Stephen Downes

My own view of mental imagery is that it is perceptualist, that is, "seeing and mental imagery are fundamentally the same kind of mental state, differing only in degree or in terms of cause." This paper looks at experiments conducted in 1910 by C. W. Perky that many have taken to show that perceptualism is true; there's no difference between our perception of a thing and an image of a thing. As Nigel Thomas writes, "although perception is usually more vivid... than mental imagery, the experiment appears to show that this is, at best, a mere difference in degree." In this paper, Dan Cavedon-Taylor argues against this interpretation of Perky's results. "Given the deceptive nature of Perky's experiments, we cannot be confident that introspection and genuine indistinguishability was responsible for subjects' reports, rather than task demands." Maybe, but I think there are many other phenomena that lead to the same conclusion - the phantom limb syndrome, for example - where no effort has been made at all to fool the perceiver.