Prior work showed that infants look longer at impossible figures than possible ones, although it is unclear whether they or older children understand "impossibility." We employed a series of matching and sorting tasks with pictures and objects to evaluate children's knowledge of this dimension. In Experiment 1, nearly all children…

In simple rule-switching tests, 3- and 4-year-olds can follow each of two sorting rules but sometimes make perseverative errors when switching. Older children make few errors but respond slowly when switching. These age-related changes might reflect the maturation of executive functions (e.g., inhibition). However, they might also reflect…

On belief-desire reasoning tasks, children first pass tasks involving true belief before those involving false belief, and tasks involving positive desire before those involving negative desire. The current study examined belief-desire reasoning in participants old enough to pass all such tasks. Eighty-three 6- to 11-year-olds and 20 adult…

Skilled behavior requires a balance between previously successful behaviors and new behaviors appropriate to the present context. We describe a dynamic field model for understanding this balance in infant perseverative reaching. The model predictions are tested with regard to the interaction of two aspects of the typical perseverative reaching…

Eight- to 12-month-olds might make A-not-B errors, knowing the object is in B but searching at A because of ancillary (attention, inhibitory, or motor memory) deficits, or they might genuinely believe the object is in A (conceptual deficit). This study examined how diligently infants searched for a hidden object they never found. An object was…

This study investigated the development of the many-to-one counting strategy in 4- year-old children. In the first experiment, 52 children participated. Their development with respect to two kinds of tasks, a hidden-items task and a needed-items task, was studied over four sessions. Children (n = 28) who accurately used the many-to-one strategy in…