The accuracy of 'haptically' measured geographical slant perception

Interrupting Pedestrians in Indonesia; Effect of Climate on Perceived Steepness and Stair Climbing Behaviour

Increased activity during daily life is one public health initiative to reduce population inactivity. Increasing temperature and humidity influence walking for transport by reducing the blood supply available to exercising muscles. This study investigated effects of temperature and humidity on a perceptual cue, estimated stair slant, that can influence behaviour, and on subsequent speed of climbing. Participants (402 males, 423 females) estimated the slant of a 20.4° staircase at a university in Indonesia. Subsequently, the participants were timed covertly while climbing. As temperature and humidity increased, estimated stair slant became more exaggerated. Females estimated stair slant as steeper than males. For stair climbing, speed was reduced as temperature increased, and females climbed slower than males. Estimates of stair slant were not associated with speed of the subsequent climb. Climate influences estimates of stair slant that precede stair climbing and subsequent speed of the ascent. In this study, perception was unrelated to behaviour.

The differential effects of task difficulty on the perception of passing distance and subsequent passing action in a field hockey push pass task

The aims of the study were to initially investigate whether the perceived distance of a field hockey push pass task was influenced by manipulating task difficulty (Experiment 1), and further, expanding on the research, whether perceptual biases would translate into the execution of a corresponding push pass action (Experiment 2). Based on predictions from the two-visual systems model, we hypothesized that the action-specific perceptual biases in distance perception would not translate into the control of movement. In Experiment 1, elite field hockey players estimated the distance from targets that differed in size before making push pass actions toward the target (i.e., the smaller targets being more difficult). Results showed that participants did estimate the perceived distance of the push pass task to be larger as a function of task difficulty. We found a similar result in Experiment 2, and in addition, manipulated the required outcome of the push-pass while measuring the speed of the push-pass and found that a perceptual bias did not translate into the execution of the actual push pass task (Experiment 2). In line with the action-specific account of perception, a perceptual bias arose that may assist in making adaptive action choices. However, consistent with the two-visual systems model, this perceptual bias did not affect subsequent control of movement, preventing it from becoming maladaptive. Implications for talent identification and development are briefly discussed.

Palm board and verbal estimates of slant reflect the same perceptual representation

People verbally overestimate the orientation of slanted surfaces, but accurately estimate or underestimate slanted surfaces using a palm board. We demonstrate a fundamental issue that explains why the two different values typically given for palm board and verbal/visual matching estimates express similar perceptual representations of slanted surfaces. The fundamental problem in studies measuring palm board and verbal estimates is that the "measure"-either (1) reproducing a verbally given angle or the orientation of a slanted surface with an unseen hand or (2) verbally or visually estimating a visually perceived surface-has always been confounded with the "surface"-either using (1) a palm board or (2) a hill or ramp. Although reproduction has exclusively been used with palm boards in these studies, at the same time verbal estimation or visual matching has exclusively been used with hills/ramps. In three experiments, we showed that verbally estimating palm board orientations produces overestimates by a factor of 1.5, whereas reproducing the orientation of the surface of a ramp to verbally given angles produces gains of ~0.6. These values are similar to those seen for verbal overestimates of slanted surfaces, and to palm board gains for near surfaces and the relative palm-board-to-verbal gains for outdoor hills, respectively. Eliminating this confound eliminated the difference previously seen across surfaces. We discuss how and why different measures should produce different results if we overestimate slant in general and perceptually represent slant in the same way, both haptically and visually.

Manual anchoring biases in slant estimation affect matches even for near surfaces

People verbally overestimate hill slant by ~15°-25°, whereas manual estimates (e.g., palm board measures) are thought to be more accurate. The relative accuracy of palm boards has contributed to the widely cited theoretical claim that they tap into an accurate, but unconscious, motor representation of locomotor space. Recently, it was shown that a bias that stems from anchoring the hand at horizontal prior to the estimate can quantitatively account for the difference between manual and verbal estimates of hill slant. The present work extends this observation to manual estimates of near-surface slant, to test whether the bias derives from manual or visual uncertainty. As with far surfaces, strong manual anchoring effects were obtained for a large range of near-surface slants, including 45°. Moreover, correlations between participants' manual and verbal estimates further support the conclusion that both measures are based on the same visual representation.

Perception of Stand-on-ability: Do Geographical Slants Feel Steeper Than They Look?

Past research has shown that haptically perceived surface slant by foot is matched with visually perceived slant by a factor of 0.81. Slopes perceived visually appear shallower than when stood on without looking. We sought to identify the sources of this discrepancy by asking participants to judge whether they would be able to stand on an inclined ramp. In the first experiment, visual perception was compared to pedal perception in which participants took half a step with one foot onto an occluded ramp. Visual perception closely matched the actual maximal slope angle that one could stand on, whereas pedal perception underestimated it. Participants may have been less stable in the pedal condition while taking half a step onto the ramp. We controlled for this by having participants hold onto a sturdy tripod in the pedal condition (Experiment 2). This did not eliminate the difference between visual and haptic perception, but repeating the task while sitting on a chair did (Experiment 3). Beyond balance requirements, pedal perception may also be constrained by the limited range of motion at the ankle and knee joints while standing. Indeed, when we restricted range of motion by wearing an ankle brace pedal perception underestimated the affordance (Experiment 4). Implications for ecological theory were offered by discussing the notion of functional equivalence and the role of exploration in perception.

Does perceived steepness deter stair climbing when an alternative is available?

Perception of hill slant is exaggerated in explicit awareness. Proffitt (Perspectives on Psychological Science 1:110–122, 2006) argued that explicit perception of the slant of a climb allows individuals to plan locomotion in keeping with their available locomotor resources, yet no behavioral evidence supports this contention. Pedestrians in a built environment can often avoid climbing stairs, the man-made equivalent of steep hills, by choosing an adjacent escalator. Stair climbing is avoided more by women, the old, and the overweight than by their comparators. Two studies tested perceived steepness of the stairs as a cue that promotes this avoidance. In the first study, participants estimated the steepness of a staircase in a train station (n = 269). Sex, age, height, and weight were recorded. Women, older individuals, and those who were heavier and shorter reported the staircase as steeper than did their comparison groups. In a follow-up study in a shopping mall, pedestrians were recruited from those who chose the stairs and those who avoided them, with the samples stratified for sex, age, and weight status. Participants (n = 229) estimated the steepness of a life-sized image of the stairs they had just encountered, presented on the wall of a vacant shop in the mall. Pedestrians who avoided stair climbing by choosing the escalator reported the stairs as steeper even when demographic differences were controlled. Perceived steepness may to be a contextual cue that pedestrians use to avoid stair climbing when an alternative is available.

Summarizing slant perception with words and hands; an empirical alternative to correlations in Shaffer, McManama, Swank, Williams & Durgin (2014)

The paper by Shaffer, McManama, Swank, Williams & Durgin (2014) uses correlations between palm-board and verbal estimates of geographical slant to argue against dissociation of the two measures. This paper reports the correlations between the verbal, visual and palm-board measures of geographical slant used by Proffitt and co-workers as a counterpoint to the analyses presented by Shaffer and colleagues. The data are for slant perception of staircases in a station (N=269), a shopping mall (N=229) and a civic square (N=109). In all three studies, modest correlations between the palm-board matches and the verbal reports were obtained. Multiple-regression analyses of potential contributors to verbal reports, however, indicated no unique association between verbal and palm-board measures. Data from three further studies (combined N=528) also show no evidence of any relationship. Shared method variance between visual and palm-board matches could account for the modest association between palm-boards and verbal reports.

Anchoring in action: manual estimates of slant are powerfully biased toward initial hand orientation and are correlated with verbal report

People verbally overestimate hill slant by approximately 15° to 25°, whereas manual estimates (e.g., palm board measures) are thought to be more accurate. The relative accuracy of palm boards has contributed to the widely cited theoretical claim that they tap into an accurate, but unconscious, motor representation of locomotor space. In the current work, 4 replications (total N = 204) carried out by 2 different laboratories tested an alternative anchoring hypothesis that manual action measures give low estimates because they are always initiated from horizontal. The results of all 4 replications indicate that the bias from response anchoring can entirely account for the difference between manual and verbal estimates. Moreover, consistent correlations between manual and verbal estimates given by the same observers support the conclusion that both measures are based on the same visual representation. Concepts from the study of judgment under uncertainty apply even to action measures in information rich environments.

What hands know about objects; taking perception of hills out of context: a response to Durgin (2013)

In a recent paper, we provided independent evidence on the accuracy of 'haptically' measured geographical slant perception (Taylor-Covill & Eves, 2013). Durgin (2013) argues that the devices used in our work, namely the palm-board, and palm-controlled inclinometer (PCI), are not measures of perception. In response, we outline four failures of replication in the laboratory work of Durgin and colleagues on which they base their model of slant perception. We also highlight fundamental differences between the perceptual tasks Durgin and colleagues ask of participants relative to those of Proffitt and colleagues' traditional measures. These subtle differences might help explain how the two groups have arrived at discrepant conclusions.

What do hands know about hills? Interpreting Taylor-Covill and Eves (2013) in context

Hills appear much steeper than they are. Although near surface slant is also exaggerated, near surfaces appear much shallower than equivalently slanted hills. Taylor-Covill and Eves (2013) propose a new type of palm orientation measuring device that provides outputs that accurately reflect the physical slants of stairs and hills from 19 to 30° and also seems to accurately reflect the slants of near surfaces (25-30°). They question the validity of the observations of Durgin, Hajnal, Li, Tonge & Stigliani (2010), who observed that palm boards grossly underestimated near surfaces. Here I review our recent work on the visual and haptic perception of near surface orientation in order to place Taylor-Covill and Eves' arguments in context. I note in particular that free hand measures of real surfaces in near space show excellent calibration, but free hand measures show gross exaggeration for hills. This leads to the question of the grounds for preferring a mechanical device to a freely wielded hand. In addition I report an investigative replication of the crucial observations that led to our concerns about the value of palm boards as measures of perception and note the specific methodological details that we have accounted for in our procedures. Finally, I propose some testable hypotheses regarding how better-than-expected haptic matches to hills may arise.

Slant perception for stairs and screens: effects of sex and fatigue in a laboratory environment

The apparent slope of a hill or staircase, termed geographical slant perception, is exaggerated in explicit awareness. Across two experiments this paper tests the use of a laboratory environment to study geographical slant perception. First, using a student-aged sample (N = 166), we examine the similarity of slant estimates in the field with those made in the laboratory using life-sized images of the built environment as stimuli. Results reveal no differences in slant estimates between the two test environments. Furthermore, three traditional measures of perceived geographical slant (verbal, visual, and haptic) appear sensitive to a difference in slant of only 3.4 degrees in both the field and laboratory environments. In a follow-up experiment we test the effect of fatigue on slant estimates in the laboratory. In line with previous research with outdoor stimuli, fatigued participants provided more exaggerated explicit reports of slant relative to those in a control group, and females gave more exaggerated slant estimates than males across both experiments. The current set of findings open the door to future studies of geographical slant perception that may be more suited to laboratory conditions.