Phantom flashes caused by interactions across visual space

Abstract

Studies regarding the effects of context on the perception of a visual target's temporal properties have generally addressed the cross-modal integration of auditory context, within a functional or ecological (e.g., Bayesian) framework. A deeper understanding of contextual effects in temporal vision may be gained by drawing connections with the rich models of signal processing developed in the field of spatial vision. To bridge this gap, we investigate a purely visual version of the cross-modal "double-flash" illusion (L. Shams, Y. Kamitani, & S. Shimojo, 2000; J. T. Wilson & W. Singer, 1981). Here, a single target flash can be perceived as several flashes if it is presented in the context of multiple visual inducers. This effect is robust across conditions where the target and inducers are of opposite contrast polarity, in different hemifields, are non-collinear, are presented dichoptically, or are high-frequency Gabor patches. The effect diminishes when target-inducer distance is increased or when the target is moved toward the fovea. When the target is foveated, the effect can still be recovered if the inducers are placed at 3° distance. Finally, we find that multiple target flashes are not "merged" into a smaller number of perceived flashes when presented with singular inducers. These results suggest a cortical mechanism based on isotropic propagation of transient signals or possibly based on higher level event detection. Finally, we find that multiple target flashes are not "merged" into a smaller number of perceived flashes when presented with singular inducers. These results suggest a mechanism based on the propagation of transient signals and argue against the relevance of the cue integration model developed for the cross-modal version of the effect.