Illusions induce contradictory perception of motion.

Can we perceive motion and stillness simultaneously? Philosophical studies suggest that the perception of illusory motion can involve both of these contradictory contents. We examined this possibility by asking participants to rate both perceived motion and perceived stillness using stimuli with illusory or physical motion. The results showed that the negative correlations between the two ratings were much weaker in illusory motion, suggesting that motion and stillness can be disentangled in illusory motion perception. This is the first empirical examination of the hypothesis that perception can involve contradictory contents.