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.

A Factor Analytic Study of Two Measures of Mental Imagery

To examine the factor structure of the Vividness of Movement Imagery Questionnaire and the Visual Elaboration Scale measure, in Study I the former test was given to 133 psychology students and in Study II the latter test to 147 students. Principal components factor analysis yielded one factor for the former and five factors on the latter. The Visual Elaboration Scale has such a complex factor structure that difficulties may arise in interpretation. However, the Vividness of Movement Imagery Questionnaire has a simple unitary structure.

Factor Structure and Internal Consistency of the Spanish Version of the Gordon Test of Visual Imagery Control

We examined the factor structure and internal consistency of the Spanish version of the Gordon Test of Visual Imagery Control, as well as the correlations with scores on the Vividness of Visual Imagery Questionnaire and the Verbalizer-Visualizer Questionnaire, for a sample of 479 undergraduates. Principal components analysis, followed by varimax orthogonal rotation, identified the expected four factors (Movement, Misfortune, Colour, and Stationarity), which jointly explained 55% of the variance. The Gordon Test had a Cronbach α value of .69 and correlated significantly with scores on Marks' Vividness of Visual Imagery Questionnaire.

Measuring Visual Imagery Ability: A Review

The internal nature of visual imagery makes the measurement of visual imagery ability a difficult task. In this review, we describe and evaluate the available measures of visual imagery ability. Several questionnaires of vividness, control, and preference have received favorable psychometric evaluations but these were not created on the basis of a theoretical analysis of imagery ability. Recent development of questionnaires has taken account of theoretical advances. Future research should continue in this vein. Objective tests of spatial ability may not be as appropriate as theory-driven visual imagery tests, as measures of visual imagery ability. The latter should be standardized. The well-known finding of a lack of relationship between subjective and objective imagery measures has been challenged by recent findings. Before this relationship can be fully examined, current measurement should be improved.

Consistency of interform content for the Gordon Test of Visual Imagery Control

A total of 116 undergraduates (49 men, 67 women) completed the Gordon Test of Visual Imagery Control followed immediately by another form. Scores were higher for women than for men and on the original than on the new version. Alternate-form reliability coefficients were .517 for the complete sample, .712 for men, and .210 for women. It was concluded that consistency across content was lower than desirable.