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Categorical perception of speech: Task variations in infants and adults

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Categorical perception of speech: Task variations in infants and adults Bob McMurray Jessica Maye Andrea Lathrop and Richard N. Aslin And a big thanks to Julie Markant – PowerPoint PPT presentation

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Title: Categorical perception of speech: Task variations in infants and adults


1
Categorical perception of speech Task variations
in infants and adults
Bob McMurray Jessica Maye Andrea
Lathrop and Richard N. Aslin
And a big thanks to Julie Markant
2
Categorical Perception Task Variations
  • Overview
  • Previous work
  • Categorical perception and gradient sensitivity
    to subphonemic detail.
  • Categorical perception in infants
  • Reassessing this with HTPP AEM
  • Infants show gradient sensitivity
  • A new methodology
  • Adult analogues

3
Categorical Perception
Categorical Perception Is subphonemic detail
retained and used during speech perception?
For a long time NO! Subphonemic variation is
discarded in favor of a discrete label.
Categorical perception gradiency
4
Non-categorical Perception
A number of psychophysical-type results showed
listeners sensitivity to within-category
detail. 4AIX Task Pisoni Lazarus
(1974) Speeded Response Carney, Widen
Viemeister (1977) Training Samuel
(1977) Pisoni, Aslin, Henessey Perey
(1982) Rating Task Miller (1997) Massaro
Cohen (1983)
5
Word Recognition
These results did not reveal
Whether on-line word recognition is sensitive to
such detail. Whether such sensitivity is useful
during recognition.
6
Word Recognition
  • Mounting evidence that word-recognition is
    sensitive
  • Lahiri Marslen-Wilson (1991) vowel
    nasalization
  • Andruski, Blumstein Burton (1994) VOT
  • Gow Gordon (1995) word segmentation
  • Salverda, Dahan McQueen (in press) embedded
    words and vowel length.
  • Dahan, Magnuson, Tanenhaus Hogan (2001)
    coarticulatory cues in vowel.

7
Gradient Sensitivity
McMurray, Tanenhaus Aslin (2002)
Bear
8
Gradient Sensitivity
This systematic, gradient relationship between
lexical activation and acoustic detail would
allow the system take advantage of fine-grained
regularities in the signal.
  • Gow, McMurray Tanenhaus (Sat., 600 poster
    session)
  • Anticipate upcoming material.
  • Resolve Ambiguity

9
Infant categorical perception
c
Early findings of categorical perception for
infants (e.g. Eimas, Siqueland, Jusczyk
Vigorito) have never been refuted. Most studies
use Habituation (many repetitions) Synthetic
Speech Single continuum Perhaps a different
method would be more sensitive?
Categorical perception in infants
10
Head-Turn Preference Procedure
  • Jusczyk Aslin (1995)
  • Infants exposed to a chunk of language
  • Words in running speech.
  • Stream of continuous speech (ala stat. learning)
  • Word list
  • After exposure, memory for exposed items (or
    abstractions) is assessed by comparing listening
    time to consistent items with inconsistent items.

11
How do we measure listening time?
After exposure Center Light blinks. Brings
infants attention to center.
12
How do we measure listening time?
When infant looks at center One of the
side-lights blinks.
13
How do we measure listening time?
When infant looks at side-light she hears a
word.
14
How do we measure listening time?
When infant looks at side-light she hears a
word. as long as she keeps looking
15
Experiment 1 Gradiency in Infants
c
7.5 month old infants exposed to either 4 b-, or
4 p-words Bomb Bear Bail Beach Palm Pear Pail
Peach 80 repetitions total Form a category of
the exposed class of words.
Infants show gradient sensitivity
Measure listening time on Bear Pear (Original
word) Pear Bear (opposite) Bear Pear (VOT
closer to boundary).
16
Experiment 1 Stimuli
Stimuli constructed by cross-splicing natural,
recorded tokens of each end point.
17
Measuring gradient sensitivity
Looking time is an indication of interest. After
hearing all of those B-words P sounds pretty
interesting. So infants should look longer for
pear than bear.
What about in between?
18
Individual Differences
Novelty/Familiarity preference varies across
infants and experiments. Were only interested
in the middle stimuli (b, p). Infants
categorized as novelty or familiarity preferring
by performance on the endpoints.
Novelty Familiarity
B 27 11
P 19 10
Within each group will we see evidence for
gradiency?
19
Novelty Results
Novelty infants, Trained on B VOT p.001 Lin
ear Trend p.001
.14
.004
20
Novelty Results
Novelty infants, Trained on P VOT p.001 Lin
ear Trend p.001
21
Familiarity Results
Familiarity infants showed similar effects. B
exposure Trend p.001 B vs B p.19 B vs
P p.21 P exposure Trend p.009 P vs P
p.057 P vs. B p.096
Trained on B
Trained on P
22
Experiment 1 Conclusions
  • 7.5 month old infants show gradient sensitivity
    to subphonemic detail.
  • Individual differences in familiarity/novelty
    preferences. Why?
  • Length of exposure?
  • Individual factors?
  • Limitations of paradigm may hinder further study
  • More repeated measures
  • Better understanding of task
  • Wider age-range.

23
Anticipatory Eye-Movements
An ideal methodology would Yield an arbitrary,
identification response. Yield a response to a
single stimuli Yield many repeated measures Much
like a forced-choice identification
A new methodology
Anticipatory Eye-Movements (AEM) Train Infants
to look left or right in response to a single
auditory stimulus
24
Anticipatory Eye-Movements
Visual stimulus moves under occluder. Reemergence
serves as reinforcer Concurrent auditory
stimulus predicts endpoint of occluded
trajectory. Subjects make anticipatory
eye-movements to the expected locationbefore the
stimulus appears.
Teak
Lamb
25
Anticipatory Eye-Movements
After training on original stimuli, infants are
tested on a mixture of
  • original, trained stimuli (reinforced)
  • Maintain interest in experiment.
  • Provide objective criterion for inclusion
  • new, generalization stimuli (unreinforced)
  • Examine category structure/similarity relative
    to trained stimuli.

26
Experiment 2 Pitch and Duration
Goals Use AEM to assess auditory
categorization. Assess infants abilities to
normalize for variations in pitch and
duration or Are infants sensitive to
acoustic-detail during a lexical identification
task...
27
Experiment 2 Pitch and Duration
Training Teak -gt rightward trajectory. Lamb
-gt leftward trajectory.
Test Lamb Teak with changes in Duration 33
and 66 longer. Pitch 20 and 40 higher
If infants ignore irrelevant variation in pitch
or duration, performance should be good for
generalization stimuli. If infants lexical
representations are sensitive to this variation,
performance will degrade.
28
The Stimuli
Training stimulus
29
The Stimuli
Testing stimulus
30
Results
Each trials is scored as correct longer
looking time to the correct side. incorrect
longer looking time to incorrect side. Binary
DVsimilar to 2AFC.
On trained stimuli 11 of 29 infants performed
better than chancethis is a tough tasks for
infants. Perhaps more training.
31
Results
On generalization stimuli
Proportion Correct Trials
Duration
Pitch
Training Stimuli
D1 / P1
D2 / P2
Stimulus
32
Experiment 2 Conclusions
Infants developing lexical categories show
graded sensitive to variation in duration.
Possibly not to pitch Might be an effect of
task relevance AEM yields more repeated
measurements better understood task 2AFC Could
it yield a picture of the entire developmental
time course? Is AEM applicable to a wider age
range?
33
Treating undergraduates like babies
Extreme case Adult perception.
Adults generally wont Look at blinking
lights Suck on pacifiers Kick their feet at
mobiles
Result few infant methodologies allow direct
analogues to adults. They do make
eye-movements could AEM be adapted?
34
Treating undergraduates like babies
Pilot study. 5 adults exposed to AEM
stimuli. Training Ba left Pa right Test
Ba Pa (0-40 ms) VOT continuum.
35
Results
1
0.9
0.8
0.7
0.6
2AFC
/p/
0.5
AEM
0.4
0.3
0.2
0.1
0
0
5
10
15
20
25
30
35
40
VOT (ms)
36
Adult AEM Conclusions
AEM paradigm can be used unchanged for
adults. Should work with older children as
well. Results show same category boundary as
traditional 2AFC tasks, perhaps more sensitivity
to fine-grained acoustic detail. Potentially
useful for speech categorization when categories
are not nameable pictureable immediately
obvious
37
Conclusions
Like adults,7.5-month-old infants show gradient
sensitivity to subphonemic detail. VOT Duration
Perhaps not pitch (w.r.t. lexical categories)
38
Conclusions
Task makes the difference Moving to HTPP from
habituation revealed subphonemic
sensitivity. Taking into account individual
differences crucial. Moving to AEM
yields Better ability to examine tuning over
time. Ability to assess perception across
lifespan with a single paradigm.
39
Categorical perception of speech Task variations
in infants and adults
Bob McMurray Jessica Maye Andrea
Lathrop and Richard N. Aslin
And a big thanks to Julie Markant
40
Natural Stimuli
Infants may show more sensitivity to natural
speech Stimuli constructed from natural tokens
of actual words with progressive cross-splicing.
41
Experiment 1 Reprise
Difficult to examine how sensitivity might be
tuned to environmental factors in
head-turn-preference procedure.
  • High variance/individual differencescant
    predict novelty/familiarity.
  • Only a single point to look at.
  • Between-subject comparison.
  • Difficult interaction to obtain

Bear
Bear
Pear
42
Experiment 1 Reprise
AEM presents a potential solution 1) Looking at
whole continuum would yield more power.
Bear
Pear
2) Is AEM applicable to a wider age range?
43
The Stimuli
Training stimulus
44
Data analysis
Data coded by naive coders from video containing
pupil scene monitors.
45
Data analysis
Eye-movements coded from maximal size of
stimulus to first appearance (or end of trial).
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