An Eye-Tracking Study of Receptive Verb Knowledge in Toddlers

Purpose

We examined receptive verb knowledge in 22- to 24-month-old toddlers with a dynamic video eye-tracking test. The primary goal of the study was to examine the utility of eye-gaze measures that are commonly used to study noun knowledge for studying verb knowledge.

Method

Forty typically developing toddlers participated. They viewed 2 videos side by side (e.g., girl clapping, same girl stretching) and were asked to find one of them (e.g., "Where is she clapping?"). Their eye-gaze, recorded by a Tobii T60XL eye-tracking system, was analyzed as a measure of their knowledge of the verb meanings. Noun trials were included as controls. We examined correlations between eye-gaze measures and score on the MacArthur–Bates Communicative Development Inventories (CDI; Fenson et al., 1994), a standard parent report measure of expressive vocabulary to see how well various eye-gaze measures predicted CDI score.

Results

A common measure of knowledge—a 15% increase in looking time to the target video from a baseline phase to the test phase—did correlate with CDI score but operationalized differently for verbs than for nouns. A 2nd common measure, latency of 1st look to the target, correlated with CDI score for nouns, as in previous work, but did not for verbs. A 3rd measure, fixation density, correlated for both nouns and verbs, although the correlation went in different directions.

Conclusions

The dynamic nature of videos depicting verb knowledge results in differences in eye-gaze as compared to static images depicting nouns. An eye-tracking assessment of verb knowledge is worthwhile to develop. However, the particular dependent measures used may be different than those used for static images and nouns.

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