The trial context determines adjusted localization of stimuli: reconciling the Fröhlich and onset repulsion effects

It is known that observers make localization errors in the direction of motion when asked to localize the perceived onset position of a moving target (Fröhlich effect). However, recent studies also revealed the contrary: In the onset repulsion effect, the error is opposite to the direction of motion. In four experiments we demonstrate that the conflict between these findings is resolved by considering the trial context: when the stimuli appeared at predictable positions to the left or right of fixation, pointing responses to the perceived onset position were displaced in movement direction. In contrast, when the stimuli appeared at unpredictable positions in the visual field, pointing errors were displaced opposite to motion or at least drastically reduced. Thus, localization of the perceived onset position varies with the trial context.