When walking effort is increased due to manipulations such as wearing heavy backpacks, people perceive hills to be steeper and distances to be farther (Bhalla & Proffitt, 1999; Proffitt, Stefanucci, Banton, & Epstein, 2003). On the basis of these findings, we expected people to overestimate distances on steep hills relative to the same distances on flat ground, because of the increased effort required to ascend or descend them. This hypothesis is in contrast to the belief that distances are specified solely by optical and oculomotor information related to the geometry of the environment. To test the hypothesis, we investigated distance estimation on hills and flat terrains in natural and virtual environments. We found that participants judged steep uphill and downhill distances to be farther than the same distances on flat terrain. These results are inconsistent with the idea that spatial layout is perceived solely in terms of geometry, lending partial support to an effort hypothesis.

The literature on intuitive physics shows that many people exhibit systematic errors when predicting the behavior of simple physical events. Most previous research has attributed these errors to factors specific to a certain class of tasks. In the present study, we investigated the possibility that intuitive physics performance may be related to general measures of cognitive ability. Two hundred four adults (ages, 20-91 years) were presented with five pairs of intuitive physics questions. It was found that performance on the intuitive physics items was moderately intercorrelated, suggesting that they were tapping into a unitary construct. Despite the correlation with factors that decline with advancing age, intuitive physics performance was not correlated with age (r= .00). The findings are discussed in the context of research on intuitive physics, as well as research on cognitive aging.

Recent research demonstrates neurologic and behavioral differences in people's responses to the space that is within and beyond reach. The present studies demonstrated a perceptual difference as well. Reachability was manipulated by having participants reach with and without a tool. Across 2 conditions, in which participants either held a tool or not, targets were presented at the same distances. Perceived distances to targets within reach holding the tool were compressed compared with targets that were beyond reach without it. These results suggest that reachability serves as a metric for perception. The 3rd experiment found that reachability only influenced perceived distance when the perceiver intended to reach. These experiments suggest that the authors perceive the environment in terms of our intentions and abilities to act within it.

Baseball players frequently say that the ball appears bigger when they are hitting well. In describing a mammoth 565-ft home run, Mickey Mantle said, “I never really could explain it. I just saw the ball as big as a grapefruit” (Early, n.d.). George Scott of the Boston Red Sox said, “When you're hitting the ball [well], it comes at you looking like a grapefruit. When you're not, it looks like a blackeyed pea” (Baseball Almanac, n.d.). During a slump, Joe “Ducky” Medwick of the St. Louis Cardinals said he felt like he was “swinging at aspirins” (Bradley, 2003). Similar comments have been made by such Hall of Famers as Ted Williams (Bicknell, 2000), “Wee” Willie Keeler (Bradley, 2003), George Brett (Langill, n.d.), and more.

This phenomenon is not limited to baseball. When playing well, tennis players report that the ball looks huge, golfers say that the cup looks bigger, and basketball players say that the hoop looks enormous. All of these people report perceptions that are modulated by performance efficacy. Our experiment confirms that this phenomenon is a psychological reality.

In four experiments, we examined observers’ ability to locate objects in virtual displays while rotating to new perspectives. In Experiment 1, participants updated the locations of previously seen landmarks in a display while rotating themselves to new views (viewer task) or while rotating the display itself (display task). Updating was faster and more accurate in the viewer task than in the display task. In Experiment 2, we compared updating performance during active and passive self-rotation. Participants rotated themselves in a swivel chair (active task) or were rotated in the chair by the experimenter (passive task). A minimal advantage was found for the active task. In the final experiments, we tested similar manipulations with an asymmetrical display. In Experiment 3, updating during the viewer task was again superior to updating during the display task. In Experiment 4, we found no difference in updating between active and passive self-movement. These results are discussed in terms of differences in sources of extraretinal information available in each movement condition.

Perceiving egocentric distance is not only a function of the optical variables to which it relates, but also a function of people's current physiological potential to perform intended actions. In a set of experiments, we showed that, as the effort associated with walking increases, perceived distance increases if the perceiver intends to walk the extent, but not if the perceiver intends to throw. Conversely, as the effort associated with throwing increases, perceived distance increases if people intend to throw to the target, but not if they intend to walk. Perceiving distance combines the geometry of the world with our behavior goals and the potential of our body to achieve these goals.

Berkeley proposed that space is perceived in terms of effort. Consistent with his proposal, the present studies show that perceived egocentric distance increases when people are encumbered by wearing a heavy backpack or have completed a visual-motor adaptation that reduces the anticipated optic flow coinciding with walking effort. In accord with Berkeley's proposal and Gibson's theory of affordances, these studies show that the perception of spatial layout is influenced by locomotor effort.

One important aspect of the pictorial representation of a scene is the depiction of object proportions. Yang, Dixon, and Proffitt (1999 Perception 28 445–467) recently reported that the magnitude of the vertical – horizontal illusion was greater for vertical extents presented in three-dimensional (3-D) environments compared to two-dimensional (2-D) displays. However, because all of the 3-D environments were large and all of the 2-D displays were small, the question remains whether the observed magnitude differences were due solely to the dimensionality of the displays (2-D versus 3-D) or to the perceived distal size of the extents (small versus large). We investigated this question by comparing observers' judgments of vertical relative to horizontal extents on a large but 2-D display compared to the large 3-D and the small 2-D displays used by Yang et al (1999). The results confirmed that the magnitude differences for vertical over-estimation between display media are influenced more by the perceived distal object size rather than by the dimensionality of the display.