Extinction of rats’ barpressing in the presence of free food

In two experiments, hungry rats received four extinction sessions in the presence of free food. When the free food was removed for eight subsequent extinction sessions, the animals made significantly fewer responses than did control groups which received no intervening sessions. The results are contrary to those of Enkema et al (1972). From the results of additional groups of rats which received four intervening sessions of free food only, empty chamber, or time in home cage, it was concluded that the presence of free food caused the diminution in extinction responding.