Obese people see distances as farther than they actually are, according to a forthcoming study that suggests overweight people suffer a “vicious circle” of perception and behavior, and that questions the premise that humans see the world as it is.

“If you find yourself out hiking with a heavy backpack, hills are going to look steeper, distances are going to look farther, gaps across a river are going to look longer,” psychologist Jessica Witt told reporters at the annual meeting of the American Association for the Advancement of Sciences (AAAS).

Sixty-six people were recruited from Walmart for the study, which asked the participants to not only estimate distances and inclines but also to play virtual tennis, putt a golf ball, and practice baseball. Body shape influenced perception, Witt said: a 330lb person saw a 25m distance as 30m, and a 130lb person saw that same distance as 15m.

In general, Witt said that obese people see distances at least 10% further than those with an average weight, and people of all heights and weights “grossly overestimate” how steep hills are.

“You’re not seeing the world as it is,” Witt said, “you’re seeing the world in terms of your ability to act.”

Performance at tasks also changed when researchers used illusions to manipulate perception. Volunteers asked to putt a golfball performed worse when the Ebbinghaus illusion made the hole look smaller, for instance, and performed better when it made the hole look larger. Similarly, they perceived a virtual tennis ball as moving slower when given a larger racket, and faster when given a smaller one.

“We think that perception is keeping you from having to think,” Witt said, by slightly distorting how people see the world. She offered the example of seeing a cliff as larger than it is: “That bias is keeping you farther back from the cliff so you don’t get too close and fall over.”

But the inference that the mind unconsciously discourages exerting effort also means overweight people would be more vulnerable to a self-perpetuating system.

“We think that these perceptual biases can create a vicious circle for people with obesity,” Witt said. “It is conscious perception of the world. But it’s not based on conscious perception of the body or feelings of laziness.”

The study, which was performed at Colorado State University in Fort Collins and has been accepted for publication, did not explicitly test the question of what mechanisms affect behavior, though other studies have documented similar behaviors in humans and other animals. Elephants for instance, have been recorded travelling enormous distances to avoid hills, and the steepness of stairs has been shown to deter some people from climbing.

Witt also argued that more psychologists should take a nuanced view of vision and perception than they currently do. “We think perception is this window to the actual physical world,” she said. “Those assumptions that drive most of the field are wrong.”

She also alluded to tangential but supporting studies to the premise that an ability to act affects unconscious perceptions. People holding guns are more likely to see guns in the hands of other people, even when that person is holding a shoe, for instance, and guns and images of guns have also been shown to make people feel more fear and anger.