In 1997, I argued that with the loss of Piaget's theory as an overarching guide, cognitive development had become disjointed and a new metatheory was needed to unify the field. I suggested developmental biology, particularly evolutionary theory, as a candidate. Here, I examine the increasing emphasis of biology in cognitive development research…

Play has been difficult to define because it is an aspect of many activities rather than of just a specific kind of activity. Classic theorists such as Piaget and Vygotsky emphasized representational play as play in its purist form, but both immediate and ultimate functions of play can be discerned in simple physical activity play. (Author)

Assesses three sets of Piagetian exclusion operations (of varying the independent variables, of holding the independent variable constant, and tautology) and of levels of thought (concrete through formal) in 33 fifth graders, 27 sixth graders, and 31 seventh graders. (HOD)

Describes three studies that examined how young children distinguish between the real, physical world and the mental world; between objects and thoughts; and between doing something and imagining it. (HOD)