The influence of directionality bias on vision for action and vision for perception

Thumbnail Image
Ekladuce, Youssef G.
Journal Title
Journal ISSN
Volume Title
I investigated the sensitivity of the visual system to directionality bias by manipulating the likely direction of a horizontally moving target. I went on to examine the generalizability of directionality bias on the visual system during perceptual tasks, for which an action was not required. Forty-eight participants completed a visuomotor task and two line bisections tests, one prior to the visuomotor task and one after it. The visuomotor task consisted of a two-dimensional rectangular target appearing in the middle of a monitor and horizontally translating toward the right or the left. Participants were randomly assigned to one of two groups, a rightward bias group (75% R – 25% L) or a leftward bias group (25% R – 75% L). Results revealed that participants did not make anticipatory fixations in the direction in which the target would move prior to its movement. However, I did observe that following the movement of the target, participants became better at following the target closer to its center, as they completed more trials. Nevertheless, for both, fixations before and after target movement onset, there was no significant difference between the rightward and leftward bias groups. Finally, contrary to my hypothesis, the line bisection task revealed a rightward bias, which was not affected by the directional bias introduced during the visuomotor task. These results suggest that a 75% – 25% bias ratio is not sufficient to cause the visuomotor system to produce anticipatory fixation behaviour. Moreover, the results of the line bisection task did not show pseudoneglect, but instead a rightward bias, providing support for the interhemispheric competition theory of visual attention.
Perception and Action, Directionality Bias, Visual Attention, Anticipatory Fixations, Dual-Stream Theory, Visual Asymmetry, Visuomotor Task, Line Bisection Task