Distribution and changes in strength of hand preference of cynomolgus monkeys.

Monkeys were observed for hand preference during simple reaching for food. The position of the animal relative to the food had only a slight influence upon the strength of hand preference. With repeated reaching, the strength of preference for the preferred hand tended to increase. The hand preferred on the first reach was predictive of that preferred over the entire series of 600 reaches in a significant proportion of individuals. This was not true of the animals presumed to be youngest and suggests that past experimental or developmental factors influence the hand preference displayed in later circumstances.