Fast mapping, slow learning: disambiguation of novel word-object mappings in relation to vocabulary learning at 18, 24, and 30months

Abstract

When hearing a novel name, children tend to select a novel object rather than a familiar one, a bias known as disambiguation. Using online processing measures with 18-, 24-, and 30-month-olds, we investigate how the development of this bias relates to word learning. Children's proportion of looking time to a novel object after hearing a novel name related to their success in retention of the novel word, and also to their vocabulary size. However, skill in disambiguation and retention of novel words developed gradually: 18-month-olds did not show a reliable preference for the novel object after labeling; 24-month-olds reliably looked at a novel object on Disambiguation trials but showed no evidence of retention; and 30-month-olds succeeded on Disambiguation trials and showed only fragile evidence of retention. We conclude that the ability to find the referent of a novel word in ambiguous contexts is a skill that improves from 18 to 30months of age. Word learning is characterized as an incremental process that is related to - but not dependent on - the emergence of disambiguation biases.

Figure 1.

Trial types in Experiments 1 and 2. Six familiar objects and two novel objects were used as visual stimuli in each experiment.

Figure 2.

Overall accuracy of responses on Familiar-word and Retention trials by children at 18 months of age in Experiment 1. Curves show the mean proportion of trials on which children were fixating the target picture at each 33-ms interval as the stimulus sentence unfolded, measured from acoustic onset of the noun. The first vertical dashed line indicates 300-ms after noun onset, and the second marks the mean noun offset (785 ms). The horizontal line represents .50, the chance level of proportion of looking time to the correct picture. Error bars indicate standard errors from the means and are graphed every 400-ms. When novel words were taught ostensively, 18-month-olds retained the mappings between novel words and novel objects.

Figure 3:

Overall accuracy of responses on Familiar-word, Disambiguation, and Retention trials, by children at 18, 24, and 30 months of age. Curves show the mean proportion of trials on which children were fixating the target picture at each 33-ms interval as the stimulus sentence unfolded, measured from the acoustic onset of the noun. Error bars indicate standard errors from the means and are graphed every 400-ms. In all age groups, children were above chance on Familiar-word trials. At 18 and 24 months, children were above chance on Disambiguation trials. Only at 30 months were children above chance on Retention trials.

Figure 4:

Mean accuracy on Familiar-word, Disambiguation, and Retention trials, for the three age groups. Error bars represent standard errors of the mean over participants. Children were more accurate on Familiar-word than on Disambiguation trials, and more accurate on Disambiguation than on Retention trials, and they made comparable gains with age across conditions.

Figure 5:

Correlation between accuracy on Disambiguation trials and accuracy on Retention trials at 18, 24, and 30 months of age. Across age groups, children with higher accuracy on Disambiguation trials were better at remembering the mapping between the novel word and the novel object on Retention trials.

Figure 6:

Correlations between accuracy on Disambiguation trials and productive vocabulary (CDI) at 18, 24, and 30 months of age. Children with higher vocabularies spent a greater proportion of time looking at the novel object after hearing a novel label.