"Over the past forty years, Jerome Kagan has done more than virtually any other developmental psychologist to advance the scientific study of early childhood. In his distinctive style - the personal essay supported by pillars of research on both animal and human subjects - Kagan now challenges his colleagues to recognize that more than one mental foundation underlie the diversity of behavior, emotion, and thought.

Kagan focuses mainly on two qualitatively different modes of mental representation: perceptual schemata and semantic networks. Novelty and the recognition of discrepancy are the engines of change, whether in the perception of surprise or the more prolonged and unpredictable experience of uncertainty."--BOOK JACKET.