| Abstract: | After a scalloped lever-press response pattern had developed under a fixed-interval food reinforcement schedule, a 15-sec electric shock was intruded for different groups of rats in the first, second, third, or fourth quarter of each inter-reinforcement interval. Shock intensity was systematically increased for individual rats over 70 sessions, from 0.05 to 1.6 mA. Additional between-groups comparisons involved response-dependent versus clock-dependent fixed-interval schedules, and response-dependent versus response-independent electric shock intrusion. Response rates within each fixed interval prior to, during, and following electric shock intrusion showed regular and reproducible increases and decreases under systematic application of the experimental variables. These results provide further evidence that the functions of a stimulus are determined in part by the parameters of intensity, response contingency, and temporal location with respect to reinforcement. |
