Müller-Lyer Illusions: Their Origin in Processes Facilitating Object Recognition

Abstract

Perspective theories for the Muller-Lyer illusions have considered them to reflect constancies normally permitting the viewer to compensate for distance in estimating the true size of three-dimensional objects. Our experiments suggest a rather different perspective theory involving object recognition.A novel experimental procedure was used. Each of the separate groups of thirty subjects viewed only one of nineteen experimental drawings based on the Muller-Lyer figures. They judged the overall length of the shaft and divided it into subjectively equal quarters. The major findings were that the effect of each component angle was generally independent of other angles and independent of any overall perspective appearance of the figure. The shortening effect produced by an acute angle was limited to the contiguous quarter, while the lengthening effect of an obtuse angle extended undiminished from the contiguous quarter to the next quarter.Perspective photographs are shown, demonstrating that these angle-induced changes in apparent length can compensate selectively for the different perspective distortions occurring for the component parts of a single three-dimensional object. Such expansions and contractions provide no direct help in estimating overall size or distance of the object. But they do make possible recognition of the actual shape of the object and its orientation to the viewer, as well as producing errors when judging the length of Muller-Lyer figures.

The role of structural components in the Mueller-Lyer illusion

“…A systematic reduction in apparent expansion was found with the successiveremoval of the wings in the wingsout figure: The decreases in the apparent extent of the shaft-present wings-out figure were 3.04, 4.54, and 6.34 mm when two wings, three wings, and four wings, respectively, were amputated. In contrast, for the wings-in figure, previous investigators have found no decrease in underestimation with removal of two wings (Warren & Bashford, 1977) or a decrease that is dependent upon the placement of the remaining wings (Day & Dickinson, 1976a). Furthermore, a decrease in illusory magnitude has been reported for the removal of three wings, yet the degraded figure was still significantly underestimated (Day & Dickinson, 1976a;Warren & Bashford, 1977).…”

“…Support for a dual-illusion hypothesis is suggested by the differential changes in illusory magnitude that were observed for the Mueller-Lyer wings-in and wings-out figures with systematic wing amputation in the first study and in previous studies (e.g., Day & Dickinson, 1976a;Warren & Bashford, 1977). A systematic reduction in apparent expansion was found with the successiveremoval of the wings in the wingsout figure: The decreases in the apparent extent of the shaft-present wings-out figure were 3.04, 4.54, and 6.34 mm when two wings, three wings, and four wings, respectively, were amputated.…”

“…variations (Figure 1) were reproduced on sheets of 21.6 x 27.9 em white paper. Yariations that eliminated the wings of the standard figures (Figures lC through IF) were selected based on the availability in the literature of data on analogous versions (Warren & Bashford, 1977).…”

“…; see Robinson, 1972, for a review of configural manipulations and a historical review of the Mueller-Lyer illusion), there has been little systematic study to determine the critical stimuli within the basic figure for effecting and affecting the magnitude of the illusion. The effect on the magnitude of the illusion has been examined with the removal of the oblique angles or wings (Day & Dickinson, 1976a;Tausch, 1962;Warren & Bashford, 1977) and with the omission of the central line segment or shaft (Cooper & Runyon, 1970). However, of interest is a systematic investigation of the effect of combined figural component amputations on illusory magnitude.…”

Illusion decrement and transfer of illusion decrement in obtuse- and acute-angle variants of the Poggendorff illusion

“…According to Greist-Bousquet and Schiffman (1985), although wings-out overestimation is greater than the wings-in underestimation for conventional full-line Miiller-Lyer figures, the reverse applies for the amputated Muller-Lyer figures. Specifically, as indicated by the results of Greist-Bousquet and Schiffman (1981c) and Warren and Bashford (1977), amputated wings-in MullerThanks are extended to Peter Wende roth for his comments on a draft of this paper, and to two anonymous reviewers for their helpful critical reviews of themanuscript. Correspondence should be addressed to lohn Predebon, Department of Psychology, University of Sydney, Sydney, NSW 2006, Australia. …”