Figural aftereffects as optical illusions? Failure to replicate two results

Abstract

Stadler (1972) has reported two experiments which suggest that (a) the figural aftereffect bound to the retinal image of an inspection circle is weaker than the figural aftereffect bound to the spatial frame of reference, and (b) imagining an inspection circle can produce a figural aftereffect. The results of the seven experiments reported here indicate that these results are not replicable when using objective methods.Stadler (1972) has suggested that the concentric circles configuration shown in temporal sequence in Fig. 1 produces two figural aftereffects (F AEs). A test (T) circle will appear smaller if it is presented within the retinal image of the inspection (I) circle. This retinally bound FAE (FAE r ) is explained by most neurophysiological models, which assume that the neural medium in which F AEs occur is isomorphic with the retina. Stadler also suggests that a T circle wiII appear smaller if it is presented within the location of the 1 figure in the spatial frame of reference. He implies that this spatially bound F AE (F AEs) cannot be explained by neurophysiological models because it is not dependent on the retinal image. EXPERIMENTS I AND IIStadler reported an experiment which was designed to measure the relative strengths of F AE r and F AEs (F AEr-s) and their combined strength (F AEr+ s). The S fIxated to the right of an 1 circle, as shown in Fig. 1. The 1 circle was removed, and the S shifted his gaze to a point at the center of the visual field, thus splitting the retinal image from the spatial location of the I circle. When the two T circles appeared, T 1 was surrounded by the retinal image and T 2 by the spatial location of the I figure. The T circles were then replaced by a point at the same location as the original point. This was followed by two T circles (not shown), shifted so that the left one fell within the spatial and retinal images of the 1 figure (now combined) and the right one appeared to the right of the fixation point. The apparent sizes of the first two T circles showed that F AEs was stronger than F AEr (FAEr-s was negative). The apparent sizes of the last two T circles showed a weak but positive F AEr+s' The following experiments represent an attempt to replicate Stadler's results with more objective procedures. MethodThe Ss for Experiment I were six males and five females from introductory courses in psychology. They received course credit *Preparation of this paper was supported in part by grants to the author from the Sloan Foundation and the Colgate Research Council. 392 for their participation. The Ss for Experiment II were an additional six males and five females from the same population.The stimuli were drawn in black ink on white cards and were presented in a four-field Iconix tachistoscope. The dimensions of the figures are shown in Fig. 1.The design and procedure were similar to those reported by Stadler, with three major exceptions. First, FAEl"-S and FAEr+s were measured in separate experiments. Although Stadler's procedure is efficient, the F AEr+s measuremen...