slides l4 phon acquisition.ppt - university of...

Homework 1

• Colorless green ideas sleep furiously

• Arguments for mental grammar ≠ Arguments for innate knowledgeArguments for innate knowledge

• Creativity / expressivity

• Hypothesis testing

Review of phonology

• Phonemes vs. allophones• Phonemic analyses (two steps)Phonemic analyses (two steps)• Contrastive (distinctive) vs.

complementary distributioncomplementary distribution

Examine the distribution of [x] and [ç]. [x] = voiceless velar fricative[ ] i l l l f i i[ç] = voiceless palatal fricative

Apply the two steps of phonemic analyses. If pp y p p ythe two sounds are in complementary distribution, then

a) list the environments (neighboring sounds)b) state a generalization (x occurs in y, a

i b)occurs in b)c) state a rule.

Ling 240Ling 240

Acquisition of phonemic categoriesg

phonetic and phonemic categories

Categorization of speechCategorization of speech sounds

• difference between physical level p yand mental level

• how are mental categories used in speech perception?p p p

• how are mental categories acquired?

Physically (phonetically)t d¬

dph

thd

pb

t¬

Mentally (phonologically):C t i i E li hCategories in English

t d¬d

ph

thd

pb

t¬

English Sindhi

/p/ /p/ /ph/p

[p] [ph] [p] [ph]

Categories are not determined by the physical properties of theby the physical properties of the speech sounds

Physically: a continuum

Voicing continuum

ph p bph …………. p …………. b

th ………….. t …………. d

Mentally: discrete categoriesMentally: discrete categories

Gradient vs. Categorical

tall - short vs. pass - failhappy - sad vs dead - alivehappy sad vs. dead alive

Gradability

tall or short?• gradability: in betweengradability: in between• comparison: X is taller than Y

d d i l X• dependence on a comparison class: X can be tall in one context but short in

thanother

Discreteness

dead or alive

• X is either dead or not no in between• X is either dead or not -- no in between

• X cannot be more dead than Y

• X cannot be dead in one context but not in anotherin another

Going back to speech sounds

Voicing continuum

ph p bph …………. p …………. b

th ………….. t …………. d

Voice onset time

• VOT = the interval between the release of a closure and the start of the voicingg

Voice Onset Time (VOT)

60 msec

English VOT production

Discrimination

D 0ms 20msD D

20ms 40msD T

40ms 60msT T

Perceiving VOT

‘Categorical Perception’

Categorical PerceptionCategorical Perception

Humans perceive phonemes categoricallyHumans perceive phonemes categorically

DA1 DA2 TA1 TA2

0 20 40 60 80VOT in milliseconds

Categorical perception

• The mind imposes discrete, abstract categories which do not exist in the gphysical world

• Gradations in the phonetic categoriesGradations in the phonetic categories are ignored

Any questions so far?

• Mental vs. physical• Categorical vs gradientCategorical vs. gradient• VOT

C t i l ti• Categorical perception

But wait a second…

• What about children?• They need to learn these abstract y

phonological constructs, but they are only exposed to the actual physical instances of sounds – they don’t have direct access to phonemes (which are in adult’s lexicon)adult’s lexicon)

• So, how can they learn phonemes of their native language?their native language?

Do they have phonemicDo they have phonemic categories?

Wh t biliti hild b ith?• What abilities are children born with?• What abilities are specific to humans?• What abilities are specific to the

linguistic system?g y

Is phoneme discrimination innate or

l d?learned?

Is phoneme discriminationIs phoneme discrimination innate?

• Hypothesis A: Innate ability to discriminate all possible phoneme distinctions (in any language)

• Hypothesis B: children learn to discriminate the contrasts in their language

• Hypothesis C: Something in between… some contrasts are innate, others learnedlearned

Do newborns perceiveDo newborns perceive phonemes categorically?p g y

Eimas et al 1971Eimas et al., 1971

Can newborns perceive categorically?

BA PA1 PA2BA PA1 PA2

0 20 40 60 800 20 40 60 80VOT in milliseconds

How do newborn babiesHow do newborn babies perceive speech sounds?

• Speech perception is innate: infants perceive categorically (Hyp. Ai)p g y ( yp )

• Untuned sensitivity: infants perceive diff b t t t i ll (Hdifferences but not categorically (Hyp. Aii)

• Infants are insensitive to differences between speech sounds (Hyp B)between speech sounds (Hyp. B)

But how can you test what infants perceive?perceive?

High AmplitudeHigh Amplitude Sucking Procedure

• Pacifier contains sensor to monitor sucking rates

• Each time infantEach time infant sucks pacifier, a stimulus is playedstimulus is played

StimulusStimulus

BA1 BA2 PA1 PA21 2 1 2

0 20 40 60 80VOT in millisecondsVOT in milliseconds

Hi h A lit dHigh Amplitude Sucking Procedureg

• Initially sucking rate increases (novelty)

• Then decreases• Decline in response

= habituationhabituation

LSCP Infant Lab

High AmplitudeHigh Amplitude Sucking Procedure

When sucking rate declines to a setdeclines to a set point (habituation criterion)criterion),auditory stimulus is changed

LSCP Infant LabLSCP Infant Lab

TestTest

BA1 BA2 PA1 PA21 2 1 2


High Amplitude S kiSucking

ProcedureIf sucking rate

increases, ,then we know the

infant has detectedinfant has detected the change

• The renewed• The renewed response = is dishabituationdishabituation

LSCP Infant Lab

Predictions: Hypothesis A(i)Predictions: Hypothesis A(i) ? ?

BA1 BA2 PA1 PA21 2 1 2


Predictions: Hypothesis A(i)Predictions: Hypothesis A(i) iRemain

habituateddishabituate

BA1 BA2 PA1 PA21 2 1 2


Predictions: Hypothesis A(ii)Predictions: Hypothesis A(ii) ? ?

BA1 BA2 PA1 PA21 2 1 2


Predictions: Hypothesis A(ii)Predictions: Hypothesis A(ii) di h bi di h bidishabituate dishabituate

BA1 BA2 PA1 PA21 2 1 2


Predictions: Hypothesis BPredictions: Hypothesis B ? ?

BA1 BA2 PA1 PA21 2 1 2


Predictions: Hypothesis BPredictions: Hypothesis B i iRemain

habituatedRemain

habituated

BA PA1 PA21 2


Results

phonemic acoustic

High Amplitude kiSucking

Eimas et al. 1971

Results = Hypothesis A(i)Results = Hypothesis A(i) iRemain

habituateddishabituate

BA1 BA2 PA1 PA21 2 1 2


ConclusionsConclusions

Newborns perceive speech sounds categorically

Categorical perception of h d i i tspeech sounds is innate

Newborns are universal listeners

Newborns are sensitive to every phonological distinction yet testedphonological distinction yet tested

Is categorical perception of speech sounds unique tospeech sounds unique to

humans?Or do other animals do this too?

Do other animals perceiveDo other animals perceive phonemes categorically?

K hl & Mill 1978 t t hi hillKuhl & Miller 1978: test chinchillas and humans with identical stimuli

ChinchillasChinchillas

Avoidance Conditioning Procedure

Sh k i d ith h d tShock paired with speech sound at one end of continuum (A)

0 80PAVOT in milliseconds


Sound at other end (B) paired with safety

0 80VOT in milliseconds

BA


Animal learns to run to other side of cageAnimal 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?

Sta R n? ? ? ?Stay Run? ? ? ?

PABA

Predictions

100Categorical Perception

708090

ed [b

]

Categorical PerceptionGraded Perception

405060

nt la

belle

10203040

Perc

en

010

0 10 20 30 40 50 60 70 80

Voice Onset Time (ms)

Results

Kuhl & Miller, 1978

100

8090

100

[b]

English Speakers

50

6070

labe

lled

2030

40

Perc

ent l

010

20P

0 10 20 30 40 50 60 70 80


Kuhl & Miller, 1978

100

8090

100

[b]

English SpeakersChinchillas

50

6070

labe

lled

2030

40

Perc

ent l

010

20P

0 10 20 30 40 50 60 70 80


ConclusionsConclusions

Categorical perception of speech sounds is not species-specificspecific (even chinchillas can do it!)

Becoming a Native Listener

What develops in speech perception?perception?

Universal Phonetic Spacep

EnglishJapanese EnglishJapanese

French

Universal phonetic inventoryp y

Languages differ in their g gphonetic inventories

In English /r/ and /l/ are separateIn English /r/ and /l/ are separate phonemes

Ex: rate vs. lateN t i JNot so in Japanese

Languages differ in their g gphonetic inventories

I E li h th diff b tIn English the difference between (alveolar) /d/ and retroflex /D/ is ( )not phonemic

In Hindi it isIn Hindi it is

Cross-Language Differences

English vs HindiEnglish vs. Hindi

alveolar [d]?

retroflex [D] ?


English infants can distinguish Hi di /d/ d /D/Hindi /d/ and /D/Japanese infants can distinguishJapanese infants can distinguish between /l/ and /r/


Infants perceive speech t i llcategorically

Newborns are sensitive to almostNewborns are sensitive to almost every phonological distinction yet t t dtested

Newborns are universalNewborns are universal listeners

In contrast, adults have difficulty , ydiscriminating speech sounds that are not contrastive in their nativeare not contrastive in their native language

Studies by Werker et alStudies by Werker et al

• Goals?

• Methodology?

Testing Across the LifespanTesting Across the Lifespan

• HAS works only with infants from birth to 4 monthsbirth to 4 months

• Adults & children can be asked to detect a change

• The Conditioned Head Turn• The Conditioned Head Turn Paradigm can be used for 6-12

th ld i f tmonth-old infants

Experimenter p(headphones)

Infant

Parent(headphones)

Experimenterp

Visual ReinforcerVisual Reinforcer (VR)

Toy that lights up y g pand moves at the experimenter’s commandcommand

C t l fControls for sound stimuli and the VR

Conditioned Head Turn Paradigm

Kuhl Lab, U Washington, 1992

C di i i H d TConditioning Head Turn

• Infant Trained with 2 clearly different auditory stimuli (bell anddifferent auditory stimuli (bell and whistle)

h ti th d h th–each time the sound changes the toy is activated

–next, toy is activated only if the sound changes AND the babysound changes AND the baby turns to look at it

Conditioned Head TurnConditioned Head Turn

• Child hears Stimulus 1 (/ba/)• Child hears Stimulus 1 (/ba/) repeatedly

• Then Stimulus 2 is presented (/da/)• If child detects difference they• If child detects difference, they

should turn to look at the toy when the stimulus changesthe stimulus changes

• If they do not detect it, they y yshouldn’t turn

Conditioned Head Turn Paradigm

Kuhl Lab, U Washington, 1992

Werker 1995Werker 1995

Subjects: Hindi adultsEnglish AdultsEnglish AdultsEnglish 6-8 month-olds

Testing /ba/ vs. /da/g/Ta/ vs. /ta//th / /dh //tha/ vs. /dha/


/ba/ vs. /da/ Hindi and Englishg

/T / /t / O l Hi di/Ta/ vs. /ta/ Only Hindi

/tha/ vs. /dha/ Only Hindi

Results

Werker, 1995

Conclusions English-speaking infants could

d t t diff i tidetect differences in non-native contrasts

English-speaking adults were very b d t itbad at it

When does decline in performance take place?performance take place?


Testing the same group of infants at different points in timeinfants at different points in time

• 6-8 months• 8-10 months

10 12 months• 10-12 months

ResultsResults

Werker, 1995

Werker studies: Conclusion

Ability to perceive non-Ability to perceive nonnative contrasts

declines in 1st yearWerker and Tees 1984

What is responsible for theWhat is responsible for the change?

How do babies become adults?How do babies become adults?

First proposal:First proposal: Maintenance/loss Hypothesis

• role of experience is to maintain pperceptual sensitivitiesl k f l d t l f• lack of exposure leads to loss of perceptual abilityp p y

Maintenance/loss in vision

• In visual cortex, cells specifically designed to respond to certain g pkinds of input (vertical lines, horizontal lines))

• Cells atrophy if deprived of relevant input during critical periodinput during critical period

Hubel and Wiesel 1965

Maintenance/loss forMaintenance/loss for perception of speech sounds

• Does a lack of exposure to certain contrasts lead to permanent loss of sensitivity topermanent loss of sensitivity to these contrasts?

• (atrophy of specialized neurons)

Problems for theProblems for the Maintenance/loss Hypothesis

• Prediction: decline in sensitivity• Prediction: decline in sensitivity following lack of exposure h ld b dshould be permanent and

absolute


Predictions are not borne out: (1)( )• Adults CAN perceive non-native

contrastscontrasts -- but only in non-speech tasksy

(bucket study, Zulu clicks)


Predictions are not borne out: (2)( )• Children older than 12 months

can mo e to a ne co ntr andcan move to a new country and acquire native phonology gy(without accent)

Alternative Hypothesis:Alternative Hypothesis: Functional Reorganization

• no absolute hardware changes in dit tauditory system

• development of a linguistic system p g ythat imports a subset of the contrasts from the auditory systemcontrasts from the auditory system

Conclusions

• As babies (become ready to) acquire a linguistic systemacquire a linguistic system (words) in their first year, they “learn” which distinctions need to be represented in thatto be represented in that system

Conclusions

• Other distinctions do not get used in the linguistic systemused in the linguistic system (though they are still available in non-linguistic domains)

Conclusions

So, what changes during the first year?what changes during the first year?

answer:answer: the baby starts to acquire a linguistic system i e the phonemic inventorysystem, i.e., the phonemic inventory of their target language

Conclusions

thus, universal discrimination of speechuniversal discrimination of speech sounds is not specific to linguistic

tsystem

Categorical perception ofCategorical perception of phonemic contrasts

• Innate? Yes

• Unique to humans? No

• General cognition or specific to linguistic system? Bothg y Both

Other issues

• critical period

If you want to learn more about these issues, read this book!

Jusczyk 1997. MIT Press

For tomorrow

• Review for exam• HW2 due!HW2 due!• Come to class with questions

A d th ’ll h (1 h )• And then we’ll have an exam (1 hour)

slides l4 phon acquisition.ppt - university of...

Documents