ABSTRACT
In an early study of incentive contrast, Elliott (1928) trained experimental rats to run a maze for bran mash, a highly preferred reward. When these animals were switched to sunflower seed reward they made more errors and ran more slowly than control rats who had been trained from the start with sunflower seeds. This study of incentive contrast has a number of interesting features. First, there was a qualitative change in the reward, from one that was highly preferred to one that was less preferred. Second, a comparison of contrast (i.e., experimental postshift) data was made with data from a control condition to determine if incentive contrast had occurred. In this case, the contrast data were compared to data gathered from a control group of animals who had been run on the same days as the shifted group. Finally, the two incentive conditions were given to the experimental group animals in separate phases of the experiment, so that any contrast exhibited must have been based on a comparison by the experimental animals of the second-phase incentive condition with the previously experienced first-phase condition.
