Visual Illusions as a Tool for Dissociating Seeing From Thinking: A Reply to Braddick (2018)

Researchers in our field—like pretty much everyone else—seem to have a collective fascination with visual illusions. A recentPerception editorial, however, wonders whether this is a good idea (Braddick, 2018). In particular, while acknowledging plenty of useful research on (and inspired by) various individual illusions, Braddick asks whether it is really helpful to identify illusions more broadly as a category: “what have we gained by putting them in the same box . . .?” (p. 1). Braddick’s suggestion is that doing so is a mistake motivated primarily by a superficial “innocent pleasure,” but that illusions as a category are actually “deeply unhelpful for science” (p. 1). In an explicit attempt to be provocative, Braddick even suggests that focusing on illusions as a natural kind (i.e. as a privileged grouping that reflects something important about the structure of the mind) is an “infantile disorder.” In this respect, Braddick’s editorial succeeds admirably: we are provoked! In particular, we are provoked to explain why we disagree: we think that “illusions” are a natural kind whose existence has profound implications for our (scientific!) understanding of seeing, thinking, and especially how seeing and thinking do and do not interact. This is a theme that has figured quite a lot in recent debates about how cognition may influence perception, but curiously it was not mentioned either in Braddick’s editorial or in subsequent defenses of the importance of illusions (e.g., Shapiro, 2018; Todorovic, 2018).