This study explored infants’ sensitivity to speaker reliability in verb labeling. Past research has focused primarily on nouns (Koenig & Echols, 2003). The participants in this study were 32 24-month-old infants. Visual stimuli included a group of intransitive verbs that should be familiar to 24-month-olds such as jumping, turning, and waving. These stimuli were shown on a television display. Half of the participants were in a True Labeling Condition, in which they heard labels that correctly matched the familiar actions. The other half of the participants were in a False Labeling Condition, in which they heard familiar labels that did not correspond with the familiar actions they saw. The amounts of time that infants looked at action, labeler, and parent were compared across true and false conditions using t-tests. I expected to find that infants have similar expectations about how labels map to referents for verbs and for nouns, such that they expect speakers to apply consistent labels to both. As a result, infants were expected to look longer to the “false” than “true” labeler. Contrary to predictions, infants failed to look longer at the action in the true condition than the false, or to the speaker in the false condition as compared to the true. The comprehensive results for the studies did not indicate that infants expect accurate labels for actions from humans who are intending to refer, as did previous research with objects. / text

The growth of a child’s early vocabulary is one of the most salient indicators of progress in language development, but measuring a young child’s comprehension of words is non-trivial. Parental checklists are prone to underestimation of a child’s vocabulary (Houston-Price et al., 2007; Brady et al. 2014), so it may be that more direct measures, such as measuring a child’s eye movements during comprehension, may provide a better assessment of children’s vocabulary. Prior research has found relationships between gaze patterns and vocabulary development (Fernald et al. 2006), and the present exploratory study investigates these relationships with verbs, along with a number of methodological considerations. In addition, recent research supports the idea that verbs may differ in difficulty of acquisition based on word class, with manner verbs being easier to learn than result verbs (Horvath et al. 2015). The present study has two aims: 1) investigate the effect of dynamic stimuli on correlations with vocabulary scores and 2) experimentally investigate the notion that manner verbs are easier to learn than result verbs. Forty children (Mean age = 22.97 months) were recruited for participation and shown a vocabulary test. While no significant correlations were found between vocabulary measures and accuracy and latency, several experimental measures proved to be related to vocabulary development, including fixation density and length of first fixation to the non-target. Additionally, results indicate that children knew the same number of manner and result verbs. Finally, these results could inform vocabulary tests using eye-tracking measures that specifically target verb knowledge.

Verbs and prepositions encode relations within events, such as a child running towards the top of a hill or a second child pushing the first away from the top. These relational terms present significant challenges in language acquisition, requiring the mapping of the categorical system of language onto the continuous stream of information in events. This challenge is magnified when considering the complexities of events themselves. Events consist of part-whole relations, or partonomic hierarchies, in which events defined by smaller boundaries, such as the child running up the hill, can be integrated into broader categories, such as the second child preventing the first from reaching the top (Zacks & Tversky, 2001). This dissertation addresses how this partonomic hierarchy in events is paralleled in the structure of relational language. I examine the semantic category of force dynamics, or "how entities interact with respect to force" (Talmy, 1988, p. 49), which introduces broad categories (e.g., help, prevent) that incorporate previously independent relations in events, such as paths, goals, and causality. Two studies ask how children and adults navigate the tension between fine and broad categories in their nonlinguistic representations of force and motion events and whether language - in the form of both labels and syntactic cues - helps children to integrate previously independent relations into these higher order constructs. Participants completed a novel task designed to assess the saliency of force dynamics relations across events. Participants viewed an animated event depicting a force dynamics relation (e.g., prevent, cause) and were asked to identify which of two perceptually varied events (i.e., different characters and setting) depicted the same relation. Study One extends previous research, showing that adults encode force dynamics relations in nonlinguistic contexts. Study Two examined these representations in 4-year-olds, both with and without linguistic cues. Absent linguistic cues, children showed no evidence of encoding force dynamics; however, the presence of language highlighted these relations, improving children's attention to these broader categories in events. The results are the first to explore the problem of hierarchies in relational language and demonstrate a novel role for language in drawing children's attention to the presence of relations between relations. / Psychology

This dissertation evaluates the untested assumption that the individuation of events into units matters for word learning, particularly the learning of terms which map onto relational event units (Gentner & Boroditsky, 2001; Maguire et al., 2006). We predicted that 3-year-old children’s statistical action segmentation abilities would relate to their verb comprehension and to their overall vocabulary knowledge (Research Question 1). We also hypothesized that statistical action segmentation would facilitate children’s learning of novel verbs (Research Question 2). Largely confirming our first prediction, children who were better able to statistically segment novel action sequences into reliable units had more sophisticated overall vocabularies and were quicker to select the correct referents of overall vocabulary items and verb vocabulary items; nevertheless, they did not have larger verb vocabularies. Unexpectedly, statistical action segmentation did not facilitate children’s learning of verbs for statistically consistent action units. However, children showed greater learning of verbs labeling statistical action part-units than verbs labeling statistical action non-units, providing some evidence for our second prediction. In sum, this dissertation takes an important step towards understanding how event segmentation may contribute to vocabulary acquisition. / Psychology