It was hypothesized that the orientation reaction mediates sensory preconditioning. The test of the hypothesis consisted of habituating the orientation reaction to the two stimuli used in sensory preconditioning in one group of rats and comparing their performance to a group whose orientation reactions were not habituated. The results clearly indicate that repeated exposure to two stimuli hinders the development of a learned association between them when they are subsequently paired and, thus, support the hypothesis.