Rats place greater value on rewards produced by high effort: An animal analogue of the “effort justification” effect

The effort justification phenomenon, in which greater value is given to rewards that require more effort to obtain, is frequently explained in terms of cognitive dissonance (Festinger & Carlsmith, 1959). Here, we employed a novel combination of operant and lick analysis techniques to show that rats place more value on a sucrose reward when it follows high effort than when the same reward follows low effort. This is the first demonstration of a direct analogue of the effort justification phenomenon in nonhuman animals. As the behavior of rats is normally considered in terms of relatively simple mechanisms, the current results question the need for complex cognitive accounts for the effort justification phenomenon (in rats or humans). As an alternative, we examine the possibility that high effort produces an aversive state that enhances reward value by a process of contrast.