When the likelihood of receiving reward on either option was probabilistic (0.4:0.1; 0.5:0.2; 0.75:0.25) and thus required the integration of trial-by-trial reinforcement information, the ACCs-lesioned animals were significantly slower to approach the optimal response allocation rate (Figure 9b). However, when the outcome was deterministically rewarded (1:0), they performed comparably to the controls and were thus able to sustain a rewarded response when the contingencies did not switch. As in the previous experiment, impairments were not restricted to situations of non-reward or errors. A comparison could be made of the likelihood of sustaining or switching between responses as a function of both whether the previous action selection had been the more or less profitable option and whether the animals had received a reward for that choice. Following selection of the more profitable action, the monkeys in the ACCs-group were less likely to continue choosing this response whether it was previously rewarded or unrewarded. The converse was true for the less profitable action, with the ACCs-lesioned animals being more likely to sustain this response than controls regardless of the outcome on the
