Can squirrel monkeys (Saimiri sciureus) learn self-control? A study using food array selection tests and reverse-reward contingency

Eight squirrel monkeys (Saimiri sciureus) were presented with 2 stimulus ar rays, namely I and 4 pieces of food, but they received only the array other than the one they reached for. In this reverse-reward condition, all monke ys initially showed a strong preference for the larger array. One monkey le arned to reach toward the smaller array when a large-or-none reward conting ency was applied (i.e., no reward followed a reach toward the larger array, but this array was given for a reach toward the smaller array). When corre ction trials and time-out were added to the large-or-none procedure, all re maining monkeys except 1 learned this form of self-control. Performance was maintained when correction trials were discontinued, the original reverse- reward condition was rerun, and novel array-size pairs were presented. This study demonstrates one form of self-control in a New World primate and sho ws the reverse-reward procedure to be a potentially valuable method for ass essing species and individual differences in self-control and numerosity-re lated abilities.