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Object play in primates is view ed as generally having no immediate functional purpose, lim ited
for the m ost part to immature individuals. A t the proximate level, the occurrence o f object play in
immatures is regarded as being intrinsically self-rewarding, with the ultimate function o f supporting motoneuronal developm ent and the acquisition o f skills necessary to prepare them for survival
as adults. Stone handling (SH ), a solitary object play behaviour occurs, and has been studied, in
m ultiple free-ranging and captive troops o f provisioned Japanese macaques, as w ell as rhesus and
long-tailed macaques for over 35 years now. A review o f our com bined findings from these observations reveal that infants acquire SH in the first 3-4 months o f life and exhibit increasingly
more com plex and varied behavioural patterns with age. The longitudinal data show s that many
individuals maintain this activity throughout life, practicing it under relaxed ecological and social
conditions. The ultimate function may be bim odal, promoting motor developm ent in young and
neural maintenance and regeneration in adult and aging individuals
