From a viewpoint of examining the displacement model of Miller N. E., a comparative study was done on the stimulus generalization gradients in approach responses and in avoidance responses. The molel holds the following assumptions. 1) Stimulus generalization gradients should exist in both approach responses and avoidance responses. 2) Avoidance gradient should be steeper than approach gradient. 3) Both gradients should intersect in the existing situation. 4) Displacement should occure the point at which net strength of approach is the largest. The eight experiments were examined to study these four ponints, especially the second and third ones. On 2): Incompatible results were obtained. Some confermed to the model-produced results (Miller  Kraeling; Murray  Miller; Takahashi; Hoffman  Fleshler (Exp. II)), while others indicated contrariwise that approach gradient was steeper than avoidance gradient (Phase 1 by Fearst; Test sessions 5, 10 by Foffman  Fleshier (Exp. 1)). And still in other cases the two gradients were of an identical degree (In the cases of advanced phases by Hearst.) On 3): The experimental results given by Miller  Kraeling, Murray  Miller, Hoffman, Fleshier (Exp. II) demonstrated the intersection between the two gradients, while the result given by Hearst never showed this intersection. Cause of the inconsistency among the experimental results was studied from nine angles. And lastly, the model itself was theoretically observed.