Attentional Shifts and the Mislocalisations at the Beginning of a Movement

When subjects are asked to determine where a fast moving stimulus enters a window, they typically do not localise the stimulus at the edge, but at some later position within that window (Fröhlich effect). We report four experiments aimed at exploring this illusion. An attentional account is tested, on the assumption that the entrance of the stimulus in the window initiates a focus shift towards it. While this shift is under way, the stimulus moves into the window. Because the first phenomenal representation of the stimulus will not be available before the end of the focus shift, the stimulus is perceived at some later position.

In experiment 1 we established the Fröhlich effect and showed that its size depends on stimulus parameters such as movement speed and movement direction. In experiment 2 we tested whether the effect changes when the stimuli started from different eccentricities. In experiment 3 we showed that the processing of the moving stimulus benefits from a preceding peripheral cue, and in experiment 4 we showed with a detection task that feature information about the moving stimulus gets lost when it falls into the critical interval of the attention shift. In conclusion the presented attentional account shows that selection mechanisms cannot only be space-based but that they can establish a spatial representation that is also used for perceptual judgement, that is selection mechanisms can be space-establishing as well.