Infant Speech Perception LSCP Infant Lab Outline Introduction to - - PowerPoint PPT Presentation

Infant Speech Perception

LSCP Infant Lab

Outline

• Introduction to Phonology
• Problem of Speech Perception
• Testing two theories of speech perception

– Infant Categorical Perception – Cross-species categorical perception – The use of visual cues

Universal Structural Design

_____________________________

English Consonants

• 1. Introduction to Phonology

15

Phonemes

Vowels: unimpeded sound through vibrating vocal cords Vary by:

• Placement of tongue

– ee is high front – ah is low back

• Rounding of lips

Phonemes

Consonants: Sound is impeded in some way Vary by:

• 1. Place of articulation

m, p, b n, t, d ng, k, g

Phonemes

Consonants vary by

• 2. Kind of articulation:
• stop: p, b, d
• nasal: n,m
• fricative: ch, th, f
• 3. Voicing, Nasality, Creaky Voice, Clicks
• voiced: b, d, z....
• voiceless: p, t, s...

Phonemes are bundles of features

• P: bilabial, voiceless, stop
• B: bilabial, voiced, stop
• S: dental, voiceless, fricative

Phonemes are bundles of features

p: bilabial, voiceless, stop s: dental, voiceless, fricative

Evidence

• Phonological features participate in speech

errors

• Phonological rules typically refer to features:

– plural marker assimilates the voicing of the consonant before it – cup/s/, beet/s/, back/s/ – cub/z/, bead/z/, bag/z/

Phonemes Phonemes

?

• 2. A Brief Tour of Speech

Perception

10:25 15

The String Fallacy

• Speech sounds seem separable and

sequential: like beads on a string

• Reality:

– Speech sounds overlap (co-articulation) – Each speech sound is affected by the elements around it

Two problems of speech perception

• Segmentation

– how do we discover where one phoneme ends and the next begins

• Invariance:

– How can we identify a phoneme when it’s sound changes depending on context?

We won’t be answering these questions today

One Hint: some complex features of a speech sound may stay constant

Speech sounds vary along a continuum

Yet we perceive them as discrete categories

B D G

Categorical Perception: Identification

% identification

Categorical Perception: Discrimination

• 3. Where does this ability come

from?

10:40 12

Two theories

• The Motor Theory:

– perception is informed by our innate knowledge

• f articulation
• The Auditory Theory:

– speech perception is based solely on auditory properties of speech

We have innate knowledge of how articulation changes depending on context

Motor Theory

Innate knowledge of articulation Used to predict changes in sound wave and recover phonemes

Motor Theory

Auditory system breaks speech into phonemes

• innate property of sensory system or
• perceptual learning

Auditory Theory

Contrasting the two theories

The Motor Theory

• 1. Perception is based on

production

• Process:

– Determine what articulatory gestures a speaker made – Then identify phoneme

The Auditory Theory

• 1. Perception by generic

auditory mechanisms

• Process

– Auditory system transforms sound wave so phonemes available

Contrasting the two theories

The Motor Theory

• 2. Perception is species

specific

– Speech production and speech perception evolved together – Only humans speak, so

• nly humans have SP

system

The Auditory Theory

• 2. Not species specific

– Production system evolved to make use of existing auditory capacities – No special adaptations to speech

Contrasting the two theories

The Motor Theory

• 3. SP is innate

– Tacit knowledge of articulation given by evolution

The Auditory Theory

• 3. SP may be innate

– Innate properties of the auditory system may be adequate to isolate phonemes – Or Perceptual Learning may be required

• 4. Is Speech Perception Innate?

10:52 18

Do newborns perceive phonemes categorically?

Predictions:

• If categorical perception requires

knowledge of contrastive phonemes: NO

• If it requires exposure to language: NO
• If it is an innate ability: YES

But how can you test immobile infants?

High Amplitude Sucking Procedure

• Infant given a pacifier
• Contains sensor to

monitor sucking rates

• Each time the infant

sucks the paci, a stimulus is played

LSCP Infant Lab

High Amplitude Sucking Procedure

• Initially sucking rate

increases (novelty)

• Then it decreases
• This decline in

response is habituation

LSCP Infant Lab

High Amplitude Sucking Procedure

• When sucking rate

declines to set point (habituation criterion)

• The computer

switches the auditory stimulus

LSCP Infant Lab

High Amplitude Sucking Procedure

• If sucking rate

increases

• Then we know the

infant has detected the change

• The renewed response

is dishabituation

LSCP Infant Lab

Stimuli for the Eimas Study

Voice Onset Time: time btw consonant release and vocal cord vibration S1 S2 S3 20 40 60 80 VOT in milliseconds

Stimuli for the Eimas Study

Phoneme Category Boundary at 25ms BA PA1 PA2 20 40 60 80 VOT in milliseconds

Predictions

Within Category Between Category Innate Categorical Perception

remain habituated dishabituate

Untuned Sensitivity

dishabituate dishabituate

Insensitive

remain habituated remain habituated

Stimuli from different phonological categories are distinguished

Time SPM sucks per minute

“PA1” “BA”

Eimas, et al., 1971

But stimuli from the same phonological category are not

“PA2” “PA1”

SPM sucks per minute Time

Eimas, et al., 1971

Speech Perception is Innate

Predicted by Motor Theory

• Speech Perception

driven by innate knowledge of articulation Consistent with Auditory Theory

• Speech perception due

to innate structure of auditory system

• 5. Is Speech Perception

Species Specific?

11:10 10

Do other animals perceive phonemes categorically?

• Kuhl & Miller, 1978: test chinchillas and

humans with identical stimuli

• Human Task: identification (b or p)
• Chinchillas: avoidance conditioning

Avoidance Conditioning Procedure

Shock paired with speech sound at one end of continuum (A) 80 VOT in milliseconds

PA

Avoidance Conditioning Procedure

Sound at other end (B) paired with safety 80 VOT in milliseconds

BA

Avoidance Conditioning Procedure

Animal learns to run to other side of cage when it hears sound A but stay after B What will they do for sounds in between? stay ? ? ? run

Predictions

10 20 30 40 50 60 70 80 90 100 10 20 30 40 50 60 70 80

Voice Onset Time (ms) Percent labelled [b]

Categorical Perception Graded Perception

Kuhl & Miller, 1978 10 20 30 40 50 60 70 80 90 100 10 20 30 40 50 60 70 80

Voice Onset Time (ms) Percent labelled [b]

English Speakers

Kuhl & Miller, 1978 10 20 30 40 50 60 70 80 90 100 10 20 30 40 50 60 70 80

Voice Onset Time (ms) Percent labelled [b]

English Speakers Chinchillas

Not all aspects of speech perception are species specific

Contrary to Motor Theory

• Claim: only humans

have knowledge (innate or learned) of articulation Consistent with Auditory Theory

• General auditory

abilities adequate for (some aspects of) speech perception

• 6. Is Speech Perception

Affected by Knowledge of Articulation?

11:20 10

McGurk Effect

• Vary visual information about place of

articulation

– palatal: GA – dental: DA – bilabial: BA

• Vary auditory stimulus (BA→DA→GA)
• Task: phoneme identification

McGurk Effect

• Finding: phoneme category boundary

affected by visual information

– sound BA + visual GA = percept DA

• Adult speech perception affected by visual

cues

• Did they learn it?

Do infants know visual cues to articulation?

• No evidence of visual cues influencing

categorization

• But can infants match sound with the

correct mouth shape?

Preferential Looking (Kuhl & Meltzoff, 1982

[a]-face [i]-face

a...a....a...a..a

[a]-face [i]-face

Speech Perception is influenced by information about articulation

Predicted by Motor Theory

• Innate connection btw

production and perception Inconsistent with Auditory Theory

• Though a visual-

auditory theory might explain this

• Would require

perceptual learning

Provisional Conclusions

• Speech Perception makes use of auditory

mechanisms which evolved prior to language

– These abilities are innate

• Speech Perception also makes use of our

knowledge of articulation

– This ability MAY be innate

McGurk Effect Revisited

McGurk_large.mov

Development of Phonological Representations

Working toward a model….

Syntactic Syntactic Phonological Phonological Phonetic Phonetic Auditory Auditory Articulatory Articulatory Lexical Lexical

Innate? Constructed

What’s innate?

• Auditory abilities
• Articulatory rudiments

– Not developed – Desire to coo and babble even in deaf infants

Auditory Auditory

Innate

Auditory Auditory Articulatory Articulatory

Innate

Newborns are universal listeners

• Infants perceive speech categorically
• Newborns are sensitive to every

phonological distinction yet tested

• What happens to the categories that are not

used in the language that they learn?

English VOT perception

English VOT production

• Not uniform
• 2 categories

English s - sh

• 2 categories
• Notice also

a shift in curve with a or u

• Cue trading

Developmental changes

• English

versus Japanese r - l

Developmental changes

• English

versus Spanish VOT

Testing Across the Lifespan

• Habituation paradigms work only with

young infants

• Adults & children can be asked to detect a

change

• The Conditioned Head Turn Paradigm

parallel task for older infants

Conditioned Head Turn Paradigm

Kuhl Lab, U Washington, 1992

Conditioned Head Turn Paradigm

Kuhl Lab, U Washington, 1992

Conditioned Head Turn

• Infant Trained with 2 clearly different

auditory stimuli (bell and whistle)

– each time the sound changes the toy is activated – next toy is activated only if the sound changes AND the baby turn to look at it

Conditioned Head Turn

• Child hears Stimulus 1 (/ba/) repeatedly
• Then Stimulus 2 is presented (/da/)
• If child detects difference, they should turn

to look at the toy when the stimulus changes

• If they do not detect it, they shouldn’t turn

until after the toy is activated

Contrasting Views

Maintenance or Loss Model

• If you don’t use a perceptual ability, you

lose it

• Parallel to aspects of early visual

development

Maintenance or Loss Model

Problems:

• Children older than 1yr can acquire a new

language with no accent

• Many of the relevant sounds appear in

child’s input but not meaningful

• Adults can be trained to make distinctions
• Perceptual distinction is readily available

for non-linguistic tasks

Functional Reorganization

• The newborn has perceptual categories
• Those which are meaningful in the native

language become speech categories

• The remainder are perceived but not

recruited in speech perception

Speech Perception Before Reorganization

Phonetic Phonetic Auditory Auditory Articulatory Articulatory

Innate & Universal

Behavior Behavior

Creation of Phonological Representations

Phonology Phonology Phonetic Phonetic Auditory Auditory Articulatory Articulatory

Innate Constructed & Language Specific

Behavior Behavior

Functional Reorganization

Syntactic Syntactic Phonological Phonological Phonetic Phonetic Auditory Auditory Articulatory Articulatory Lexical Lexical

Innate Constructed

Appears around 10m Appears around 14m

Critical period

• Foreign accent syndrome
• Why are foreign languages hard to

perceive?

• Differences in phonological

categories and phonological rules.

Epenthetic Vowels

• French allows consonant clusters
• Japanese does not
• Japanese loan words add vowels to

break up clusters

Epenthetic Vowels

• Japanese speakers tend to produce

and perceive additional vowels in L2

• Add epenthetic vowel /u/ to break

up clusters

• For French: “ebuzo” & “ebzo”

distinct

• Not for Japanese learner of French

Behavioral results

• Japanese can’t distinguish presence
• r absence of these vowels

Dupoux, Fushimi, Kakehi & Mehler, 1999

ebzo ebuzo

ERP experiment

• habituation, switch

paradigm

– ebuzo…ebuzo…ebzo – ebzo…ebzo….ebuzo

• record EEG & average
• French have early,

middle, late mismatch responses

• Japanese only have late

response

Jacquemot, Pallier, LeBihan, Dehaene & Dupoux, 2002

Early Response

Middle Response

Late response

Problem

• Japanese should detect the

difference at phonetic level

• But supress at the lexical level and

in decision process

• Why do they only have the

late response?

• Could the phonetic response be the

late response?

When are epenthetic vowels added?

Syntactic Syntactic Phonological Phonological Phonetic Phonetic Auditory Auditory Articulatory Articulatory Lexical Lexical

Innate Constructed

Distinction should be available here…. But gone by here