Frame of reference transformations in motion perception during smooth pursuit eye movements.

Smooth pursuit eye movements change the retinal image velocity of objects in the visual field. In order to change from a retinocentric frame of reference into a head-centric one, the visual system has to take the eye movements into account. Studies on motion perception during smooth pursuit eye movements have measured either perceived speed or perceived direction during smooth pursuit to investigate this frame of reference transformation, but never both at the same time.

Localization and motion perception during smooth pursuit eye movements.

We investigated the relationship between compensation for the effects of smooth pursuit eye movements in localization and motion perception. Participants had to indicate the perceived motion direction, the starting point and the end point of a vertically moving stimulus dot presented during horizontal smooth pursuit. The presentation duration of the stimulus was varied.

Saccadic search performance: the effect of element spacing.

In a saccadic search task, we investigated whether spacing between elements affects search performance. Since it has been suggested in the literature that element spacing can affect the eye movement strategy in several ways, its effects on search time per element are hard to predict. In the first experiment, we varied the element spacing (3.

Crowding degrades saccadic search performance.

The identity of a target is more difficult to acquire when it is surrounded by distracters. The purpose of the present experiments was to investigate the implications of this crowding phenomenon for performance and eye movements in a real-life task as search with eye movements. The participants searched for a target in a one dimensional search strip.

Perceived motion direction during smooth pursuit eye movements.

Although many studies have been devoted to motion perception during smooth pursuit eye movements, relatively little attention has been paid to the question of whether the compensation for the effects of these eye movements is the same across different stimulus directions. The few studies that have addressed this issue provide conflicting conclusions. We measured the perceived motion direction of a stimulus dot during horizontal ocular pursuit for stimulus directions spanning the entire range of 360 degrees.

Inhibition of return is not a foraging facilitator in saccadic search and free viewing.

The ability to search and scan the environment effectively is a prerequisite for spatial behavior. A longstanding theory proposes that inhibition of previously attended loci (Inhibition of return; IOR) serves to facilitate exploration by increasing the likelihood to inspect new areas instead of returning to locations that have been inspected before. In this eye movement study we tested whether we could find evidence in favor of this hypothesis.

Vertical object motion during horizontal ocular pursuit: compensation for eye movements increases with presentation duration.

Smooth pursuit eye movements change the retinal image motion of objects in the visual field. To enable an observer to perceive the motion of these objects veridically, the visual system has to compensate for the effects of the eye movements. The occurrence of the Filehne-illusion (illusory motion of a stationary object during smooth pursuit) shows that this compensation is not always perfect.