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The nature of infants' early shape bias : the role of kind concepts, object domain, and learning Dewar, Kathryn Megan


The studies in this thesis address two central issues that remain unresolved in the developmental literature. The first issue concerns the question of whether infants’ earliest object labels refer to distinct shapes or distinct kinds (Study One and Two). The second issue concerns the question of the origin of infants’ early linguistic sensitivity to shape, that is, identifying the potential mechanism through which a ‘shape bias’ may be learned (Study Three). All three studies employ the violation of expectancy looking-time method. Study One examined whether infants expect labels for objects in different domains to have different perceptual correlates or whether they have a general expectation that object labels refer to distinct shapes. Infants were presented with food objects: an object domain in which shape is not the primary perceptual correlate of kind. The findings indicate that when the labeled objects are food, both 9- and 12-month-olds demonstrate some color sensitivity and, moreover, infants do not expect food objects differing in shape to be marked by distinct labels. These findings provide evidence that, for infants, distinct labels do not solely correspond to distinct shapes. Study Two examined infants’ expectations about internal properties of labeled objects (as opposed to external object properties, such as, shape). Findings indicate that 10-month-olds are able to use linguistic information (the number of distinct object labels applied to an object pair) in order to predict whether a particular pair of objects should make the same sound or different sounds, regardless of the object pairs’ perceptual similarity or dissimilarity. These findings suggest that infants hold kind-relevant expectations about labeled objects. Study Three examined whether 9-month-olds (the youngest age group to demonstrate a shape sensitivity in their linguistic expectations) were capable of forming overhypotheses across feature variability. An overhypothesis is a second-order induction: it allows a learner to make predictions about an entire category based on evidence from only a few category members. Findings indicate that 9-month-olds are able to form overhypotheses flexibly, over multiple property dimensions. These results suggest that infants have at their disposal a powerful learning mechanism capable of supporting the formation of strong inductive inferences.

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