Abstract

Explored illusion magnitude relationships between the Brentano Mueller-Lyer\nfigure and its 2 component parts, the wings-in and the wings-out\ndistortions. Exp 1 with 24 university students used a within-observer\ndesign, and Exp 2 with 70 university students used a between-observer\ndesign. Results indicate that the traditional measurement of illusion\nmagnitude in the Brentano figure was best predicted by measurements\nof its underestimation rather than its overestimation component.\nBoth experiments confirmed the close association between the Brentano\nfigure and the wings-in component. Wings-out scores were not good\npredictors of Brentano illusion magnitude. Decrement training on\nthe figure generalized to the wings-in but not the wings-out figure.