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When making decisions about uncertain spatial trajectories, such as storm forecasts, people rely on visualizations to support their understanding. Four experiments explored novel visualizations-dynamic ensembles. Nonexperts used visualizations to interpret probabilistic information about potential paths of a hurricane. Experiment 1 focused on global properties of the distribution, and showed dynamic ensembles imply a larger area at risk than traditional cones of uncertainty. Experiment 2 compared decisions with cones versus dynamic ensembles at specific individual locations. Dynamic ensembles offer more appreciation of risk outside the center of the distribution, and less abrupt in transitions from evacuation to nonevacuation choices. Experiment 3 compared decisions for dynamic ensembles versus static line ensembles. Similar evacuation rates across the two conditions suggest ensembles, rather than dynamics, are the more critical feature. Experiment 4 examined whether an additional dimension can be included in dynamic ensembles using color coding. Decisions reacted to this ancillary feature, with higher evacuation rates for locations threatened by more severe outcomes. Outcomes highlight the ability to systematically vary the level of risk communicated through the ensembles while also communicating the continuous nature of the risk. The overall findings show the viability of presenting uncertain spatial information using dynamic ensembles. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Dynamic ensemble visualizations might effectively convey the future path of an approaching tropical storm, and they offer benefits over commonly used Cones of Uncertainty. This experiment examined perceptions of risk at coastal locations of varying eccentricity from the most likely forecast path of a hypothetical hurricane. Perceptions of high (need to evacuate) and moderate (need to prepare) risk from inbound storms dropped off dramatically for Cone of Uncertainty visualizations, consistent with the influence of a containment effect induced by the cone’s boundary line. In contrast, Animated Risk Trajectories offered a more continuous sense of declining risk with distance, and much higher rates of needing to prepare at larger eccentricities that while at lower risk would still be vulnerable to some potential future paths. The findings lend further support to the viability of Animated Risk

Hurricane forecasts are often communicated through visualizations depicting the possible future track of the storm. The Cone of Uncertainty (COU) is a commonly used visualization, but the graphic is prone to misinterpretation such as thinking only locations contained within the cone’s boundary are at risk. In this study, we investigated the utility of conveying hurricane forecast tracks using a set of animated icons, each representing an instance of a possible storm path. We refer to this new visualization as Animated Risk Trajectories (ARTs). We measured non-experts’ perception of risk when viewing simplified, hypothetical hurricane forecasts presented as ARTs or COUs. To measure perception of risk for each visualization type, we designed experiments to have participants make decisions to evacuate individual towns at varying distances from the most likely forecast path of a storm. The ARTs led to greater risk perception in areas that fell beyond the cone’s boundaries. Non-experts’ interpretation of risk was impacted by the visual properties of the ARTs, such as the distribution of the icons, including their density and whether the distribution was unimodal or bimodal. This supports the suggestion that ARTs can have value in communicating spatial-temporal uncertainty.

Humanity is facing our greatest challenge ever: to address run-away global temperatures and ecosystem degradation threatening civilization as we know it. Human factors and ergonomics have much to contribute in partnering with industry, government, academia, and society as a whole, to stop the destruction of our home, and evolve systems to sustainably provide clean energy and other resources needed to feed, clothe, house, sanitize, and transport humans. In this poster, we present a sampling of ways ergonomists, human factors researchers, and practitioners are already engaging in work to support environmental sustainability, as well as areas in which HFE could be applied to support progress toward sustainability goals. Examples presented include contributions from members of the HFES Sustainability Task Force. We share this with the HFES community both to inform work completed and in-progress as well as to inspire the participation of others in this important work.

Scatterplots can encode a third dimension by using additional channels like size or color (e.g. bubble charts). We explore a potential misinterpretation of trivariate scatterplots, which we call the weighted average illusion, where locations of larger and darker points are given more weight toward x- and y-mean estimates. This systematic bias is sensitive to a designer's choice of size or lightness ranges mapped onto the data. In this paper, we quantify this bias against varying size/lightness ranges and data correlations. We discuss possible explanations for its cause by measuring attention given to individual data points using a vision science technique called the centroid method. Our work illustrates how ensemble processing mechanisms and mental shortcuts can significantly distort visual summaries of data, and can lead to misconceptions like the demonstrated weighted average illusion.

Communication regarding COVID-19 vaccines requires evidence-based strategies. We present findings from a quantitative survey measuring participants’ understanding, trust, and decision-making in response to information conveying low or high uncertainty regarding the vaccine. Communication conveying high uncertainty led to lower self-assessed understanding but higher actual understanding of possible outcomes. Communication conveying low uncertainty increased vaccine acceptance by those who previously opposed vaccines. This indicates that communicating uncertainty may have different effects over time and that adjusting messaging depending on audiences’ prior vaccine attitudes might be important. These findings support the need for further investigation of how uncertainty communication influences vaccine acceptance.

While visualization can support understanding complex phenomena, their effectiveness might vary with the recipient’s familiarity with both the phenomenon and the visualization. The current study contrasted interpretations of simulated hurricane paths using student populations from a high frequency hurricane area versus no local hurricane risk. Non-expert understanding of trajectory predictions was supported via two visualizations: common cones of uncertainty and novel dynamic ensembles. General patterns of performance were similar across the two groups. Participants from the high hurricane risk area did show narrower decision thresholds, in both common and novel visualization formats. More variability was consistently considered possible when viewing the dynamic ensemble displays. Despite greater likelihood of experiences with variability of trajectories outside of forecast paths, greater familiarity tended towards narrower interpretations of the need for evacuations within the variability possible. The results suggest an advantage of dynamic ensembles in grasping uncertainty even in populations familiar with hurricanes.

Visualizations attempt to convey the uncertain track of an approaching hurricane. The current experiment contrasted decision characteristics that resulted from observing hurricane paths presented using cones of uncertainty versus a new form of dynamic ensemble. Participants made judgments about whether to evacuate a town at different eccentricities to the central predicted path of a storm. Results showed that dynamic ensembles have different properties to cone displays. Presentations of dynamic ensembles encouraged greater consideration of evacuation at locations further from the most probable path, but that were still at risk. However, dynamic ensembles resulted in lower evacuation rates at the center of the distribution, consistent with a probabilistic sense of the risk but nonetheless a potentially undesirable strategy. In addition, perceptions of the evacuation need with dynamic ensemble presentations were more strongly influenced by the amount of variability than with cones. The implications for use of dynamic ensembles are discussed.

The action-specific account of perception suggests that our perceptual system is influenced by information about our ability to act in our environment and, thus, affects our perception. However, the specific information about action that is influential for perception is still largely unknown. For example, if a goal is achieved through automation rather than action, is perception influenced because the goal was achieved or is perception immune because the act was automated rather than performed by the observer? In four experiments, we examined whether automating a paddle to block a moving ball in a computer game similar to Pong affects perception of the ball's speed. Results indicate that the automation used here did not affect speed perception of the target. Whereas tools such as reach-extending sticks and various-sized paddles are both incorporated into one's body schema and also influence spatial perception, automation, our results imply that automation is not incorporated into one's body schema and does not affect spatial perception. The dissociation in how the mind treats tools versus automation could have several implications as automation becomes more prevalent in daily life.

Despite the impression that perception of spatial layout including distance, slant, and size is objective and geometrically accurate, spatial perception is influenced by a perceiver's ability to act. Hills appear steeper when the perceiver is fatigued, and balls appear faster when they are harder to block. The same environment looks different when the perceiver is better able to act than when actions are constrained. Claims of action's influence on spatial perception have been met with much controversy, and spurred many experiments designed to explore alternative explanations. In at least one case, these alternative explanations have failed to account for action's effect, thereby leading to the conclusion that the potential for action can truly influence spatial perception. The mystery remains, however, as to how action exerts its influence.

Design plays a key role in the interpretability of complex visualizations. Many applied domains utilize large quantities of data to make predictions, ranging from maps showing the spread of infectious disease to line graphs displaying global temperature changes. These visualizations tap into the visual system's ability to extract information from groups of similar objects, a process known as ensemble processing, and the cognitive system's ability to relate visual features such as color to meaningful concepts such as disease or temperature. Visualizations must consider both perceptual and cognitive abilities. It remains unclear which best improves comprehension: visualizations designed to exploit ensemble processes or that use semantically resonant colors that align with the underlying data. To address this question, participants were shown visualizations designed for ensemble processes in that they used color encodings with only a single hue or designed for semantic processes in that they prioritized color alignment with the meaning of the data. Participants viewed stripplots using these colors and judged whether the temperature depicted in the graphs was increasing or decreasing. As quantified using the signal detection measure

PURPOSE: Diagnosing breast cancer based on the distribution of calcifications is a visual task and thus prone to visual biases. We tested whether a recently discovered visual bias that has implications for breast cancer diagnosis would be present in expert radiologists, thereby validating the concern of this bias for accurate diagnoses. APPROACH: We ran a vision experiment with expert radiologists and untrained observers to test the presence of visual bias when judging the spread of dots that resembled calcifications and when judging the spread of line orientations. We calculated visual bias scores for both groups for both tasks. RESULTS: Participants overestimated the spread of the dots and the spread of the line orientations. This bias, referred to as the variability overestimation effect, was of similar magnitudes in both expert radiologists and untrained observers. Even though the radiologists were better at both tasks, they were similarly biased compared with the untrained observers. CONCLUSIONS: The results justify the concern of the variability overestimation effect for accurate diagnoses based on breast calcifications. Specifically, the bias is likely to lead to an increased number of false-negative results, thereby leading to delayed treatments.

Understanding the variability of trends and other continuously distributed quantities is a vital ability underlying many safety critical decisions, such as how widely to search for a downed aircraf...

Science is often perceived to be a self-correcting enterprise. In principle, the assessment of scientific claims is supposed to proceed in a cumulative fashion, with the reigning theories of the day progressively approximating truth more accurately over time. In practice, however, cumulative self-correction tends to proceed less efficiently than one might naively suppose. Far from evaluating new evidence dispassionately and infallibly, individual scientists often cling stubbornly to prior findings. Here we explore the dynamics of scientific self-correction at an individual rather than collective level. In 13 written statements, researchers from diverse branches of psychology share why and how they have lost confidence in one of their own published findings. We qualitatively characterize these disclosures and explore their implications. A cross-disciplinary survey suggests that such loss-of-confidence sentiments are surprisingly common among members of the broader scientific population yet rarely become part of the public record. We argue that removing barriers to self-correction at the individual level is imperative if the scientific community as a whole is to achieve the ideal of efficient self-correction. ispartof: PERSPECTIVES ON PSYCHOLOGICAL SCIENCE vol:16 issue:6 pages:1255-1269 ispartof: location:United States status: published

Visual perception is not always veridical but can be influenced by factors such as ease of acting, energetic cost, and even body type of the observer. This notion is called action-specific perception. Several effects of action capability on visual perception have been found, but there is much controversy as to whether these effects are truly perceptual. Because perception cannot be measured directly, resolving the controversy relies on ruling out alternative explanations through systematic testing. We combined one of the most robust action-specific effects (the Pong effect) with one of the primary suggestions for exploring an alternative explanation, namely whether the effect persists across instructions that emphasize different aspects of the task. The Pong effect was robust to the type of instructions. The results provide critical evidence that the Pong effect is truly perceptual, furthering the argument that a person’s ability to act can influence visual perception.

Risk communication is critically important, for both patients and providers. However, people struggle to understand risks because there are inherent biases and limitations to reasoning under uncertainty. A common strategy to enhance risk communication is the use of decision aids, such as charts or graphs, that depict the risk visually. A problem with prior research on visual decision aids is that it used a metric of performance that confounds 2 underlying constructs: precision and bias. Precision refers to a person’s sensitivity to the information, whereas bias refers to a general tendency to overestimate (or underestimate) the level of risk. A visual aid is effective for communicating risk only if it enhances precision or, once precision is suitably high, reduces bias. This article proposes a methodology for evaluating the effectiveness of visual decision aids. Empirical data further illustrate how the new methodology is a significant advancement over more traditional research designs.

The gun embodiment effect is the consequence caused by wielding a gun on judgments of whether others are also holding a gun. This effect could be responsible for real-world instances when police officers shoot an unarmed person because of the misperception that the person had a gun. The gun embodiment effect is an instance of embodied cognition for which a person’s tool-augmented body affects their judgments. The replication crisis in psychology has raised concern about embodied cognition effects in particular, and the issue of low statistical power applies to the original research on the gun embodiment effect. Thus, the first step was to conduct a high-powered replication. We found a significant gun embodiment effect in participants’ reaction times and in their proportion of correct responses, but not in signal detection measures of bias, as had been originally reported. To help prevent the gun embodiment effect from leading to fatal encounters, it would be useful to know whether individuals with certain traits are less prone to the effect and whether certain kinds of experiences help alleviate the effect. With the new and reliable measure of the gun embodiment effect, we tested for moderation by individual differences related to prior gun experience, attitudes, personality, and factors related to emotion regulation and impulsivity. Despite the variety of these measures, there was little evidence for moderation. The results were more consistent with the idea of the gun embodiment effect being a universal, fixed effect, than being a flexible, malleable effect.

Action-specific effects, such as a fish appearing faster when it is harder to catch, have been primarily demonstrated using explicit perceptual judgments. These sorts of judgments rely on the cognitive or “what” visual pathway. An open question is whether action-specific effects also influence the action pathway. If fish look faster when the net is small, the net should be released earlier than when the net is big. Previously, this action measure was always paired with an explicit measure of fish speed, which is known to evoke the cognitive visual pathway. Here, net release time was examined without any explicit judgments. The action-specific effect of net size still emerged. Assuming net release time taps into the action pathway, the current studies provide support that action-specific effects occur within both the cognitive and action pathways, possibly because these effects operate on early visual processes prior to the split between the two pathways.

Studies that consider attitudes towards guns have unilaterally relied on scales that treat guns as autonomous objects. The Gun Attitude Scale (GAS), development and replication results reported herein, takes into account one’s comfort with gun use. Exploratory factor analysis results indicated and confirmatory factor analysis confirmed, χ2 = 96.64, df = 26, p

According to the action-specific account of perception, people perceive the spatial layout of the environment in relation to their ability to act. Pioneering research by Bhalla and Proffitt (1999) demonstrated that hills were judged as steeper to perceivers with less physiological potential. Since this seminal work, much research has shown these action-specific effects generalize beyond hill slant perception and beyond physiological potential, but the underlying mechanisms are underspecified. The present experiments explore the potential mechanism that information about action is integrated with visual information about the target. According to an integration account, information from various sources are weighted, and the strength of these weights dictates the strength of that source of information on the resulting percept. One prediction is that it should be possible to vary the strength of the weights and thereby vary the size of a particular effect. To reduce the effect of action on perception, control over the action was taken away from participants. As predicted, losing control reduced the impact of action on spatial perception. This is the first reported instance of a partial action-specific effect, and is consistent with an integration-based mechanism. (PsycINFO Database Record

A critical question for theories of spatial vision concerns the nature of the inputs to perception. The action-specific account asserts that information related to action, specifically a perceiver's ability to perform the intended action, is one of these sources of information. This claim challenges assumptions about the mind in general and perception in particular, and not surprisingly, has been met with much resistance. Alternative explanations include that these effects are due to response bias, rather than genuine differences in perception. Using a paradigm in which ease to block a ball impacts estimated speed of the ball, participants were given explicit feedback about their perceptual judgements to test the response bias alternative. Despite the feedback, the action-specific effect still persisted, thus ruling out a response-bias interpretation. Coupled with other research ruling out additional alternative explanations, the current findings offer an important step towards the claim that a person's ability to act truly influences spatial perception.

Graphs are an effective and compelling way to present scientific results. With few rigid guidelines, researchers have many degrees-of-freedom regarding graph construction. One such choice is the range of the y-axis. A range set just beyond the data will bias readers to see all effects as big. Conversely, a range set to the full range of options will bias readers to see all effects as small. Researchers should maximize congruence between visual size of an effect and the actual size of the effect. In the experiments presented here, participants viewed graphs with the y-axis set to the minimum range required for all the data to be visible, the full range from 0 to 100, and a range of approximately 1.5 standard deviations. The results showed that participants’ sensitivity to the effect depicted in the graph was better when the y-axis range was between one to two standard deviations than with either the minimum range or the full range. In addition, bias was also smaller with the standardized axis range than the minimum or full axis ranges. To achieve congruency in scientific fields for which effects are standardized, the y-axis range should be no less than 1 standard deviations, and aim to be at least 1.5 standard deviations.

What is the perceptual experience of variability? Unconscious perceptual processes are well-calibrated to variability, as are unconscious motor processes, whereas cognitive processes are not well-calibrated and tend to underestimate variability. Regarding the perceptual experience of variability, perceivers are sensitive to differences in the variability of ensembles of objects, but any potential biases have not yet been explored. In the current experiments, participants viewed a set of lines at various orientations that were presented 1 at a time in a random order. Participants judged whether the orientations within each set were more similar to each other or more disperse. Although participants were sensitive to differences in spread, participants overestimated the variability of the set by 50%. The results have implications for mechanisms underlying ensemble perception, which is the extraction of summary statistics from a set of objects. In particular, there are both shared and unique processes related to perceiving similarities across objects (such as the mean orientation) and perceiving differences (such as their spread). Both visual abilities were thorough and used the full set of lines, rather than using only a subset, but the perception of spread relied more heavily on differences presented at the beginning whereas perception of the mean relied more heavily on features of the lines at the end of the animation. The results also have implications for visualizations of uncertainty, such as hurricane forecasts. A perceptual bias to overestimate variability could help counteract cognitive biases to underestimate variability. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

What is best criterion for determining statistical significance? In psychology, the criterion has been p < .05. This criterion has been criticized since its inception, and the criticisms have been rejuvenated with recent failures to replicate studies published in top psychology journals. Several replacement criteria have been suggested including reducing the alpha level to .005 or switching to other types of criteria such as Bayes factors or effect sizes. Here, various decision criteria for statistical significance were evaluated using signal detection analysis on the outcomes of simulated data. The signal detection measure of area under the curve (AUC) is a measure of discriminability with a value of 1 indicating perfect discriminability and 0.5 indicating chance performance. Applied to criteria for statistical significance, it provides an estimate of the decision criterion’s performance in discriminating real effects from null effects. AUCs were high (M = .96, median = .97) for p values, suggesting merit in using p values to discriminate significant effects. AUCs can be used to assess methodological questions such as how much improvement will be gained with increased sample size, how much discriminability will be lost with questionable research practices, and whether it is better to run a single high-powered study or a study plus a replication at lower powers. AUCs were also used to compare performance across p values, Bayes factors, and effect size (Cohen’s d). AUCs were equivalent for p values and Bayes factors and were slightly higher for effect size. Signal detection analysis provides separate measures of discriminability and bias. With respect to bias, the specific thresholds that produced maximally-optimal utility depended on sample size, although this dependency was particularly notable for p values and less so for Bayes factors. The application of signal detection theory to the issue of statistical significance highlights the need to focus on both false alarms and misses, rather than false alarms alone.

Useful data visualizations have the potential to leverage the visual system's natural abilities to process and summarize simple and complex information. Here, we tested whether the design recommendations made for pairwise comparisons generalize to the detection of trends. We created two different types of graphs: line graphs and stripplots. These graphs were created from identical datasets that simulated temperature changes across time. These datasets varied in the type of trend (linear and exponential). Human observers performed a trend detection task for which they judged whether the trend in temperature over time was increasing or decreasing. Participants were more sensitive to trend direction with line graphs compared to stripplots. Participants also demonstrated a systematic bias to respond that the trend was increasing for line graphs. However, this bias decreased with increasing sensitivity. Despite the better sensitivity to line graphs, more than half of the participants found the stripplots more appealing and liked them more than the line graphs. In conclusion, our results indicate that, for trend detection, depicting data with position (line graphs) leads to better performance compared to depicting graphs with color (stripplots). Yet, graphs with color (stripplots) were preferred over the line graphs, suggesting that there may be a tradeoff between the aesthetic design of the graphs and the precision in communicating the information.

The action-specific account of spatial perception asserts that a perceiver's ability to perform an action, such as hitting a softball or walking up a hill, impacts the visual perception of the target object. Although much evidence is consistent with this claim, the evidence has been challenged as to whether perception is truly impacted, as opposed to the responses themselves. These challenges have recently been organized as six pitfalls that provide a framework with which to evaluate the empirical evidence. Four case studies of action-specific effects are offered as evidence that meets the framework's high bar, and thus that demonstrates genuine perceptual effects. That action influences spatial perception is evidence that perceptual and action-related processes are intricately and bidirectionally linked.

Visualizing data through graphs can be an effective way to communicate one’s results. A ubiquitous graph and common technique to communicate behavioral data is the bar graph. The bar graph was first invented in 1786 and little has changed in its format. Here, a replacement for the bar graph is proposed. The new format, called a hat graph, maintains some of the critical features of the bar graph such as its discrete elements, but eliminates redundancies that are problematic when the baseline is not at 0. Hat graphs also include elements designed to improve Gestalt grouping principles and engage object-based attention. The effectiveness of the hat graph was tested in two empirical studies for which participants had to find and identify the condition that lead to the biggest improvement from baseline to final test. Performance with hat graphs was 30 - 40% faster than with bar graphs.

According to the action-specific account of perception, a perceiver's ability to act influences how the environment is perceived. For example, in a computer-based task, participants perceive fish as moving faster when they use a smaller net, and are thus less effective at catching the fish (Witt & Sugovic, 2013a). Here, we examined the degree to which attention may influence perceptual judgments by requiring participants to engage in a secondary task that directed their attention either toward (Exp. 1) or away from (Exp. 2) the to-be-caught fish. Though perceived fish speed was influenced by participants' catching performance-replicating previous results-attentional allocation did not impact this relationship between catching performance and perceived fish speed. The present results suggest that action directly influences spatial perception, rather than exerting indirect effects via attentional processes.

The action-specific perception account holds that people perceive the environment in terms of their ability to act in it. In this view, for example, decreased ability to climb a hill because of fatigue makes the hill visually appear to be steeper. Though influential, this account has not been universally accepted, and in fact a heated controversy has emerged. The opposing view holds that action capability has little or no influence on perception. Heretofore, the debate has been quite polarized, with efforts largely being focused on supporting one view and dismantling the other. We argue here that polarized debate can impede scientific progress and that the search for similarities between 2 sides of a debate can sharpen the theoretical focus of both sides and illuminate important avenues for future research. In this article, we present a synthetic review of this debate, drawing from the literatures of both approaches, to clarify both the surprising similarities and the core differences between them. We critically evaluate existing evidence, discuss possible mechanisms of action-specific effects, and make recommendations for future research. A primary focus of future work will involve not only the development of methods that guard against action-specific postperceptual effects but also development of concrete, well-constrained underlying mechanisms. The criteria for what constitutes acceptable control of postperceptual effects and what constitutes an appropriately specific mechanism vary between approaches, and bridging this gap is a central challenge for future research.

A common conceptualization of signal detection theory (SDT) holds that if the effect of an experimental manipulation is truly perceptual, then it will necessarily be reflected in a change in d' rather than a change in the measure of response bias. Thus, if an experimental manipulation affects the measure of bias, but not d', then it is safe to conclude that the manipulation in question did not affect perception but instead affected the placement of the internal decision criterion. However, the opposite may be true: an effect on perception may affect measured bias while having no effect on d'. To illustrate this point, we expound how signal detection measures are calculated and show how all biases—including perceptual biases—can exert their effects on the criterion measure rather than on d'. While d' can provide evidence for a perceptual effect, an effect solely on the criterion measure can also arise from a perceptual effect. We further support this conclusion using simulations to demonstrate that the Müller-Lyer illusion, which is a classic visual illusion that creates a powerful perceptual effect on the apparent length of a line, influences the criterion measure without influencing d'. For discrimination experiments, SDT is effective at discriminating between sensitivity and bias but cannot by itself determine the underlying source of the bias, be it perceptual or response based.

Can one’s ability to perform an action, such as hitting a softball, influence one’s perception? According to the action-specific account, perception of spatial layout is influenced by the perceiver’s abilities to perform an intended action. Alternative accounts posit that purported effects are instead due to nonperceptual processes, such as response bias. Despite much confirmatory research on both sides of the debate, researchers who promote a response-bias account have never used the Pong task, which has yielded one of the most robust action-specific effects. Conversely, researchers who promote a perceptual account have rarely used the opposition’s preferred test for response bias, namely, the postexperiment survey. The current experiments rectified this. We found that even for people naive to the experiment’s hypothesis, the ability to block a moving ball affected the ball’s perceived speed. Moreover, when participants were explicitly told the hypothesis and instructed to resist the influence of their ability to block the ball, their ability still affected their perception of the ball’s speed.

The visual system is influenced by action. Objects that are easier to reach or catch look closer and slower, respectively. Here, we describe evidence for one action-specific effect, and show that none of the six pitfalls can account for the results. Vision is not an isolate module, as shown by this top-down effect of action on perception.

Distances on hills are judged as farther than when the same distance is presented on the flat ground. The hypothesized reason for this difference is because perception is influenced by the increased effort required to walk up a hill than to walk the same distance on flat ground. Alternatively, distances presented up a hill might be judged as farther for other, nonperceptual reasons such as bias from demand characteristics. To test whether distances on hills are perceived as farther or are merely judged as farther, we used a variety of measures, including visual matching and blindwalking tasks, and found similar effects across all measures. This convergence is consistent with a perceptual explanation. Second, we mined our data with the goal of making recommendations for future research on this paradigm. Although all of the perceptual measures used showed similar effects, visual matching was the only measure that had good intrasubject reliability. We recommend that future research on this action-specific effect could use any measure unless the research is geared towards individual differences, in which case, only the visual matching measure of perceived distance should be used.

Attention operates in the space near the hands with unique, action-related priorities. Here, we examined how attention treats objects on the hands themselves. We tested two hypotheses. First, attention may treat stimuli on the hands like stimuli near the hands, as though the surface of the hands were the proximal case of near-hand space. Alternatively, we proposed that the surface of the hands may be attentionally distinct from the surrounding space. Specifically, we predicted that attention should be slow to orient toward the hands in order to remain entrained to near-hand space, where the targets of actions are usually located. In four experiments, we observed delayed orienting of attention on the hands compared to orienting attention near or far from the hands. Similar delayed orienting was also found for tools connected to the body compared to tools disconnected from the body. These results support our second hypothesis: attention operates differently on the functional surfaces of the hand. We suggest this effect serves a functional role in the execution of manual actions.