ILLUSION DECREMENT IN WINGS-IN AND WINGS-OUT MULLER-LYER FIGURES

Illusion decrement with inspection was assessed separately for wings-in and wings-out Müller-Lyer figures. Subjects reproduced the central extent in Müller-Lyer figures under three conditions: the subjects in Experiment 1 made responses at 1-min intervals during a 5-min inspection period, the subjects in Experiment 2 made responses at 1-min intervals without inspection between judgments, and Experiment 3 provided the subjects with implicit feedback during inspection. Separate inspection of wings-in and wings-out figures produced similar decrement effects. Illusion decrement was observed in Experiment 1, but the decrement was comparable to the control condition of repeated judgments without intervening inspection (Experiment 2). When provided with implicit feedback during inspection (Experiment 3), pronounced illusion decrement was obtained, but not for all subjects. The variability associated with responses in all experiments was high, and a large percentage of subjects did not show illusion decrement after 5 min of inspection. Thus, general and firm conclusions concerning reliable illusion decrement are unwarranted. © 1991, The Psychonomic Society, Inc.. All rights reserved.