Geometrical illusions can affect time-to-contact estimation and mimed prehension

Results indicate that under some conditions the Sander parallelogram illusi on can affect time-to-contact (TTC) estimation in a prediction-motion (PM) task and in an interceptive action (IA). The illusion also affected mimed m anual prehension. The implication is that the timing of responses in the PM and IA tasks may involve an estimate of TTC that is based on the perceived dimensions of the environment. Further research is warranted in the develo pment of models of perceived collision and of visually guided actions.