Investigating the contribution of metacontrast to the Fröhlich effect for size

According to the Fröhlich effect, observers perceive the initial position of a fast moving stimulus displaced in the direction of motion. On the basis of Kirschfeld and Kammer’s as well as Fröhlich’s original assumption that metacontrast plays an important role in the emergence of the phenomenon, we predicted different amounts of misperception for stimulus enlargement compared to stimulus reduction. These basic predictions were confirmed in Experiment 1. In Experiment 2, we investigated whether an overestimation-bias might account for these results. But the overestimation of non-changing stimuli was too small to adequately explain the dissociation. In Experiment 3, we predicted and found different effects of the factor stimulus lightness on misperception in the enlargement and reduction condition. In Experiment 4, we showed that misperception in the enlargement condition is reduced when frames are used instead of filled stimuli, as in the earlier experiments. Results are discussed with respect to the original Fröhlich effect.