Transcript Class slides 1

Psycholinguistics I
LING 640
What is psycholinguistics about?
Guiding Questions
• What do speakers of a language mentally represent?
• How did those representations get there?
• How are those representations constructed?
• How are those representations encoded?
Language is a Human Specialization
•
•
•
•
•
Species specificity
Within-species invariance
Spontanous development, insensitivity to input
Independence of general intelligence
Selective brain damage
•
The ‘Language Instinct’ [Pinker 1994]; see Gleitman & Newport chapter
[readings] for nice summary
•
These arguments suggest that there’s a coherent object of study, but tell us
very little about its form
We need explicit answers…
• What do speakers of a language mentally represent?
• How did those representations get there?
• How are those representations constructed?
• How are those representations encoded?
Explicit models quickly reveal
surprising complexity
A Simple(-ish) Example
•
Distribution of pronouns/reflexives
– John likes him/himself.
– John thinks that Mary likes him/himself.
•
Infinitival clauses
– John appeared to Bill to like himself.
– John appeared to Bill to like him.
•
But…
– John appealed to Bill to like himself.
– John appealed to Bill to like him.
•
Abstract solution…
– Johni appealed to Billj [PROj to like himselfj ]
Abstraction is a double-edged sword
Abstraction
•
Abstraction is valuable
– Provides representational power
– Provides representational freedom
•
Abstraction is costly
–
–
–
–
Linguistic representations are more distant from experience
This places a burden on the learner - motivation for innate knowledge
This places a burden on comprehension/production systems
(and it makes it harder to know what to look for in the brain)
Sensory Maps
Internal representations of
the outside world. Cellular
neuroscience has discovered
a great deal in this area.
Lab #1
Acoustic Continua and
Phonetic Categories
Frequency - Tones
Frequency - Tones
Frequency - Tones
Frequency - Tones
Frequency - Complex Sounds
Frequency - Complex Sounds
Frequency - Vowels
• Vowels combine acoustic energy at a number of different
frequencies
• Different vowels ([a], [i], [u] etc.) contain acoustic energy
at different frequencies
• Listeners must perform a ‘frequency analysis’ of vowels in
order to identify them
(Fourier Analysis)
Frequency - Male Vowels
Frequency - Male Vowels
Frequency - Female Vowels
Frequency - Female Vowels
Synthesized Speech
•Allows for precise control of sounds
•Valuable tool for investigating perception
Timing - Voicing
Voice Onset Time (VOT)
60 msec
English VOT production
• Not uniform
• 2 categories
Perceiving VOT
‘Categorical Perception’
Discrimination
Same/Different
0ms 60ms
Same/Different
0ms 10ms
Same/Different
40ms 40ms
A More Systematic Test
D
0ms
20ms
D
D
20ms
40ms
T
T
40ms
60ms
T
Within-Category Discrimination is Hard
Quantifying Sensitivity
Quantifying Sensitivity
• Response bias
• Two measures of discrimination
– Accuracy: how often is the judge correct?
– Sensitivity: how well does the judge distinguish the categories?
• Quantifying sensitivity
– Hits
False Alarms
Misses
Correct Rejections
– Compare p(H) against p(FA)
Quantifying Sensitivity
• Is one of these more impressive?
– p(H) = 0.75, p(FA) = 0.25
– p(H) = 0.95, p(FA) = 0.45
• A measure that amplifies small percentage differences at extremes
z-scores
Normal Distribution
Dispersion
around mean
Standard Deviation
A measure of dispersion
around the mean.
Mean (µ)
√(
∑(x - µ)2
n
)
The Empirical Rule
1 s.d. from mean: 68% of data
2 s.d. from mean: 95% of data
3 s.d. from mean: 99.7% of data
Quantifying Sensitivity
• A z-score is a reexpression of a data point in units of standard
deviations.
(Sometimes also known as standard score)
• In z-score data, µ = 0,  = 1
• Sensitivity score
d’ = z(H) - z(FA)
See Excel worksheet
sensitivity.xls
Quantifying Differences
(Näätänen et al. 1997)
(Aoshima et al. 2004)
(Maye et al. 2002)
Normal Distribution
Dispersion
around mean
Standard Deviation
A measure of dispersion
around the mean.
Mean (µ)
√(
∑(x - µ)2
n
)
The Empirical Rule
1 s.d. from mean: 68% of data
2 s.d. from mean: 95% of data
3 s.d. from mean: 99.7% of data
Normal Distribution
Standard deviation
 = 2.5 inches
Heights of American
Females, aged 18-24
Mean (µ)
65.5 inches
• If we observe 1 individual, how likely is it
that his score is at least 2 s.d. from the
mean?
• Put differently, if we observe somebody
whose score is 2 s.d. or more from the
population mean, how likely is it that the
person is drawn from that population?
• If we observe 2 people, how likely is it that
they both fall 2 s.d. or more from the mean?
• …and if we observe 10 people, how likely
is it that their mean score is 2 s.d. from the
group mean?
• If we do find such a group, they’re probably
from a different population

• Standard Error
is the Standard Deviation of sample means.

n
• If we observe a group whose mean differs
from the population mean by 2 s.e., how
likely is it that this group was drawn from
the same population?
Development of Speech
Perception in Infancy
Voice Onset Time (VOT)
60 msec
Perceiving VOT
‘Categorical Perception’
Discrimination
Same/Different
0ms 60ms
Same/Different
0ms 10ms
Same/Different
40ms 40ms
A More Systematic Test
D
0ms
20ms
D
D
20ms
40ms
T
T
40ms
60ms
T
Within-Category Discrimination is Hard
Cross-language Differences
R
R
L
L
Cross-Language Differences
English vs.
Japanese R-L
Three Classics
Development of Speech Perception
• Unusually well described in past 30 years
• Learning theories exist, and can be tested…
• Jakobson’s suggestion: children add feature contrasts to
their phonological inventory during development
Roman Jakobson, 1896-1982
Kindersprache, Aphasie und allgemeine Lautgesetze, 1941
Developmental Differentiation
Universal
Phonetics
0 months
Native Lg.
Phonetics
6 months
Native Lg.
Phonology
12 months
18 months
#1 - Infant Categorical Perception
Eimas, Siqueland, Jusczyk &
Vigorito, 1971
Discrimination
Same/Different
0ms 60ms
Same/Different
0ms 10ms
Same/Different
40ms 40ms
A More Systematic Test
D
0ms
20ms
D
D
20ms
40ms
T
T
40ms
60ms
T
Within-Category Discrimination is Hard
English VOT Perception
To Test 2-month olds
Not so easy!
High Amplitude
Sucking
Eimas et al. 1971
General Infant Abilities
• Infants’ show Categorical Perception of
speech sounds - at 2 months and earlier
• Discriminate a wide range of speech
contrasts (voicing, place, manner, etc.)
• Discriminate Non-Native speech contrasts
e.g., Japanese babies discriminate r-l
e.g., Canadian babies discriminate d-D
Universal Listeners
• Infants may be able to discriminate all
speech contrasts from the languages of the
world!
How can they do this?
• Innate speech-processing capacity?
• General properties of auditory system?
What About Non-Humans?
• Chinchillas show categorical perception of
voicing contrasts!
#2 - Becoming a Native Listener
Werker & Tees, 1984
When does Change Occur?
• About 10 months
Janet Werker
U. of British Columbia
Conditioned Headturn Procedure
When does Change Occur?
• Hindi and Salish
contrasts tested
on English kids
Janet Werker
U. of British Columbia
Conditioned Headturn Procedure
What do Werker’s results show?
• Is this the beginning of efficient memory
representations (phonological categories)?
• Are the infants learning words?
• Or something else?
Korean has [l] & [r]
[rupi]
“ruby”
[kiri]
“road”
[saram]
“person”
[ir}mi] “name”
[ratio]
“radio”
[mul]
“water”
[pal]
“big”
[s\ul]
“Seoul”
[ilkop]“seven”
[ipalsa]
“barber”
#3 - What, no minimal pairs?
Stager & Werker, 1997
A Learning Theory…
• How do we find out the contrastive phonemes of a
language?
• Minimal Pairs
Word Learning
• Stager &
Werker 1997
‘bih’ vs. ‘dih’
and
‘lif’ vs. ‘neem’
PRETEST
QuickTime™ and a
Video decompressor
are needed to see this picture.
QuickTime™ and a
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QuickTime™ and a
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are needed to see this picture.
HABITUATION
TEST
SAME
SWITCH
Abstraction
• Representations
– Sound encodings - clearly non-symbolic, but otherwise unclear
– Phonetic categories
– Memorized symbols: /k/ /æ/ /t/
• Behaviors
–
–
–
–
Successful discrimination
Unsuccessful discrimination
‘Step-like’ identification functions
Grouping different sounds
Word learning results
• Exp 2 vs 4
Why Yearlings Fail on Minimal
Pairs
• They fail specifically when the task requires
word-learning
• They do know the sounds
• But they fail to use the detail needed for
minimal pairs to store words in memory
• !!??
One-Year Olds Again
• One-year olds know the surface sound
patterns of the language
• One-year olds do not yet know which
sounds are used contrastively in the
language…
• …and which sounds simply reflect
allophonic variation
• One-year olds need to learn contrasts
Maybe not so bad after all...
• Children learn the feature contrasts of their
language
• Children may learn gradually, adding features over
the course of development
• Phonetic knowledge does not entail
phonological knowledge
Roman Jakobson, 1896-1982
Werker et al. 2002
14
17
20
Swingley & Aslin, 2002
• 14-month olds did recognize mispronunciations of familiar
words
Alternatives to Reviving Jakobson
• Word-learning is very hard for younger children, so detail
is initially missed when they first learn words
• Many exposures are needed to learn detailed word forms at
early stages of word-learning
• Success on the Werker/Stager task seems to be related to
the vocabulary spurt, rapid growth in vocabulary after ~50
words
Questions about Development
6-12 Months: What Changes?
Structure Changing
Patricia Kuhl
U. of Washington
Structure Adding
• Evidence for Structure Adding
(i) Some discrimination retained when sounds presented
close together (e.g. Hindi d-D contrast)
(ii) Discrimination abilities better when people hear sounds
as non-speech
(iii) Adults do better than 1-year olds on some sound
contrasts
• Evidence for Structure Changing
(i) No evidence of preserved non-native category
boundaries in vowel perception
Sources of Evidence
• Structure-changing: mostly from vowels
• Structure-adding: mostly from consonants
• Conjecture: structure-adding is correct in domains where
there are natural articulatory (or acoustic) boundaries
So how do infants learn…?
• Surface phonetic patterns
• Tests of experimentally induced changes…
5 hours’ exposure to Mandarin
± human interaction
[2003, Proceedings of the National Academy of Sciences]
Jessica Maye, Northwestern U.
• Infants at age 6-8 months are still ‘universal listeners’, cf.
Pegg & Werker (1997)
• Infants trained on bi-modal distribution show ‘novelty
preference’ for test sequence with fully alternating
sequence
• How could the proposal scale up?
Invariance
(Jusczyk 1997)
Training on [g-k] or [d-t], generalization across place of articulation.
(Dis-)habituation paradigm.
[Maye & Weiss, 2003]
So how do infants learn…?
• Phoneme categories and alternations
– Perhaps more like a phonologist than like a LING101
student - look directly for systematic relations among
phones
– Gradual articulation of contrastive information encoded
in lexical entries
– Much remains to be understood
Abstraction in Infant Speech Encoding
• From a very early age infants show great sensitivity to speech sounds,
possibly already with some category-like structure
• Although native-like sensitivity develops early (< 1 year), this should
be distinguished from adult-like knowledge of the sound system of the
language
– Children still need to learn how to efficiently encode words (phoneme
inventory)
– Children presumably still need to learn how to map stored word forms
onto pronunciations (phonological system of the language)
• Popular distributional approaches to learning the sound system address
rather non-abstract encodings of sounds, at best