1) The logical inference DisjunctiveSyllogism underlies the word-learningstrategy Mutual Exclusivity.

2) Two-year-olds can learn new nounsgiven a single exposure to a spoken labelin an ambiguous labeling context, devoidof social cues, that lasts only 3 seconds.

ABSTRACTThis Experiment revealed two

important findings:

Two-Year-Olds Fast-mapping of Novel Labels:

How Fast is Fast?Justin HalberdaHarvard University

poster presented at SRCD 2003, Tampa Bay Fl.

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A B

Disjunctive Syllogism

“Point at the dax.”• The name “dax” either refers to A or B• “Dax” does not refer to A (because A iscalled “brush”)

• Therefore, “dax” must refer to B

Mutual ExclusivityContrastPragmatic Account

Consistent with: Novel-Name Nameless-Category

Not consistent with:

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Participants: 20 children (10 boys),mean age: 30-0

Children observed two monitors whichpresented pictures of known and novelobjects (Fig.1). Objects appearedsimultaneously. A speech stimulusasked children to point to one of thetwo objects, “Point at the DAX.”Comprehension was measured asincreased looking and correct pointingto the labeled object.

METHODAn extension of Halberda (2003).

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DESIGN25 total trials

12 known/known trials (e.g. BALL vs. CUP)

12 known/novel trials (e.g. BRUSH vs. DAX)On 6 of these trials the novel object (DAX)

was the labeled target.

Children’s looking to each object (target and

distracter) was analyzed frame by framerevealing the pattern of fixations that led

to success.

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RESULTSDisjunctive Syllogism

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• Children showed a significant tendencyto “double-check” the familiar objectdistractor (e.g. brush) on novel labeltrials (e.g. “dax”) compared to knownlabel trials (e.g. “ball”) consistent withthe possibility that children arereasoning:

A or B Therefore, B

Not A

A

B

Disjunctive Syllogism

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• Also, there is a significant Trial Type XObject Fixated interaction for subjects’Reaction Time to Point to the Target.

• For deciding which object is a “Ball,” therate-limiting information to decide to point isin the Target object . Point times arefaster for Target-fixated trials then forDistractor-fixated.

• For deciding what is a “Dax,” the rate-limiting information is in the Distractorobject . Point times are faster forDistractor-fixated trials then for Target-fixated trials.

• These inferences are also supported bydetailed RT data from adult subjects(Halberda, submitted).

Disjunctive Syllogism

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The last trial that children saw wasidentical to all other trials. But, itpresented children with two novel objects,the names of which they had had a single 3second opportunity to learn earlier in thestudy. Children were given no feed-backas to the correct referent on any trials.

RESULTSFast-Mapping

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Fast-Mapping

Chanceis 50%

100

50

0

The Number of Children Pointing to the Correct Object

Chanceis 50%

100

50

0

Children correctly pointed to the noveltarget indicating that they had learned thename of at least one of the novel objectsduring the course of the study.

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• Children’s eye-movements appear tocorrelate with the inferential steps ofDisjunctive Syllogism (A or B, Not A,Therefore B)

• The relative ordering of point timesalso reflects the use of this strategy.

• 2-3 year-old children are able tolearn a new noun given only a single 3second exposure to the noun andobject in a completely ambiguouslabeling situation.

•Fast-mapping is Fast.

CONCLUSIONS

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REFERENCESHalberda, J. (2003). The development of

a word-learning strategy. Cognition 87, pg B23-B34.

Halberda, J. (submitted). Is this a dax Isee before me? Disjunctive Syllogism support a word-learningstrategy.

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