Voluntary action alters the perception of visual illusions.

"Intentional binding" refers to the finding that people judge voluntary actions and their effects as having occurred closer together in time than two passively observed events. If this effect reflects subjectively compressed time, then time-dependent visual illusions should be altered by voluntary initiation. To test this hypothesis, we showed participants displays that result in particular motion illusions when presented at short interstimulus intervals (ISIs). In Experiment 1 we used apparent motion, which is perceived only at very short ISIs; Experiments 2a and 2b used the Ternus display, which results in different motion illusions depending on the ISI. In support of the time compression hypothesis, when they voluntarily initiated the displays, people persisted in seeing the motion illusions associated with short ISIs at longer ISIs than had been the case during passive viewing. A control experiment indicated that this effect was not due to predictability or increased attention. Instead, voluntary action altered motion illusions, despite their purported cognitive impenetrability.