Landmarks facilitate visual space constancy across saccades and during fixation

It has been demonstrated that visual objects that are present after saccadic eye movements act as landmarks for the localization of stimuli across saccades, facilitating space constancy (Deubel, 2004). We here study the temporal conditions under which landmark effects occur after saccadic eye movements, and during fixation. Two small objects were presented 6 degrees in the periphery, one above the other. Observers saccaded to the space between them. One of the objects disappeared during the saccade and reappeared with a variable delay during or after the saccade. At the same time either that object or the continuously present one jumped by 1 degrees . The observer's task was to decide which object had moved. The results revealed a strong bias to assign movement to the object that was blanked, regardless of which actually moved. If both objects were blanked, the one that was blanked for a shorter time tended to be seen as stable. The effects were stronger as the onset asynchrony between the stimuli increased. Surprisingly, analogous though weaker effects occurred during visual fixation, suggesting that similar visual mechanisms relying on visual landmarks operate both across saccades and during fixation.