Direction-specific and position-specific effects upon detection of displacements during saccadic eye movements.

We examined the probability that a displacement during a horizontal saccade of either of 2 points of light would be detected, as a function of direction (up, down, or in the same or opposite direction as the saccade) and as a function of whether the point was the start or the target for the saccade. Vertical displacements are all easier to detect than horizontal; for horizontal movements detection is determined by an interaction between direction and position; finally. when the rarger objectively moves, subjects very often incorrectly assign the movement to the start (but not vice versa); this suggests that the rarger for a saccade in these conditions may be assigned as a frame of reference for other perceptual events.