Time course of pseudoneglect in scene viewing

When we view the visual world, our eyes move from one location to another about three times each second. When looking at pictures of natural scenes, neurologically intact individuals show a leftward bias in the direction of their first eye movement. The present study investigates the time course of this pseudoneglect and how it depends on task-related control. Eye movements were recorded from 72 participants, each viewing 135 scenes under three different viewing instructions (memorization, esthetic preference judgment, object-in-scene search). In the memorization and preference tasks, pseudoneglect had a maximum extent of about 1° and lasted for about 1500 msec, or 5 fixations. The effect was somewhat reduced in the preference task, which gave subjects free reign to fixate anywhere they wanted to. During scene search, a task that is guided primarily by top-down control, observers also showed a distinct pseudoneglect. Strikingly, a leftward bias was present even when the search object was located in the right hemispace. Search performance was not affected by the observed spatial asymmetries. The effects likely arise from a right-hemisphere dominance for visuo-spatial attention.