. Infants' and young children's representations of objects and non-cohesive entities

This thesis addresses two challenges to the core cognition hypothesis involving infants' representations of cohesion and solidity. The first asks how, given domain general learning mechanisms that operate over sensory stimuli, we can tell whether the knowledge infants display is part of core cognition. That is, how do domain-specific core knowledge systems differ from others? According to the core cognition hypothesis (e.g. Spelke & Carey, 1994), infants represent objects as spatiotemporally continuous, solid, cohesive, and as adhering to the constraint of contact causality on object movement. Yet not all entities in the infants' world (the water they are bathed in, the milk they drink, the earliest food substances the eat) are solid, cohesive objects. Thus Papers 1 and 2 use one specific non-object, the non-cohesive entity, to explore how infants come to represent entities that fall outside the domain of objecthood. Paper 1 demonstrates 8-month-old infants' failures to index, track, and create working memory files for portions of non-cohesive entities, while Paper 2 shows that in the first year of life, infants do not represent non-cohesion as a stable, projectable property. These findings underscore the privileged status of solid, cohesive objects in infants' representations of material entities, suggesting that entities that lie outside this realm must be learned about in a very un -core knowledge-like, piecemeal fashion. Paper 3 asks why, if 2- to 3- month -old infants represent the solidity constraint for objects, 2- to 3- year -old children fail in search tasks thought to rely on this knowledge. Using spatial language as a dependent measure, we provide evidence that one of the problems toddlers face is creating or maintaining a representation of the spatial relation between the hidden object and the barrier (i.e. the shelf onto which a ball was dropped). While the format of this representation need not be linguistic in nature, we demonstrate that linguistic encoding can help the child by making the hidden spatial relationship more salient and/or by providing a means for which the child can maintain an explicit representation of that spatial relationship in working memory in a task that relies heavily on executive functioning.