||The Visual and the Haptic Müller-Lyer Illusions: Correlation Study
This study examines the Müller-Lyer illusion in the visual and haptic modalities. We investigated whether positive correlations between performances would be observed when the same participants performed exactly the same task in both modalities. The participants were asked to explore first visually only and then haptically only (or in the reverse order) a display made of two arrowheads fixed at the end of rod which pointed to their left. Then, the participants were asked to give verbal instructions to the experimenter who moved the “central and third arrowhead” until they thought that its apex bisected the length of the rod. Results revealed the presence of a significant positive correlation between the classical errors observed in the two modalities. Moreover, the response time for the visual task was also positively correlated to the time for the haptic one. The results are discussed in relation to the hypothesis assuming that common processes underlie the Müller-Lyer illusion in vision and haptics.