The effect of frustrative nonreward on the attractiveness of the omitted reward

Two experiments were performed to test the hypothesis that omission of a previously received reward is followed by greater motivation to obtain that specific reward, as compared with the case where the reward had been present. In Experiment 1, experimental rats regularly received food rewards (R_a) at one goal, followed by a choice between food and milk (R_b). Control animals received the same choice without food preceding it. Reward magnitudes were manipulated so as to produce a preference for R_b, and additional forced trials were given each day to equalise experience of the two rewards. In the test phase both groups received trials with R_a present (R) or absent (N) at the first goal. The experimental Ss shifted their choice towards R_a on N trials; the controls did not behave differently after R and N. Experiment 2 was similar, except that R_a was milk and R_b food. The same effect of N on experimental animals was obtained. It is argued that the results are relevant to the double-runway ‘frustration effect’, and cannot be explained by existing theories of frustration.