Self-control: why should sea lions, Zalophus californianus, perform better than primates?

Four sea lions were assessed for their ability to master a reverse-reward contingency task. The subjects were presented with two stimulus arrays of one and five fish and received the array they did not choose. Three subjects spontaneously learned to choose the smaller of two food quantities to obtain the larger one, although their initial choices were for the latter. The fourth subject learned to select the smaller quantity after the introduction of a large-or-none contingency. When confronted with new combinations of quantity, the subjects almost always selected the smaller quantity, showing that they were able to generalize the rule. The results suggest that sea lions appear to perform better than primates tested under the same conditions. Performance in reverse-reward tasks is probably related to food-searching strategies in natural habitats.