Chlorpromazine exerts stronger suppressive action on the instrumental responses motivated by social than by alimentary reward.

Experiments were performed on six dogs over-trained before treatment, in differentiation of two instrumental responses, i.e. reinforced either by food or by sensory-social reward (petting by the experimenter). Chlorpromazine was injected intramuscularly (1.5 mg/kg) in two separate series. In the first series the drug was given four times during two weeks (twice a week). In the second series, it was injected every day for four consecutive days. Chlorpromazine produced a decrease of performance and an increase of response latencies and errors but this effect was much more evident with social than with alimentary reward. The effect of the drug was similar in both variants of the experiment, although it was more pronounced in the second than in the first series. Food intake was not changed. The motor and autonomic disturbances produced by the drug were not correlated with the decrease in instrumental performance. It is suggested that chlorpromazine acts rather on motivational or rewarding processes than on hunger drive or instrumental performance as such.