For balls and goals appearing smaller and narrower, it’s almost like “the perceptual system offers us self-serving justifications for bad performance,” wrote neuroscientist Christof Koch in an essay about Witt’s work in Scientific American Mind. “But there is likely some value here, evolutionarily speaking: If people perceive the goal as higher or smaller than it actually is, they will aim more precisely the next time.”
But the idea that what we see is so easily impacted by action hasn’t gone without dispute. Witt’s faced very vocal responses to her research, which she thinks is because she’s upended the typical chronology of “see, think, act,” by finding that “act” can influence that sequence earlier than was thought possible.
Two of her critics, Brian Scholl and Chaz Firestone from the department of psychology at Yale University, have published on the pitfalls they think her research encounters: that the sample sizes are too small, or that it’s hard to discern between perception and judgment—did participants really see the hill as steeper, or just remember it as such? “I think the idea of action changing how we see is fascinating,” Scholl says, but also that he considers the findings to be generating more excitement than might be warranted. “The science itself doesn’t run nearly as far as it would need to,” he says.
One of Scholl and Firestone’s most pressing concerns is about response bias: they think that in many perception and action studies, the participants can easily guess the purpose of the study, and as a result, their responses can be skewed. For example, if someone was asked to gauge how steep a hill was, and then given a heavy backpack and asked again—they might infer that the hill is supposed to look steeper, and then perceive it as such.
Witt has performed a new study, recently published online in Psychological Science, to directly address the response bias issue. She used a computer game, similar to Pong, which she says has been their most consistent and robust way to elicit the influence of action on perception. People in the study use a joystick to block a ball with a paddle of varying sizes, which makes the task easier or harder. When asked about the speed of the ball, those with smaller paddles perceived the ball as faster—even though the ball’s speed remained the same no matter what paddle size they had.
This time, after the participants played the game, Witt gave them a survey, explicitly asking if they knew the purpose of the study. Only 25 percent guessed correctly, and Witt says that when she compared their results to others who didn’t guess the study’s purpose, they still showed the same effect—that the perception of ball speed was related to paddle size. “It pretty strongly rules out the critics’ claim of this being about response biases,” Witt says.
Witt also included another suggestion from Scholl and Firestone into this study: an element of misdirection. She gave some of the Pong games a blue background and some, a red one. “It was totally irrelevant to our purpose,” she says. “But we hoped it would mislead participants. And we did find that several participants said [the goal of the study] was to see if the ball moved faster when the background is red.” Still, even the participants who incorrectly guessed the study’s purpose showed the Pong effect, Witt says.
Scholl still isn’t sold. “I don’t ultimately find this new study to be convincing, but I am very glad to see this kind of work appearing,” Scholl says, “These are exactly the sorts of careful and critical controls that have been sorely missing from this literature since its inception. And we should indeed be holding this sort of work to a high standard. In part, this is for scientific reasons–since this work flies in the face of everything we know about how perception works. And in part, this is for social reasons—because the proponents of such effects argue that they merit possible changes in policy in real-world contexts ranging from gun violence and vehicular safety to athletic performance and medical diagnosis.”
Scholl continues to finds many elements of this effect unbelievable, and contradictory to other ways that your brain can distort perception. “Optical visual illusions… persist despite your beliefs and intentions (or what language you speak, or how you’re acting, etc.),” he says. ” But this work, in contrast, suggests that what you see can change willy-nilly depend on what you’re doing– or even just what you intend to do.” Scholl says that the survey Witt included is only the first of many steps which would lead to him being convinced.