In 4 experiments, it was shown that hills appear steeper to people who are encumbered by wearing a heavy backpack (Experiment 1), are fatigued (Experiment 2), are of low physical fitness (Experiment 3), or are elderly and/or in declining health (Experiment 4). Visually guided actions are unaffected by these manipulations of physiological potential. Although dissociable, the awareness and action systems were also shown to be interconnected. Recalibration of the transformation relating awareness and actions was found to occur over long-term changes in physiological potential (fitness level, age, and health) but not with transitory changes (fatigue and load). Findings are discussed in terms of a time-dependent coordination between the separate systems that control explicit visual awareness and visually guided action.In conscious awareness, the apparent slant of hills is greatly exaggerated. For example, 5° hills appear to be about 20°, and 10° ones look to be about 30° (Proffitt, Bhalla, Gossweiler, & Midgett, 1995). Be that as it may, people are not especially prone to stumble whenever the terrain over which they walk changes in slant. When ascending a 5° hill, people appropriately raise their feet to accommodate this incline, not a 20° one.In this and our previous article (Proffitt et al., 1995), we suggest that the exaggeration of slant in conscious awareness promotes the function of relating distal inclines to one's physiological potential. Given gravity and one's physiology, a long 5° hill is actually rather difficult to ascend, and consequently it appears to be quite steep. Given this proposal, we predict that geographical slant will change with changes in physiological potential.The first purpose of this article is to provide support for this prediction. In four experiments, we show that hills appear steeper when people are (a) encumbered by wearing a heavy backpack, (b) fatigued after a long run, (c) of low physical fitness, and (d) elderly or in poor health. None of

Perception informs people about the opportunities for action and their associated costs. To this end, explicit awareness of spatial layout varies not only with relevant optical and ocular-motor variables, but also as a function of the costs associated with performing intended actions. Although explicit awareness is mutable in this respect, visually guided actions directed at the immediate environment are not. When the metabolic costs associated with walking an extent increase—perhaps because one is wearing a heavy backpack—hills appear steeper and distances to targets appear greater. When one is standing on a high balcony, the apparent distance to the ground is correlated with one's fear of falling. Perceiving spatial layout combines the geometry of the world with behavioral goals and the costs associated with achieving these goals.

People judged the inclination of hills viewed either out-of-doors or in a computer-simulated virtual environment. Anglejudgments were obtained by having people (1) provide verbal estimates, (2) adjust a representation of the hill's cross-section, and (3) adjust a tilt board with their unseen hand. Geographical slant was greatly overestimated according to the first two measures, but not the third. Apparent slant judgments conformed to ratio scales, thereby enhancing sensitivity to the small inclines that must actually be traversed in everyday experience. It is proposed that the perceived exaggeration of geographical slant preserves the relationship between distal inclination and people's behavioral potential. Hills are harder to traverse as people become tired; hence, apparent slant increased with fatigue. Visuallyguided actions must be accommodated to the actual distal properties of the environment; consequently, the tilt board adjustments did not reflect apparent slant overestimations, nor were they influenced by fatigue. Consistent with the fact that steep hills are more difficult to descend than to ascend, these hills appeared steeper when viewed from the top.By east coast standards, Virginia is a mountainous state, and many of its roads appear quite steep, especially to midwestern visitors. Yet by law, roads in the state can be inclined no more than 9°from the horizontal, and 9°is a much smaller angle than the inclination that most people estimate these steep roads to have. This is an example ofa pervasive phenomenon: Hills appear to be steeper than they actually are. The first purpose of this paper is to provide a normative description of this overestimation in geographical slant perception.As we will show, a 5°hill is typically judged to be almost 20°in slant; however, when walking up a 5°hill, we do not raise our feet to accommodate a 20°incline and thereby stumble as we begin the ascent. The visual guidance oflocomotion shows no evidence of slant misperception. The second purpose of this paper is to show that a motoric index of geographical slant shows little evidence of the overestimations manifest in visual awareness. The paper's third purpose may be introduced with an anecdote.Not long ago, I (Proffitt) was riding in a l-day, 100-mile, bicycle tour, with the finish-line only a couple of miles ahead. The tour had traversed a number ofsmall mountains in a circuit that began and ended at a site in the rolling hills of the Virginia piedmont. The final hill before the finish seemed incredibly steep, and as I passed another rider I commented on how organizers of these affairs always seemed to arrange for the steepest hills to be located just before the finish. The other rider muttered an oath as she bemoaned what a cruel joke it was to make us climb this hill so late in the ride. (It would have been an even crueler joke to have informed her that the incline of this hill was only about r.) Now the hill in question was relatively steep, but it was far less so than many that we had previously encountered durin...

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.

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.

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.

Perception is influenced by the perceiver’s ability to perform intended actions. For example, when people intend to reach with a tool to targets that are just beyond arm’s reach, the targets look closer than when they intend to reach without the tool (Witt, Proffitt, & Epstein, 2005). This is one of several examples demonstrating that behavioral potential affects perception. However, the action-specific processes that are involved in relating the person’s abilities to perception have yet to be explored. Four experiments are presented that implicate motor simulation as a mediator of these effects. When a perceiver intends to perform an action, the perceiver runs a motor simulation of that action. The perceiver’s ability to perform the action, as determined by the outcome of the simulation, influences perceived distance.

Six experiments compared spatial updating of an array after imagined rotations of the array versus viewer. Participants responded faster and made fewer errors in viewer tasks than in array tasks while positioned outside (Experiment 1) or inside (Experiment 2) the array. An apparent array advantage for updating objects rather than locations was attributable to participants imagining translations of single objects rather than rotations of the array (Experiment 3). Superior viewer performance persisted when the array was reduced to 1 object (Experiment 4); however, an object with a familiar configuration improved object performance somewhat (Experiment 5). Object performance reached near-viewer levels when rotations included haptic information for the turning object. The researchers discuss these findings in terms of the relative differences in which the human cognitive system transforms the spatial reference frames corresponding to each imagined rotation.Suppose you are playing a board game with a group of friends, and you want to know what the board looks like from one of their perspectives, without moving to it. There are two obvious ways to proceed. You could imagine rotating the board until the side corresponding to the new perspective is coincident with your current viewpoint (object rotation). Alternatively, you could imagine moving yourself to the vantage point of the new perspective (viewer rotation). Both operations have been implicated in human beings 1 ability to update objects and scenes across views (e.g.,