SOme effects of training conditions on the control exerted by compounded stimuli

Abstract

Rats were exposed to two bars. In Phase 1, presses on the changeover bar alternated among three stimulus elements: a light, white noise and a buzzer. Presses on the response bar were reinforced on a separate variable-interval 160 second schedule during each stimulus element. Additive summation did not occur when the elements were later presented together. In Phase 2, changeover bar presses alternated among the three elements and a condition in which all elements were absent which was correlated with extinction. When the elements were again presented together, additive summation did occur. Summation was often greater to the compound of all three elements than to compounds of two elements. The results show that the presence in training of a condition correlated with a lower reinforcement rate or response rate than the elements compounded and with the absence of the elements is necessary for additive summation to occur.