Psych 156A/ Ling 150: Psychology of Language Learninglpearl/courses/psych156A_2009wi… · ·...

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Psych 156A/ Ling 150:Psychology of Language Learning

Lecture 2Sounds I

Announcements

Review questions for introduction to languageacquisition available

Homework 1 available (due 1/15/09)

Sean’s office hours now available:Mondays, 12:30-2:30pm in SSL 491

Learning Sounds

big vs. pig

Lisa = Risa for some ofmy Japanese friends

Learner’s job: parse continuous stream ofspeech into sentences, clauses, words,syllables, and phonemes (contrastive soundsthat signal a change in meaning)

Phonemes are language-specific - r/l isa phonemic contrast in English but notin Japanese

Kids of the world require knowledge ofphonemes before they can figure outwhat different words are - and whendifferent meanings are signaled bydifferent words

Sounds of Language (Speech Perception)

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About Speech Perception

Important: Not all languages use the same contrastive sounds.

Languages draw from a common set of sounds (which can berepresented by the International Phonetic Alphabet (IPA)), but only usea subset of that common set.

Child’s task: Figure out what sounds their native language usescontrastively.

AcousticAcoustic

Innate

ConstructedPhonemicPhonemicmeaningful sounds in the

language: “contrastive sounds”or phonemic contrasts

Speech Perception: Computational Problem

Divide sounds into contrastive categories (phonemes)Here, 23 acoustically-different sounds are clustered into 4contrastive categories. Sounds within categories areperceived as being identical to each other.

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Categorical PerceptionCategorical perception occurs when a range of stimuli that differ

continuously are perceived as belonging to only a fewcategories with no degrees of difference within a givencategory.

Actual stimuli

Categorical Perception of stimuli

Acoustic-Level Information

Includes: timing and frequencyIncludes: timing and frequencyTones: frequency

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Includes: timing and frequencyIncludes: timing and frequencyTones: frequency (close-up)


Includes: timing and frequencyIncludes: timing and frequencyTones: frequency (close-up)

Vowels combine acoustic energy at a number of different frequencies

Different vowels ([a] “ah”, [i] “ee”, [u] “oo” etc.) contain acoustic energy atdifferent frequencies

Listeners must perform a ‘frequency analysis’ of vowels in order toidentify them(Fourier Analysis)


Language soundsLanguage sounds


Language soundsLanguage soundsMale Vowels

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Language soundsLanguage soundsMale Vowels (close up)


Language soundsLanguage soundsFemale Vowels


Language soundsLanguage soundsFemale Vowels (close up)

Synthesized Speech

Allows for precise control of sounds

Valuable tool for investigating perception

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Language soundsLanguage soundsTiming: Voicing


Language soundsLanguage soundsTiming: Voice Onset Time (VOT)

60 ms

English VOT productionNot uniform - there are 2 categories (distribution is bimodal)

Perception of stimuli: 2 categories

Perceiving VOT

‘Categorical Perception’: dQ vs. tQ

Decision between d/tIdentification task:“Is this sound dQ or tQ?”

Time to make decision

Longer decisiontime at categoryboundaryMore uncertainty/

error at categoryboundary

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Discrimination Task“Are these two sounds the same or different?”

Same/Different0ms 60ms







Why is this pair difficult?

(i) Acoustically similar?

(ii) Same Category?


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D T

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Across-Category Discrimination is Easy

Within-Category Discrimination is Hard

Cross-language Differences

R L

R L

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Cross-Language Differences

Identification task:

English speakers candiscriminate r and l, andseem to show a similarpattern of categoricalperception to what we sawfor d vs. t

R -----------------------> L

Cross-Language DifferencesDiscrimination task:

English speakers have higher performance at the r/l category boundary,where one sound is perceived as r and one sound is perceived as l.Japanese speakers generally perform poorly (at chance), no matter whatsounds are compared because r and l are not contrastive for them.

Cross-Language Differences

English vs. Hindi

alveolar [d]

retroflex [D]?

KidsKids……

……vsvs. adults. adults

Adults can’t, especially without training - even if thedifference is quite acoustically salient.

This ability to distinguish sound contrastsextends to phonemic contrasts that are non-native. (Japanese infants can discriminatecontrasts used in English but that are notused in Japanese, like r/l.) This goes forboth vowels and consonants.

So when is this ability lost?

And what changes from childhood to adulthood?

Perceiving sound contrasts

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A useful indirect measurement

Head Turn Preference Procedure

Infant sits on caretaker’s lap. Thewall in front of the infant has agreen light mounted in the centerof it. The walls on the sides of theinfant have red lights mounted inthe center of them, and there arespeakers hidden behind the redlights.

Sounds are played from the twospeakers mounted at eye-levelto the left and right of the infant.The sounds start when the infantlooks towards the blinking sidelight, and end when the infantlooks away for more than twoseconds.


A useful indirect measurement

Thus, the infant essentiallycontrols how long he or she hearsthe sounds. Differentialpreference for one type of soundover the other is used asevidence that infants can detect adifference between the types ofsounds.


A useful indirect measurement Head Turn Preference Procedure Movie

http://www.youtube.com/watch?v=mZAuZ--Yeqo

“How Babies Learn Language”(first part, up to about the 2 minute mark)

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Speech Perception of Non-Native SoundsComparing perceptual ability

Werker et al. 1981: English-learning 6-8 month olds compared against English &Hindi adults on Hindi contrasts



Hindi adults can easilydistinguish sounds thatare used contrastively intheir language



English adults areterrible (below chance),though there is somevariation depending onwhich sounds are beingcompared



English infants betweenthe ages of 6-8 monthsaren’t quite as good asHindi adults - but they’recertainly much betterthan English adults!They haven’t yetlearned to ignore thesenon-native contrasts.

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Sound-Learning Movie

Infant Speech Discrimination

http://www.youtube.com/watch?v=GSIwu_Mhl4A

When Change Happens

But when after 6-8 months is the ability to lost? Werker & Tees (1984)

Testing ability to distinguishSalish & Hindi contrasts

When Change Happens



Control (make sure experiment is doable by infants):Hindi and Salish infants do perfectly

When Change Happens



English 6-8 month-olds do well

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When Change Happens



English 8-10 month-olds do less well

When Change Happens



English 10-12 month-olds do very poorly

When Change Happens



Implication: The ability to distinguish non-native contrasts is lost by 10-12 months.Change seems to be happening between 8-10 months.

When Change Happens


Doing a longitudinal study withEnglish infants (where thesame infants are tested overtime), change seems tohappen somewhere around 8-10 months, depending on thesound contrast.


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How Change Happens

Infants maintain contrasts being used in their language andlose all the others.

Maintenance & Loss Theory

Patricia Kuhl

Natural boundaries(acoustically salient)

“Perceptual Magnet”

How Change Happens



Patricia Kuhl

Sounds from Language 1


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How Change Happens



Patricia Kuhl

Category boundaries that are maintainedto keep these sound clusters distinct


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How Change Happens



Patricia Kuhl

Sounds from Language 2


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How Change Happens



Patricia Kuhl


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Category boundaries that are maintainedto keep these sound clusters distinct

How Change Happens



Patricia Kuhl


Cross-linguistic variation in which contrasts aremaintained, depending on language input

How Change Happens

Prediction for performance on non-native contrasts over time:


Loss of discrimination ability is permanent and absolute

Should never be able tohear this distinction again

How change happensProblems with the Maintenance & Loss Theory

Non-linguisticperception

If it doesn’t sound like speech, adults cantell the difference. Werker & Tees (1984)showed this with truncated portions ofsyllables of non-native contrasts. Theytold subjects the sounds were waterdropping into a bucket, and to tell themwhen the bucket changed. Adults whocould not perceive the difference whenthey heard the entire syllable couldperceive the difference when theyprocessed the consonant soundsseparately as a non-linguistic sound - likewater dropping into a bucket.

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Pisoni et al. (1982), Werker & Logan (1985): adultscan be trained if given enough trials or tested insensitive procedures with low memory demands.

Maintenance & Loss would predict that this abilityshould be irrevocably lost - and it shouldn’t matterhow much training adults receive, or how the task ismanipulated to help them.

Some non-native contrasts are easy for older infants andadults to discriminate, even though these sounds are neverheard in their own languages. (Click languages (Zulu) - clicksounds like “tsk tsk” nonspeech)

http://hctv.humnet.ucla.edu/departments/linguistics/VowelsandConsonants/course/chapter6/zulu/zulu.html


How change happens

Changes attested experimentally reflectoperation of postperceptual processesthat kick in for language sounds.

Data distributions determine what thecategory boundaries are in the filter.Importantly, constructing this filter doesnot affect base-level sound perception.

Perception of sound

Non-linguistic level

Linguistic level

consciousperceptionoflanguagesound

Janet Werker

Unconscious filter imposed

Another theory: Functional reorganization

How change happens

Very young infants respond to any detectable variation -so they can pick up any salient contrasts in surroundinglanguage. Adults have a bias for phonemic contrastssince those are the ones relevant to language. If in anon-language setting, adults can distinguish non-nativecontrastive sounds.

Explanatory power: the whole story

Another theory: Functional reorganization

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Learning Sounds: Recap

One of the things children must do is figure out what the meaningfulcontrastive sounds (phonemes) in their native language are.

Phonemes vary from one language to another.

Children initially can hear many contrastive sounds, even non-nativeones. However, they seem to have lost this ability by 10-12months and instead only consciously hear the contrastive soundsof their native language.

Evidence suggests that this perceptual change is a specializedunconscious filter that is only active when the brain believes it isprocessing language sounds.

Questions?

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