Orality, preference behavior, and reinforcement value of nonfood object in monkeys with orbital frontal lesions.

Monkeys with orbital frontal ablation, compared with sham-operated controls, showed enhancement of oral tendencies toward nonfood items. Further, unlike the controls, they persistently performed an instrumental response for one of these nonfood items. On the other hand, the lesioned monkeys did not show altered preferences for food versus nonfood items. These findings suggest that reinforcement value and preferential ordering are dissociated by orbital frontal ablation.