Effects of six experimental manipulations on the learning of a new escape response

Abstract

The deleterious effect of previous exposure to uncontrollable aversive events on subsequent learning is called learned helplessness. This study investigated the effect of six experimental manipulations on the acquisition of an escape response. Forty eight rats were divided in six groups of eight. Three experimental sessions were conducted with each rat. In the first session three different conditions were administered, depending on the group: in the first condition, animals received shocks that they could interrupt; in the second condition, animals were yoked to those in the first condition and could not interrupt shocks, which were interrupted by responses of the yoked animal; in the third condition, animals did not receive shocks. In the second session, half of the animals in each condition received uncontrollable shocks and the other half did not receive shocks. The third session tested whether animals could learn a response to escape shocks. Rats that could interrupt shocks in the first session, even if they received uncontrollable shocks in the second, learned to escape shocks in the test. Those that initially received uncontrollable shocks did not learn to escape in the test. These results replicate earlier findings on learned helplessness. However, the poor performance in the test by the group that did not received shocks leads to questions about the contingency used to evaluate learning.

Keywords: learned helplessness; escape responses; rats.