection point is the frequency limit (tuning width) of the fiber.(tuning width) of the fiber.

Variations in masking paradigmVariations in masking paradigm

Varying width of noise of fixed intensityVarying width of noise of fixed intensity Varying position of noise of fixed intensityVarying position of noise of fixed intensity Removing center frequencies (notched Removing center frequencies (notched

spectrum)spectrum) Varying intensity of noise of fixed bandwidth Varying intensity of noise of fixed bandwidth

and position.and position.

Noise maskingNoise masking

Bottom line: Noise only masks when it is near Bottom line: Noise only masks when it is near the test frequencythe test frequency

Loudness perception and Loudness perception and discriminationdiscrimination

Loudness perception can be measured by Loudness perception can be measured by matching a variable tone to a target tone.matching a variable tone to a target tone.

Loudness perception can also be measured by Loudness perception can also be measured by assigning a number to the perceived loudness.assigning a number to the perceived loudness.

Loudness perceptionLoudness perception

Loudness depends on frequency: Equal Loudness depends on frequency: Equal loudness contours.loudness contours.

Lower frequencies tend to sound weaker, Lower frequencies tend to sound weaker, which is why audio manufacturers add which is why audio manufacturers add mechanisms to increase their strength.mechanisms to increase their strength.

How does perceived loudness vary How does perceived loudness vary with sound intensity?with sound intensity?

Perceived loudness is a logarithmic function of Perceived loudness is a logarithmic function of intensityintensity

Neural bases of loudness perceptionNeural bases of loudness perception

Partially auditory neuron firing rates.Partially auditory neuron firing rates. A given neuron can vary firing rate over about A given neuron can vary firing rate over about

40dB, but normal humans can hear loudness 40dB, but normal humans can hear loudness variations over 130dB.variations over 130dB.

Partially different neurons respond to different Partially different neurons respond to different sound intensities.sound intensities. 20-60 dB, 40-80dB, and 60-100 dB.20-60 dB, 40-80dB, and 60-100 dB.

Partially due to more intense sounds activating Partially due to more intense sounds activating more neurons outside their tuning frequencies.more neurons outside their tuning frequencies.

Loudness discriminationLoudness discrimination

Discrimination threshold is the least Discrimination threshold is the least perceptible change.perceptible change.

For loudness, the discrimination threshold is For loudness, the discrimination threshold is ~1-2dB, though it depends on details of ~1-2dB, though it depends on details of experimental measuring procedure, etc.experimental measuring procedure, etc.

Loudness discriminationLoudness discrimination

““Traditional” view: Discrimination of pure Traditional” view: Discrimination of pure tones depends on changes in the frequency of tones depends on changes in the frequency of firing of the neurons tuned to that frequency.firing of the neurons tuned to that frequency.

Profile analysis: Discrimination of tones Profile analysis: Discrimination of tones depends on comparing changes in a few depends on comparing changes in a few frequencies against a backdrop of other frequencies against a backdrop of other frequencies.frequencies.

Experiment 1: Experiment 1: Subjects compared pairs of stimuli.Subjects compared pairs of stimuli. Stimuli = combinations of 21 different tones Stimuli = combinations of 21 different tones

300-3,000Hz in frequency300-3,000Hz in frequency In one of the pair, all 21 tones had the same In one of the pair, all 21 tones had the same

intensity. intensity. In the other of the pair, one of the 21 tones In the other of the pair, one of the 21 tones

increased in intensity.increased in intensity.

David Green, (1982)David Green, (1982)

Experiment 1 results:Experiment 1 results: Subjects were almost as good in identifying Subjects were almost as good in identifying

the changed tone against the backdrop of 20 the changed tone against the backdrop of 20 other tones as they were in identifying the other tones as they were in identifying the changed tone in isolation.changed tone in isolation.

David Green, (1982)David Green, (1982)

Experiment 2:Experiment 2: Subjects compared pairs of stimuli.Subjects compared pairs of stimuli. Stimuli = combinations of different tones 300-Stimuli = combinations of different tones 300-

3,000Hz in frequency3,000Hz in frequency In one of the pair, all tones had the same intensity. In one of the pair, all tones had the same intensity. In the other of the pair, one of the tones increased in In the other of the pair, one of the tones increased in

intensity.intensity. Green varied the number of tones in each of the Green varied the number of tones in each of the

stimuli.stimuli.

David Green, (1982)David Green, (1982)

Experiment 2 results:Experiment 2 results: Subjects could make finer loudness Subjects could make finer loudness

discriminations with more tones, i.e., the more discriminations with more tones, i.e., the more complex background helped make differences complex background helped make differences more detectable.more detectable.

Pitch Pitch ≠ frequency≠ frequency

Pitch is a psychological property; frequency is a Pitch is a psychological property; frequency is a physical property of sound waves.physical property of sound waves.

Loudness influences pitch:Loudness influences pitch: At 300Hz, louder is lower.At 300Hz, louder is lower. At 3,000 Hz, louder is higher.At 3,000 Hz, louder is higher.

Background tones influence pitchBackground tones influence pitch Lower background tones make a tone’s pitch higher.Lower background tones make a tone’s pitch higher. Higher background tones make a tone’s pitch lower.Higher background tones make a tone’s pitch lower.

The Missing FundamentalThe Missing Fundamental

The lowest frequency of a tone is its The lowest frequency of a tone is its fundamental frequency. (Blake & Sekuler’s fundamental frequency. (Blake & Sekuler’s text is less than maximally clear on this; cf. the text is less than maximally clear on this; cf. the glossary.)glossary.)

Theoretically, a fundamental frequency gives Theoretically, a fundamental frequency gives rise to integer multiples of this frequency. rise to integer multiples of this frequency. This multiples are the “harmonics.”This multiples are the “harmonics.”

The Missing FundamentalThe Missing Fundamental

Synthesize the patterns only without the Synthesize the patterns only without the fundamental and the tone sounds like the fundamental and the tone sounds like the original.original.

Harmonics produce timbreHarmonics produce timbre Pure tones and musical notes produce Pure tones and musical notes produce tonal tonal

pitch.pitch. Complex aperiodic notes produce Complex aperiodic notes produce atonal pitchatonal pitch..

Neural basis of pitch perceptionNeural basis of pitch perception

Perhaps pitch is based on the activity of neurons Perhaps pitch is based on the activity of neurons corresponding to the fundamental frequency. corresponding to the fundamental frequency. (Place theory)(Place theory)

Supporting evidence:Supporting evidence: Damage to a region of the basilar membrane Damage to a region of the basilar membrane

causes losses of specific frequency sounds.causes losses of specific frequency sounds. Cochlear implants can replace specific frequencies.Cochlear implants can replace specific frequencies.

Neural basis of pitch perceptionNeural basis of pitch perception

Evidence contrary to Place Theory:Evidence contrary to Place Theory: Frequencies below 1,000 Hz do not register in any Frequencies below 1,000 Hz do not register in any

specific place on the basilar membrane, yet such specific place on the basilar membrane, yet such tones are easily identified.tones are easily identified.

Time delayed tones.Time delayed tones.

Neural basis of pitch perceptionNeural basis of pitch perception

Temporal theory: Pitches correspond to firing Temporal theory: Pitches correspond to firing rates of neurons.rates of neurons. This is observed in some neurons.This is observed in some neurons.

Together place theory and temporal theory Together place theory and temporal theory explain pitch perception.explain pitch perception.

Sound RecognitionSound Recognition

How do we separate the sound produced by a How do we separate the sound produced by a single object from background noise, when all single object from background noise, when all the sound waves are present at once?the sound waves are present at once?

In other words, how do we form In other words, how do we form auditory auditory imagesimages??

Sound recognitionSound recognition

Common spectral contentCommon spectral content Common time courseCommon time course Spectral HarmonicsSpectral Harmonics FamiliarityFamiliarity LocalizationLocalization

Grouping by common spectral Grouping by common spectral contentcontent

Bregman (1990) experiment 1Bregman (1990) experiment 1 Played a tune “Mary had a little lamb.” Played a tune “Mary had a little lamb.” Between the notes, he added noise of similar frequencies.Between the notes, he added noise of similar frequencies. This blocked hearing of the tune.This blocked hearing of the tune.

Bregman (1990) experiment 2Bregman (1990) experiment 2 Played a tune “Mary had a little lamb.” Played a tune “Mary had a little lamb.” Between the notes, he added noise of higher frequencies.Between the notes, he added noise of higher frequencies. This did not block hearing of the tune.This did not block hearing of the tune.

Recall Gestalt principle of grouping by similarity.Recall Gestalt principle of grouping by similarity.

Spectral contentSpectral content

Cannot be the whole story, since two women’s Cannot be the whole story, since two women’s voices have similar spectral content, but are voices have similar spectral content, but are still easily discerned.still easily discerned.

Common time courseCommon time course

Form an image by grouping together the frequencies Form an image by grouping together the frequencies that temporally vary together.that temporally vary together.

This can be observed by using sound recordings in This can be observed by using sound recordings in which some frequencies are artificially delayed which some frequencies are artificially delayed relative to others.relative to others.

This, too, cannot be the whole story, since voices This, too, cannot be the whole story, since voices singing in unison can clearly be discriminated.singing in unison can clearly be discriminated.

Spectral harmonicsSpectral harmonics

Frequencies that are multiples of each other Frequencies that are multiples of each other tend to be heard together, e.g. a sound tend to be heard together, e.g. a sound involving frequencies of 440, 880, and 1,320 involving frequencies of 440, 880, and 1,320 Hz tend to go together.Hz tend to go together.

FamiliarityFamiliarity

One can overcome background noise with One can overcome background noise with familiarity or priming.familiarity or priming.

Practice can do this in Bregman’s (1990) Practice can do this in Bregman’s (1990) paradigm.paradigm.

FamiliarityFamiliarity

It is easier for you to separate voices of It is easier for you to separate voices of English than of, say, Japanese.English than of, say, Japanese.

Variations in musical chords (tones) are more Variations in musical chords (tones) are more readily discerned than variations in non-readily discerned than variations in non-musical combinations of tones.musical combinations of tones.

Sounds localizationSounds localization

The direction of a sound is not an intrinsic The direction of a sound is not an intrinsic feature of the acoustic signal. feature of the acoustic signal.

In this regard, sound localization differs from In this regard, sound localization differs from visual localization.visual localization.

IID and ITDIID and ITD

Stevens & Newman, (1934).Stevens & Newman, (1934). Person seated on a roof with speaker at the end of an arm Person seated on a roof with speaker at the end of an arm

with constant elevation relative to listener.with constant elevation relative to listener.

<1,000 Hz localization was good<1,000 Hz localization was good 2,000 – 4,000 Hz localization was less good2,000 – 4,000 Hz localization was less good > 4,000 Hz localization improved> 4,000 Hz localization improved

Duplex theory of localization:Duplex theory of localization: Low frequencies depend on ITD; high frequencies depend on IID.Low frequencies depend on ITD; high frequencies depend on IID.

IID and ITDIID and ITD

Congenitally blind individuals are better at Congenitally blind individuals are better at sound localization.sound localization.

Brain plasticity appears to support this.Brain plasticity appears to support this.

This plasticity is seen in both young and This plasticity is seen in both young and somewhat later cases of deafness.somewhat later cases of deafness.

Cocktail party effectCocktail party effect

Play a tone to one ear.Play a tone to one ear. Adding noise to that ear blocks the tone.Adding noise to that ear blocks the tone. Adding noise to the other ear unblocks the Adding noise to the other ear unblocks the

tone.tone. This is binaural unmasking. (Note the This is binaural unmasking. (Note the

confusing definition in B&S.)confusing definition in B&S.)

Cocktail party effectCocktail party effect

Binaural masking-level difference (BLMD) = Binaural masking-level difference (BLMD) = difference in audibility between monaural and difference in audibility between monaural and binaural cases.binaural cases.

Unmasking is apparently caused by Unmasking is apparently caused by localization of tone in one place and noise in localization of tone in one place and noise in another.another.

Cocktail party effectCocktail party effect

Hearing one’s voice attracts attention.Hearing one’s voice attracts attention.

This suggests that you are normally processing the This suggests that you are normally processing the background information in the “background”.background information in the “background”.

There is a vast literature on dichotic listening. This There is a vast literature on dichotic listening. This attempts to study, among other things, how attention attempts to study, among other things, how attention influences what auditory information is processed.influences what auditory information is processed.

MislocalizationMislocalization

Happens most often with sounds directly in Happens most often with sounds directly in front or directly in back.front or directly in back.

More common with sounds of a narrow band More common with sounds of a narrow band of frequencies; reduced with broadband noise.of frequencies; reduced with broadband noise.

Reduced with reflecting surfaces.Reduced with reflecting surfaces.

Mislocalization compensationMislocalization compensation

1.1. When IID and ITD cues fail, turn your head.When IID and ITD cues fail, turn your head.

2.2. Pinnas of ears helps.Pinnas of ears helps. Verify this with headphones or earmuffs.Verify this with headphones or earmuffs. Especially useful in cases of localization of elevation.Especially useful in cases of localization of elevation. Comparisons of localizations with recordings in one’s Comparisons of localizations with recordings in one’s

own ears versus those in others’ ears shows difference.own ears versus those in others’ ears shows difference. Comparisons of localizations with materials in ear folds.Comparisons of localizations with materials in ear folds.

Sound through headphonesSound through headphones Music is often localized in your head; not in external space.Music is often localized in your head; not in external space.

The reason is that the sounds are recorded from several The reason is that the sounds are recorded from several microphones near the musicians.microphones near the musicians.

To have an auditory image, one has to use just two To have an auditory image, one has to use just two microphones to record.microphones to record.

One must also not move ones head.One must also not move ones head. Scientists are trying to develop a headphone system that can Scientists are trying to develop a headphone system that can

compensate for head movements.compensate for head movements.

Mislocalization with eyes and earsMislocalization with eyes and ears

Visual dominance over Visual dominance over auditory informationauditory information

Eyes mislead about Eyes mislead about sound location:sound location: In movie theaters.In movie theaters. VentriloquismVentriloquism PseudophonePseudophone

Reasons for visual dominanceReasons for visual dominance

Echoes are misdirections, but light does not so Echoes are misdirections, but light does not so often reflect.often reflect.

Light travels faster than sound, so provides a Light travels faster than sound, so provides a more nearly instantaneous measure of location.more nearly instantaneous measure of location.

Visual acuity and localizationVisual acuity and localization

If you have a small region of high acuity, you If you have a small region of high acuity, you had best be able to use audition to guide your had best be able to use audition to guide your direction of it.direction of it.

If you have a small region of high acuity, you had best be able If you have a small region of high acuity, you had best be able

to use audition to guide your direction of it.to use audition to guide your direction of it.

Sound localization: DistanceSound localization: Distance

People are good indoors, since there are People are good indoors, since there are echoes.echoes.

People are poor outdoors tending to People are poor outdoors tending to underestimate distances.underestimate distances. They use intensity to measure.They use intensity to measure. Moving in the direction of the sound is helpful e.g. Moving in the direction of the sound is helpful e.g.

auditory looming.auditory looming.

Auditory LoomingAuditory Looming

As an approaching object makes a sound, the As an approaching object makes a sound, the object looms forward.object looms forward.

Humans overestimate the change in sound between Humans overestimate the change in sound between approaching and receding. (Frequency, approaching and receding. (Frequency, loudness?).loudness?).

Approaching sounds seems closer than they really Approaching sounds seems closer than they really are.are.

Monkeys are susceptible to auditory loom.Monkeys are susceptible to auditory loom.

Auditory and visual interactionsAuditory and visual interactions

Two black spots moving toward each other Two black spots moving toward each other then back is ambiguous betweenthen back is ambiguous between CollidingColliding One passing behind the otherOne passing behind the other

Properly timed sounds render the image Properly timed sounds render the image unambiguous.unambiguous.

Auditory and visual interactionsAuditory and visual interactions

Replicated with fMRI.Replicated with fMRI.

With bouncing (hence multimodal processing) With bouncing (hence multimodal processing) more areas of the brain are active.more areas of the brain are active.

With bouncing (hence multimodal processing) With bouncing (hence multimodal processing) each area of the brain was less active than in a each area of the brain was less active than in a purely visual or purely auditory task.purely visual or purely auditory task.

Auditory and visual interactionsAuditory and visual interactions

Guttman, Gilroy, & Blake, (2004).Guttman, Gilroy, & Blake, (2004). Subjects compared two “visual rhythms.”Subjects compared two “visual rhythms.” Visual rhythms consist of gratings of light and dark Visual rhythms consist of gratings of light and dark

bars that moved in rapid and unpredictable ways.bars that moved in rapid and unpredictable ways. Subjects were asked to judge whether two successive Subjects were asked to judge whether two successive

visual rhythms were the same or different.visual rhythms were the same or different. Version 1: Musical rhythm matched movements of Version 1: Musical rhythm matched movements of

gratings.gratings. Version 2: Musical rhythm did not match movements Version 2: Musical rhythm did not match movements

of gratings.of gratings.

Auditory and visual interactionsAuditory and visual interactions

Guttman, Gilroy, & Blake, (2004) results:Guttman, Gilroy, & Blake, (2004) results:

People’s judgments were heavily influenced by People’s judgments were heavily influenced by sound.sound.

When the auditory rhythm matched the visual When the auditory rhythm matched the visual rhythm, subjects were nearly perfect.rhythm, subjects were nearly perfect.

When the auditory rhythm did not match the When the auditory rhythm did not match the visual rhythm, subject performed some better visual rhythm, subject performed some better than chance.than chance.

Auditory and visual interactionsAuditory and visual interactions

Shams, Kamitani, & Shimojo, (2000).Shams, Kamitani, & Shimojo, (2000). Single flash presented alone seen as single Single flash presented alone seen as single

flash.flash. Single flash presented in conjunction with an Single flash presented in conjunction with an

auditory click seen as a double flash.auditory click seen as a double flash.