Modal completion: critical variables in apparent transparency

Conditions for perceptual modal completion are investigated using a stimulation pattern consisting of a figure moving behind a black opaque strip. This configuration leads, depending on conditions, either to the amodal Michotte tunnel effect, or to modal completion, ie the apparent transparency phenomenon. Four experiments are reported in which an attempt was made to define the critical variables of this latter effect. The results show that modal completion is not typically related to luminance interactions, ie to assimilation, but depends on the figural dominance of the filled-in object, this being determined by structural factors such as figure-ground relationship and stimulation change. The effect also depends strongly on the complexity of the spatiotemporal integration needed to maintain phenomenal identity of the object. No significant effect was found for the two other variables investigated, ie formal complexity of the figure and depth between the figure and the strip. The data are discussed in relation to those on moving visual phantoms.