Iwahara ( 1959) has maintained that spontaneous alternation behavior is a function of two competitive variables: inhibition and response preference. The inhibitory factor may be either response-oriented (reactive inhibition) or stimulus-oriented (stimulus satiation, stimulus curiosity, stimulus change). Response preference or position preference is added in order to explain the finding that there is less than 50% alternation in animals and human adults (Iwahara, et al., 1959; Iwahara, 1959). A very low percentage of alternation behavior or, more properly, response fixation, was clearly shown when the animal was motivated by electric shock (Iwahara, et ul., 1957; Fowler, et al., 1959; Iwahara, 1960), when the hungry rat was tested in jumping situations (Jackson, 1941), when tested after electro-convulsive shock (Fujita, 1959), and when brain lesions were present (Morgan & Stellar, 1950). These results may be explained in terms of regression to position preference due to strong pain, stress, conflict, and brain injury. Iwahara's (1960) shocked rats showed 45.7% alternation with a 0-sec. intertrial interval, but it decreased to 17.5% and 10.2% when the interval increased to 3 min. and 24 hr., respectively. The finding was explained in terms of an inhibitory factor and position preference rather than by reinforcement on the basis of the fact that elimination of learning was attempted by having the rat reinforced to both sides equally often during preliminary training. On the other hand, Fowler, et al. (1959) interpreted similar results in terms of reinforcement by shock reduction. The purpose of the present study was to investigate whether response fixation in the free-choice situation is a function of reinforcement or regression to a pre-established position habit.