Abstract
In the Fröhlich effect, the onset of a moving bar's trajectory is perceived to be located further ahead in the direction of motion. One explanation is that the earliest portion of the motion trajectory is not registered in consciousness. It has been suggested that this happens because of metacontrast masking (Kirschfield & Kammer, 1999), or a lack of attention (Musseler & Achersleben, 1998). In this study, I explored the alternative possibility that the Fröhlich effect happens because the trajectory's onset is shifted forward in space. In experiment 1, the first frame of the moving bar was marked by a different color. If the early portion of the trajectory is not registered in consciousness, the marker should not be perceived. Instead, all subjects saw the marker and perceived it as located further ahead in space. In experiment 2, in addition to marking the first frame with a different color, the trajectory's size was increased or decreased continuously. The color marker appeared not only located forward in space but also as larger or smaller in size. These experiments indicate that the Fröhlich effect is not due to a failure to perceive the beginning portion of motion trajectory. Instead, it is due to a shift of the onset of the motion trajectory. However, such a shift is not simply a forward spatial displacement (experiment 2). I propose that the Fröhlich effect is a special case of the illusory misalignment between the continuous and the sudden changes (Cai & Schlag, 2001).