Reviews Greenough, Black, and Wallace's (1987) conceptual framework for understanding the effects of early experience and sensitive periods on development, and illustrates the applicability of their model with recent data on the consequences for animals and human infants of the acquistion of self-produced locomotion. (BN)

The developmental pattern of concurrent synaptogenesis in rhesus monkeys is consistent with a straightforward model of relations between brain and cognitive development. Concurrent synaptogenesis is hypothesized to lay the primary cortical foundation for a series of developmental levels in middle infancy that have been empirically documented in…

Considers areas of consensus from commentaries, including the value of an evolutionary perspective and the utility of exploring variations in physical activity play. Examines areas of debate, including the nonplay-play distinction, functions of rough-and-tumble play, and the opportunities of juveniles for exercise training. Calls for more directed…

Considers the nature and developmental functions of physical activity play. Distinguishes three kinds of physical activity play with consecutive age peaks: rhythmic stereotypies, exercise play, and rough-and-tumble play. Considers gender differences and function in terms of immediate and deferred consequences in physical, cognitive, and social…

Maintains that the "getting into shape" hypothesis of explaining the inverted-U distribution of exercise play across age is likely incorrect. Argues that the biological study of human physical activity play, as recommended by Pellegrini and Smith (1998), will reveal whether physical activity play represents an example of…