RealTime Dynamics of Language Acquisition in TwoYearOld Children and Connectionist Models

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Real-Time Dynamics of Language Acquisition in
Two-Year-Old Children and Connectionist Models
Jessica S. Horst (jessica-horst_at_uiowa.edu) Larissa
K. Samuelson (larissa-samuelson_at_uiowa.edu) Bob
McMurray (bob-mcmurray_at_uiowa.edu) Dept. of
Psychology University of Iowa
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Word Learning

• Children are amazing word learners
• By 5th birthday know 60,000 words
• Estimated to learn 9 words/day from 18mo (Carey,
  1978)
• Big Question What it takes to turn a novel name
  into a known name?

Teddy
Puppy
?
Bunny
Kitty
Doll
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Fast Mapping

• Linking a novel name to a novel referent with
  minimal exposure (Carey Bartlett, 1978)
• Literature associates amazing word learning with
  fast mapping
• Children can fast map several names in a single
  session (Golinkoff et al., 1992)
• Children can determine the referent of a novel
  name in less than 3 seconds (Halberda, submitted)
• Big Picture Understanding the processes of word
  learning, by determining exactly what children
  are learning about name-object mappings taught
  with minimal exposure

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Two Times Scales in Language Acquisition
Fast Mapping and Word Learning represent two time
scales of learning
Rabbit

• Fast Mapping quick process emerging in the
  moment
• Based on the Principle of Lexical Contrast
  (Clark, 1987)

Rabbit?
Rabbit?
Rabbit?
Kitty ? Rabbit
Puppy ? Rabbit
This must be Rabbit
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• Word Learning gradual process over the course of
  development
• Evidenced by production or identification of the
  referent after a delay

Next week, were going to see Sallys Rabbit. She
might let you pet the Rabbit. The Rabbit is very
soft, but you must be very gentle with the
Rabbit.
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Question Is Lexical Contrast enough to truly
learn a word, i.e., to show evidence of learning
after a delay?
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General Methods

• Fast mapping trials
• 2 familiar objects
• 1 novel object

Cow (familiar)
Block (familiar)
Yok (novel)
Child is asked for both familiar (cow) and novel
(fode) objects across trials
Five-minute delay period

• Retention trials
• 1 target
• 1 prev. named novel
• 1 prev. unnamed novel

Tannin (named foil)
Yok (target)
unnamed foil (previously seen)
3 warm-up trials with 3 familiar objects are
presented before the FM trials. 1 additional
warm-up trial is presented before the retention
trials.
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Experiment 1

• 24-month-old children (N 16)
• 2 familiar 1 novel objects
• 8 familiar and 8 novel trials (e.g., get the
  cow! or get the yok!)

1
p lt .001

0.8

0.6
Proportion of Correct Choices
0.4
Chance
0.2
0
Familiar Names
Novel Names
Retention
Children were excellent at fast mapping (finding
the referent of novel and familiar words in the
moment). Children were unable to show evidence of
retention after a five-minute delay. Note only
tested correctly fast mapped names for retention
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Did Children Learn Individual Words?
Retention Data
1
0.8
0.6
0.4
Chance
Proportion of Correct Choices
0.2
0
Names 3 4
Names 5 6
Names 7 8
Names 1 2

• What if children may retain 1, but not as many as
  8 names?
• names were analyzed by order of presentation
  during fast mapping
• none of the positions above chance levels
• Children unable to retain mappings after a
  5-minute delay

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Experiments 2 and 3

• Initial findings replicated with simpler tasks
• effect of number of names or trials?
• Childrens difficulty in retaining newly
  fast-mapped names is not related to the number of
  names or trials

Replication 1 (E2) (N 16)
Replication 2 (E3) (N 16)

• 1 Novel Name
• 8 Familiar Names
• 7 Preference Trials

• 1 Novel Name
• 2 Familiar Names

Expected by chance 3.33
Expected by chance 2.67
Expected by chance 5.33
Expected by chance 5.33
Binomial, p lt .05, Binomial, p .12
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The Model
Decision Units

• 15 Auditory 15 Visual units
• Activate according to what child sees and hears
• 90 Decision units
• Names presented singly with a variable number of
  objects

Visual Units
Auditory Units
Decision Units

• Name-Decision Object-Decision associations
  strengthened via learning
• After 4000 training trials network forms localist
  representations
• Learns name-object links and to ignore visual
  competitors

Visual Units
Auditory Units
End State Post Learning
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Processing In The Model

• Activation feeds from input layers to decision
  layers.
• Decision units compete via inhibition.
• Activation feeds back to input layers.
• Cycle continues until system settles.

Decision Units (Hidden) Layer
Auditory Inputs
Visual Inputs
(McMurray Spivey, 2000)

• Unsupervised Hebbian learning occurs on every
  cycle.

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• Online decision dynamics reflect auditory and
  visual competitors.

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Connection Strength
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• 20 networks initialized with random weights
• 15 word lexicon (names objects)
• Familiarization with Initial Vocabulary
• Familiarized with 5 familiar items for 5000
  epochs
• Items presented in random order
• Fast Mapping Experiment

• 5 familiar names
• 5 novel names
• 5 held out

• 5 retention trials

• 10 fast mapping trials

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Fast Mapping In The Model

• Model succeeded on both types of fast-mapping
  trials
• Model behavior patterned with empirical results
• Learning was not turned of during fast mapping

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Retention In The Model

• The model fails to retain the newly learned
  words after a delay
• Learning was not turned of during retention

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Why Didnt The Simulations Retain?

• Analyses of weight matrices revealed that
  relatively little learning occurred during fast
  mapping trials.

Change (RMS) in portions of weight matrix
2
1.6
1.2
Squared Deviations
0.8
0.4
0
Familiar
Familiar
Novel
Control
Words
Words
Words
Words
After
After Test
End
End
Learning
Temporal dynamics of processing
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Implications

• Making the name-object mapping in the moment is
  not enough to form a long-term memory
  representation of the novel name
• Lexical Contrast provided in 1 fast mapping trial
  not sufficient to turn a novel name into a known
  name
• Goal for Experiment 4
• Add more support to the task to facilitate word
  learning
• Increase the number of naming instances (see
  Merriman Marazita,1995)
• Provide reinforcement
• Provide ostensive naming (see Mervis Bertrand,
  1994)

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Methods

• Two conditions reinforced and ostensive
  definition
• All children heard the names 5 times before each
  trial
• Can you get the yok? Help me find the yok! Are
  you ready to find the yok? Can you help me get
  the yok? Lets get the yok!

Reinforced Condition Yes, that is the yok
(Child holding) Ostensive Naming Look, this is
the yok (Exptr holding Target pointing)
Reinforced Condition That is the cow. (Child
holding) Ostensive Naming Look, this is the
yok (Exptr holding Target pointing)
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Experiment 4
p lt .001
1

Retention


Ostensive Definition

0.8
0.6
Proportion of Correct Choices
0.4
chance
0.2
0
Familiar Names
Novel Names
Retention

• Again, children were excellent at fast mapping
• Overall, however, they were very poor at
  retaining
• No effects of Condition were found for fast
  mapping
• Note only tested correctly fast mapped names
  for retention

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p lt .05

• When analyzed by block, it is clear that children
  retained names in the Ostensive Definition
  Condition
• Data suggests children can learn up to 4 names in
  this task
• Analysis of looking indicated that children
  attended to novel object twice as much in OD
  condition

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Conclusions

• Overall, children were excellent at finding the
  referent in the moment, but unable to retain the
  names over a five-minute delay (E1)
• Follow-up experiments indicate poor retention not
  due to
• The number of names introduced (E2) or
• The number of trials in the session (E3)
• The Connectionist Network captured the data and
• Showed the same pattern of results
• excellent Fast Mapping, poor Retention
• Learning was occurring during fast mapping, but
  not enough learning to support later evidence of
  retention

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• Together, Experiments 1 - 3 and Simulations
  suggest that Lexical Contrast alone is not enough
  to allow children to form a strong enough
  representation of a novel name to show evidence
  of word learning after five minutes
• Children are able to retain words taught in a
  Fast Mapping Task if
• Provided with multiple naming instances
• And ostensive definitions (E4)
• But only able to learn up to 4 words
• Future research will explore the role of
  attention in helping children turn novel names
  into known names

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Take Home Message
Fast Mapping is a quick, online mechanism that
can produce smart online behavior but not actual
word learning.
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References

• Carey, S. (1978). The child as word learner. In
  M. Halle, J. Bresnan A. Miller (Eds.),
  Linguistic Theory and Psychological Reality (pp.
  264-293). Cambridge, MA MIT Press.
• Carey, S., Bartlett, E. (1978). Acquiring a
  single new word. Proceedings of the Stanford
  Child Language Conference, 15(17-29).
• Clark, E. (1987). The Principle of Contrast A
  Constraint on Language Acquisition. In B.
  McWhinney (Ed.), Mechanisms of Language
  Acquisition (pp. 1-33). Hillsdale, NJ Lawrence
  Erlbaum Associates Inc.
• Golinkoff, R. M., Hirshpasek, K., Bailey, L. M.,
  Wenger, N. R. (1992). Young-Children and Adults
  Use Lexical Principles to Learn New Nouns.
  Developmental Psychology, 28(1), 99-108.
• Halberda, J. Goldman, J. (submitted). One Trial
  Learning in 2-Year-Olds Children Learn New Nouns
  in 3 Seconds Flat.
• Mervis, C. B., Bertrand, J. (1994). Acquisition
  of the Novel Name Nameless Category (N3c)
  Principle. Child Development, 65(6), 1646-1662
• Merriman, W. E. Marazita, J. M. (1995). The
  Effect of Hearing Similar Sounding Words on Young
  2-Year-Olds Disambiguation of Novel Reference.
  Developmental Psychology, 31(6), 973-984.
• McMurray, B., Spivey, M. (2000). The
  Categorical Perception of Consonants The
  Interaction of Learning and Processing, The
  Proceedings of the Chicago Linguistics Society,
  34(2), 205-220.

Acknowledgements
The authors would like to thank Joseph Toscano
for programming assistance and support. This
work was supported by NICHD Grant R01-HD045713 to
LKS.