Figure 4.

Mean difference scores of monkeys with bilateral PFo lesions (shaded bars) and unoperated controls (open bars) on two tests of re inforcer devaluation: a test administered with objects overlying food rewards (test 3) and a test with food rewards presented alone (test 4). Monkeys with bilateral PFo removals were only impaired when required to choose objects. The symbols represent scores for individual monkeys: filled diamond, PFo-1; filled square, PFo-2; filled circle, PFo-3; filled triangle, PFo-4; open circle, Con-1; open right-angled triangle, Con-2; open square, Con-3; open equilateral triangle, Con-4; open plus sign, Con-5; open diamond, Con-6.