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

The purpose of this study was to establish whether wing length and the ability to form spatial mental images and vivid images affected optical illusions obtained in the Müller-Lyer figures, both real and imagined. The study involved a group of 137 fine arts college students who were shown two forms of the Müller-Lyer figures with different wing length (15 and 45 mm). In the imagined situation, a plain horizontal line was presented, and participants were expected to imagine the arrowheads aligned in the same way as in the real situation. Discrepancies in the perception of the horizontal lines in the Müller-Lyer illusion ("Point of Subjective Equality") were measured both in the real and imagined situation. Participants were then asked to complete the Vividness of Visual Imagery Questionnaire and the Measure of the Ability to Form Spatial Mental Imagery. It emerged that, in the condition of 45 mm wing length, participants were significantly more susceptible to the illusion than those in the condition of 15 mm wing length. Additionally, in the real situation, participants scoring high in spatial image were significantly more resistant to the illusion than those scoring low.

The Müller-Lyer illusion through mental imagery

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.

High dissociatives, nature versus nurture?

Non-pathological dissociative experiences are common among the general population, and anyone may experience them to some degree. Thus, the aim of this study was to assess the degree of dissociative experiences such as fantasy proneness, imagination, and absorption in fine arts undergraduates prior to beginning their artistic studies, and at the end of their studies at the faculty of fine arts. Moreover, education undergraduates were used as a comparison group. The sample consisted of 440 undergraduates (204 fine arts, and 236 education undergraduates; 224 first-year undergraduates, and 216 fourth-year undergraduates), who were administered three dissociative experiences tests: Dissociative Ability Scale, Dissociative Experiences Scale, and Questionnaire of Experiences of Dissociation. The working hypotheses were substantiated with dissociative experiences being a distinctive personality trait of fine arts undergraduates. We have found a grade level difference between first-year and fourth-year fine arts undergraduates, although the study does not examine the nature of the change itself. The results are discussed in the light of previous studies, and new lines of research proposed.

Factor structure and reliability of the Spanish version of the Dissociative Ability Scale

Everybody has dissociative ability to some extent, though this may vary from one individual to another. Several tests have been designed to measure dissociative ability, such as the Dissociative Ability Scale (Fisher, Johnson, & Elkins, 2013). Thus, the aim of this study was to assess the reliability and validity of the Spanish version of this test in a sample of 204 undergraduates seeking a fine arts degree at the University of Vigo (Spain). The reliability and validity of the Dissociative Ability Scale was found to be satisfactory for measuring dissociative ability. The results are discussed and innovative lines of research are proposed.