Figure 1.

Effects of noncontingent injections of cocaine (0.01-0.56 mg/kg) on response distribution under a concurrent schedule of saline and food presentation in monkeys with extensive cocaine self-administration histories. Ordinate, percent of total responses emitted on the injection lever, Abscissa, dose of noncontingent cocaine injection. Point above “S” represent response distribution when saline was the alternative to food. Data are expressed as mean ± SEM. *, significant difference from response distribution in the absence of the response-independent cocaine (p<0.05).