"Identifying two extreme temperamental types in very young babies - high-reactive and low-reactive - Kagan and his colleagues returned to these children as adolescents. One of the infant temperaments predicted a cautious, inhibited personality in early childhood and a dour, anxious mood in adolescence. The other temperamental bias predicted a bold, uninhibited childhood personality and an exuberant, sanguine mood in adolescence. These personalities were matched by different biological properties." "In a masterly summary of their wide-ranging exploration, Kagan and Snidman conclude that these two temperaments are the result of inherited biologies probably rooted in the differential excitability of particular brain structures. Through the authors appreciate that temperamental tendencies can be modified by experience, this compelling work reveals the long shadow that temperament can cast over psychological development."--BOOK JACKET.