Reactions to familiar and novel objects in infant monkeys with neonatal temporal lesions.

Adult monkeys with late temporal lobe damage are known to touch and mouth objects compulsively, even unknown objects. To determine whether infants with early temporal damage display this symptom as well, 9-month-old rhesus monkeys with neonatal ablations of either the medial temporal lobe or inferior temporal cortex were exposed to four objects, two familiar and two novel. All operated infants were less active/more withdrawn than controls and showed neither exaggerated object manipulation nor hyperorality. Furthermore, like controls, they touched novel objects less than they touched familiar ones. Thus, infants with neonatal medial or inferior temporal ablations did not display the compulsive exploration evidenced after similar lesions in adulthood and retained some ability to detect novelty despite their known memory impairments.