Selective adaptation vs. transfer of decrement: the conjoint effects of neural fatigue and perceptual learning.

Abstract

Statement of Problem In the last few years, my colleagues and I have been interested in the processes underlying the perceived reversals of reversible figures (Long & Toppino, 1981; Long, Toppino, & Kostenbauder, 1983; Toppino & Long, 1987). One ofthe approaches we have used in our work is the popular selective-adaptation paradigm as a means by which to identify the potential role in this type of illusion of localized neural mechanisms that are subject to fatigue. In this method, an inspection figure is viewed during an adaptation period of perhaps 2-3 min, and a test figure is then shown which shares certain hypothesized features with the adaptation figure. To the extent that the prior adaptation alters the perception of the test figure, one can conclude that similar localized mechanisms are involved in the perception of both figures. This selectiveadaptation paradigm has proven extremely powerful in the investigation of numerous illusions, such as the tilt aftereffect, the motion aftereffect, and the size aftereffect. Reflecting its current popularity, the selective-adaptation paradigm has been referred to as the psychologist's electrode (Frisby, 1980) with which to probe the tuning and response characteristics of hypothesized neural channels in the visual system (e.g., Regan, 1982). In our work, we have attempted to demonstrate the role of localized fatigue effects on the reported reversals of the rotating Necker cube. In this illusion, a threedimensional Necker cube frame is rotated about one of its vertices at a constant speed. An observer viewing either the cube itself or its shadow reports a striking change in the perceived direction of rotation when the cube changes its perspective. As with other reversible figures, the number of reported reversals increases and then levels off at a high rate during a 2-3-min viewing period. For several reasons, we (and others) have proposed that this changing reversal rate reflects fatigue effects in particular visual channels; in our work, we have attempted to demonstrate the limited (i. e., local) character of this fatigue by means of the selective-adaptation paradigm. In one recent experiment (Toppino & Long, 1987, Experiment 1), a rotating cube in the left (or right) visual field was viewed for a 2-min adaptation period, which was followed immediately by a 2-min test period with a cube in the same or