Autocontingencies: Factors underlying control of operant baselines by compound tone/shock/no-shock contingencies

Previous research has shown that postshock acceleration of baseline responding, which normally results from exposure to a shock/no-shock autocontingency, is eliminated when a suppressive tone-shock contingency is simultaneously presented (Davis, Memmott, & Hurwitz, 1975). Three experiments were performed to explore this inability to produce joint suppressive/ accelerative control by compound tone-shock and shock/no-shock contingencies. Progressively degrading the tone-shock contingency in Experiment 1 maintained conditioned suppression and resulted in asymptotic levels of postshock acceleration in all degraded groups. Evidence for accelerative control by the autocontingency was also recorded in a control group that received a totally reliable tone-shock relation. Experiments 2 and 3 pursued this latter finding, which is in direct conflict with our earlier results. The appearance of joint suppressive/ accelerative control by tone-shock and shock/no-shock contingencies appears to be related to the number of shock trials given per session; moreover, relatively small differences in trial density (e.g., three trials per 22.5 min vs. three trials per 30 min) are critical to establishing joint autocontingency control. The importance of shock rate is discussed with regard to the relative waiting time hypothesis, an alternative model of Pavlovian control, as well as to previously reported conditioning failures involving compound suppressive/accelerative procedures.