Philosophy, Psychology and Neuroscience

The Waterfall Illusion

The Waterfall Illusion occurs when, after watching a waterfall or some other continuously moving body for an extended period of time, we look at a stationary object. Observers usually report that the stationary object appears simultaneously to move and not to move. Many philosophers take these reports at face value and analyse the experience accordingly, as the visual experience of a logical impossibility, thus revealing some tolerance with respect to contradictions. According to them, visual experiences can, indeed, have contradictory contents. If you are a contradiction phobic, however, the idea that we can have visual experiences of logical impossibilities could trouble you deeply, and you may be pleased by some fairly recent non-systematic attempts to analyse the Waterfall Illusion in ways that do not involve the experience of a logical impossibility. Unfortunately, these attempts are defective. In my talk, along with a bit of speculative thought, I present a new account of the Waterfall Illusion that I hope will help soothe your anxieties.