real-time dynamics of language acquisition in two-year-old 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 ([email protected]) Larissa K. Samuelson ([email protected]) Bob McMurray ([email protected]) Dept. of Psychology University of Iowa. Word Learning. - PowerPoint PPT PresentationTRANSCRIPT
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Real-Time Dynamics of Language Acquisition in Two-Year-Old Children
and Connectionist Models
Jessica S. Horst ([email protected])Larissa K. Samuelson ([email protected])Bob McMurray ([email protected])
Dept. of PsychologyUniversity of Iowa
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Word LearningChildren 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?
“Puppy”
“Kitty”“Doll”
“Teddy”
“?” “Bunny”
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Fast MappingLinking 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 AcquisitionFast Mapping and Word Learning represent two time scales of learning:
Fast Mapping: quick process emerging in the moment
• Based on the Principle of Lexical Contrast (Clark, 1987)
Rabbit
“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, we’re going to see Sally’s Rabbit. She might let you pet the Rabbit. The Rabbit is very soft, but you must be very gentle with the Rabbit….
My Picture Book
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 MethodsFast mapping trials:• 2 familiar objects • 1 novel object
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.
Cow (familiar) Block (familiar) Yok (novel)
Retention trials: •1 target•1 prev. named novel•1 prev. unnamed
novel
Child is asked for both familiar (cow) and novel (fode) objects across trials
Five-minute delay period
Yok(target)
Tannin (named foil)
unnamed foil(previously seen)
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24-month-old children (N = 16)2 familiar & 1 novel objects8 familiar and 8 novel trials (e.g., “get the cow!” or “get the yok!”)
Experiment 1:
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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Familiar Names Novel Names RetentionPr
opor
tion
of C
orre
ct C
hoic
es
Chance
******
*** p < .001
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Did Children Learn Individual Words?
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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Names 1 & 2
Prop
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Cor
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Cho
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Names 3 & 4 Names 5 & 6 Names 7 & 8
Chance
Retention Data
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• Initial findings replicated with simpler tasks:• effect of number of names or trials?
• Children’s difficulty in retaining newly fast-mapped names is not related to the number of names or trials
Experiments 2 and 3
Fast Mapping Retention
10/16* 4/10
Fast Mapping Retention
8/16† 3/8
* Binomial, p < .05, † Binomial, p = .12
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: 2.67Expected by chance: 5.33 Expected by chance: 5.33
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The Model
End StatePost Learning
Intermediate StateDuring Learning
•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
•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
Decision Units
Decision Units
Aud
itory
Uni
ts
Aud
itory
Uni
ts Visual U
nitsV
isual Units
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• Activation feeds from input layers to decision layers.
• Decision units compete via inhibition.
• Activation feeds back to input layers.
• Cycle continues until system settles.
Processing In The Model
(McMurray & Spivey, 2000)
• Unsupervised Hebbian learning occurs on every cycle.
Decision Units (Hidden) Layer
Auditory Inputs
Visual Inputs
“fork”
“spoon”
“cup”
“plate”
“knife”
“napkin”
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• Online decision dynamics reflect auditory and visual competitors.
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Cycles
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Aud
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Inpu
t
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10Decision Units
10 20 30 40 50 60 70 80 90A
udito
ry In
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Decision Units10 20 30 40 50 60 70 80 90
9 16 26 30 32 39 41 49 6567
0.05
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Con
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Stre
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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 orderFast Mapping Experiment:
• 5 familiar names• 5 novel names• 5 held out
• 5 retention trials• 10 fast mapping trials
familiar
novel
held out
cup
“Fode”
ball
fode“Yok” yok
fode
???
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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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Familiar Name Novel Name
Prop
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Cho
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******
Chance
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• The model fails to “retain” the newly learned words after a “delay”
• Learning was not turned of during retention
Chance
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Familiar Name Novel Name Retention
Prop
ortio
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ices
*** ***
Retention In The Model
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Why Didn’t The Simulations Retain?• Analyses of weight matrices revealed that relatively little
learning occurred during fast mapping trials.
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Cycles (novel words)0 5 10 15 20
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FamiliarWords
FamiliarWords
NovelWords
ControlWords
AfterLearning
After Test
Squa
red
Dev
iatio
ns
Change (RMS) in portions of weight matrix
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0.000001
0.000002
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0.000005
Familiar Words Novel Words Control Words
After TestSq
uare
d D
evia
tions
Temporal dynamics of processing
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1 4 80 8666
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Prio
r to
Expe
rimen
t10 20 30 40 50 60 70 80 90
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erim
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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? Let’s get the yok!”
Reinforced Condition: “Yes, that is the yok” (Child holding)Ostensive Naming: “Look, this is the yok” (Exptr holding Target & pointing)
Correct choice: Incorrect choice:
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:
• 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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Familiar Names Novel Names Retention
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Ostensive Definition****** ***
***
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chance
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• 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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Block 1 Block 2 Block 3 Block 4
Prop
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Ostensive Definition
**
* p < .05
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• 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
Conclusions
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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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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.
References
AcknowledgementsThe authors would like to thank Joseph Toscano for programming assistance and support.
This work was supported by NICHD Grant R01-HD045713 to LKS.