Changes in visual spatial organization: response frequency equalization versus adaptation level.

Two experiments tested alternative explanations for the apparent change in visual spatial organization produced by exposure to "adapting" or anchor stimuli. The alternative positions evaluated were that the change was perceptual (adaptation-level [AL] theory) or that it was the result of response bias (response-frequency-equalization theory). In Experiment I, judgments of spatial organization were obtained for 11 different matrices of dots in a series ranging from columnar organization to rowlike organization. The 5s were exposed on alternate trials to dot patterns of extreme horizontal (rowlike) organization, to extreme vertical (columnar) organization, or to neither (control group). As predicted by both theories, judgments were systematically affected by the adapting stimuli. In Experiment II, the influence of response bias was nullified by a forced-choice procedure. Contrary to AL theory, once response bias was eliminated group differences vanished.