The Müller-Lyer illusion through mental imagery

Abstract

Previous studies have pointed to a link between visual perception and mental imagery. The present experiment focuses on one of the best-known illusions, the Müller-Lyer illusion, now reproduced under conditions of real perception and by means of imagery. To that purpose, a tailored ad-hoc set of combined figures was presented to a total of 161 fine art students (M age = 20,34, SD = 1,75) who individually worked with two different variations of the Müller-Lyer figures which consisted of a 10 mm long shaft and two fins set at an angle of 30º, being 15 mm long in one instance and 45 mm long in the other. In small groups, participants also completed an image control questionnaire. Results yielded that the longer the oblique lines, the larger the magnitude of the illusion both in the situation of real perception and in the imaginary situation. Also, the magnitude of the illusion augmented in the situation of perception in contrast to the imaginary situation, both with 15 mm long fins and with those of 45 mm. However, no significant differences were found in the magnitude of the illusion between high and low individuals in image control, although interactions between image control and other variables were indeed significant. The consistency of the outcome is a step forward in the study of illusions through mental images and opens the door to new lines of research that could involve innovative methods of analysis, different versions of the illusion and wider groups of participants.

Effectiveness of the ability to form mental images in Müller-Lyer optical illusions

“…Image vividness did not exert any influence on the magnitude of the illusion. The image control ability rendered similar results according to Pérez-Fabello and Campos (2022a). In any case, new studies are needed not only to confirm conclusions but also to learn about new abilities and conditions that counteract geometric illusions, especially the Müller-Lyer illusion.…”

“…Despite the fact that image control ability, as measured by the Gordon Test of Visual Imagery (Richardson, 1969) did not influence the magnitude of the illusion, we were interested in further investigating other imaging skills. We also aimed to reconfirm the influence of wings length as had been attested in previous studies (Pérez-Fabello & Campos, 2022a). For that reason, this essay is meant to find out whether the length of the oblique lines as well as the ability to form spatial mental images and vivid images have any influence on the Müller-Lyer optical illusion, be it in real or imagined situations.…”

“…The figures used in this study were the same as those used by Pérez-Fabello and Campos (2022a), namely the combined or Brentano form of the Müller-Lyer illusion. On this occasion, three figures were tailored.…”

“…However, no significant differences in the magnitude of the illusion were found between individuals high and low in image control ability, although interactions between image control and other variables were significant. With the exception of the study by Pérez-Fabello and Campos (2022a), the few existing reports on the influence of mental images on the Müller-Lyer illusions are all focused primarily on the object, that is, on the Müller-Lyer figures themselves, overlooking people's capacities to imagine figures. Despite the fact that image control ability, as measured by the Gordon Test of Visual Imagery (Richardson, 1969) did not influence the magnitude of the illusion, we were interested in further investigating other imaging skills.…”

“…Pérez-Fabello and Campos (2022a) have recently examined the influence of the Müller-Lyer illusion on participants when asked to imagine the oblique lines of the figures. The authors also analyzed the influence of the ability of image control on participants’ performance.…”