Current perspectives on the biological study of play: signs of progress.

There has been a recent resurgence of interest in the study of play behavior, marked by much empirical research and theoretical review. These efforts suggest that play may be of greater biological significance than most scientists realize. Here we present a brief synopsis of current play research covering issues of adaptive function, phylogeny, causal mechanisms, and development. Our goal is to selectively highlight contemporary areas of research in which the underlying processes and consequences of play should not be ignored. We elucidate some of the new and burgeoning areas of play research and interpret them from an integrative biological theoretical perspective that highlights areas in need of further experimental, comparative, and field research.