Gut estimates: Pregnant women adapt to changing possibilities for squeezing through doorways

Risky actions: Why and how to estimate variability in motor performance

We describe the difficulties of measuring variability in performance, a critical but largely ignored problem in studies of risk perception. The problem seems intractable if a large number of successful and unsuccessful trials are infeasible. We offer a solution based on estimates of task-specific variability pooled across the sample. Using a dataset of adult performance in throwing and walking tasks, we show that mischaracterizing the slope leads to unacceptably large errors in estimates of performance levels that undermine analyses of risk perception. We introduce a "pooled-slope" solution that approximates estimates of individual variability in performance and outperforms arbitrary assumptions about performance variability within and across tasks. We discuss the advantages of objectively measuring performance based on the rate of successful attempts-modeled via psychometric functions-for improving comparisons of risk across participants, tasks, and studies.

Higher order affordances

Affordances are opportunities for action for a given animal (or animals) in a given environment or situation. The concept of affordance has been widely adopted in the behavioral sciences, but important questions remain. We propose a new way of understanding the nature of affordances; in particular, how affordances are related to one another. We claim that many - perhaps most - affordances emerge from non-additive relations among other affordances, such that some affordances are of higher order relative to other affordances. That is, we propose that affordances form a continuous category of perceiveables that differ only in whether and how they relate to other affordances. We argue that: (1) opportunities for behaviors of all kinds can be described as affordances, (2) some affordances emerge from relations between animal and environment, whereas most affordances emerge from relations between other affordances, and (3) all affordances lawfully structure ambient energy arrays and, therefore, can be perceived directly. Our concept of higher order affordances provides a general account of behavioral phenomena that traditionally have been interpreted in terms of cognitive processes (e.g., remembering or imagining) as well as behavioral phenomena that have traditionally been interpreted in terms of cultural rules, such as conventions, or customs.

Does how I feel change how I move? The influence of anxiety, self-efficacy and resilience on movement in adults with Developmental Coordination Disorder

BACKGROUND

Anxiety and movement consistency both influence movement in individuals with Developmental Coordination Disorder (DCD).

AIMS

This study investigated the influence of anxiety, self-efficacy, resilience and movement variability on perceptions and actions of adults with and without DCD.

METHODS

17 adults with DCD and 17 adults with typical motor skills (TMS) (age and sex-matched) completed a questionnaire and three experimental tasks: two perceptual judgement tasks (static and dynamic conditions), and an executed action task involving judging and walking through different-sized gaps between doors.

RESULTS

No significant relationships were detected between general or movement-specific anxiety, self-efficacy or resilience and perceptual judgement or movement behaviour; however, movement consistency did significantly relate to movement execution in both groups. Correlations showed adults with DCD with lower movement-specific self-efficacy left bigger safety margins, and indicated stronger links between perception and action in TMS adults. In the adults with DCD there was no significant correlation between the point of behaviour change (critical ratio) in the perceptual judgement and executed action tasks, suggesting a less smoothly linked perception-action cycle than in the TMS adults.

CONCLUSIONS AND IMPLICATIONS

Results highlight the importance of movement variability and motor control in the movement behaviour of adults with DCD, while illustrating the importance of studying perception and action together, especially when comparing populations, to elucidate how these may be constrained differently by individual-, task- and environmental-based constraints.

Representations of the relative proportions of body part width

Despite our wealth of experience with our bodies, our perceptions of our body size are far from veridical. For example, when estimating the relative proportions of their body part lengths, using the hand as a metric, individuals tend to exhibit systematic distortions which vary across body parts. Whilst extensive research with healthy populations has focused on perceptions of body part length, less is known about perceptions of the width of individual body parts and the various components comprising these representations. Across four experiments, representations of the relative proportions of body part width were investigated for both the self and other, and when using both the hand, or a hand-sized stick as the metric. Overall, we found distortions in the perceived width of body parts; however, different patterns of distortions were observed across all experiments. Moreover, the variability across experiments appears not to be moderated by the type of metric used or individuals' posture at the time of estimation. Consequently, findings suggest that, unlike perceptions of body part length, assessed using an identical methodology, our representations of the width of the body parts measured in this task are not fixed and vary across individuals and context. We propose that, as stored width representations of these parts are not necessarily required for navigating our environments, these may not be maintained by our perceptual systems, and thus variable task performance reflects the engagement of idiosyncratic guessing strategies.

The Relationship between Body Mass Index, Body Dissatisfaction and Mood Symptoms in Pregnant Women

Background: High body mass and adiposity during pregnancy can contribute to psychological distress, and body dissatisfaction may be a potential underlying mechanism of this association. Objective. This study aimed to evaluate the mediational role of body dissatisfaction in the relationship between body mass index (BMI) and depressive and anxious symptoms, respectively. Methods: Given the cross-sectional design of this study, two alternative models were investigated, positing that BMI was related to depressive (Model 1a) and anxious symptoms (Model 2a), which, in turn, predicted body dissatisfaction. Seventy-two pregnant women in the third trimester of pregnancy completed the Body Image Disturbance Questionnaire, the Beck Depression Inventory-II and the State-Trait Anxiety Inventory, as well as a demographic form assessing their BMI. Results: As hypothesized, body dissatisfaction mediated the relationship between BMI and psychopathological symptoms. Moreover, the alternative models of reverse mediation were also significant, suggesting that psychopathological symptoms mediated the relationship between BMI and body dissatisfaction. Findings from both the hypothesized and alternative models suggested that, on the one hand, higher distress symptoms associated with body dissatisfaction would result from high BMI and, on the other hand, that body dissatisfaction may result from the effect of BMI on distress symptoms. Conclusions: The present study suggests that body image theory and practice should be implemented by the inclusion of evidence-based clinical interventions for promoting psychological well-being during the antenatal period.

A systematic review of perception of affordances for the person-plus-object system

Human behavior often involves the use of an object held by or attached to the body, which modifies the individual's action capabilities. Moreover, most everyday behaviors consist of sets of behaviors that are nested over multiple spatial and temporal scales, which require perceiving and acting on nested affordances for the person-plus-object system. This systematic review investigates how individuals attune to information about affordances involving the person-plus-object system and how they (re)calibrate their actions to relevant information. We analyzed 71 articles-34 on attunement and 37 on (re)calibration with healthy participants-that experimentally investigated the processes involved in the perception of affordances for the person-plus-object system (including attunement, calibration, and recalibration). With respect to attunement, objects attached to the body create a multiplicity of affordances for the person-plus-object system, and individuals learned (1) to detect information about affordances of (and for) the person-plus-object system in a task and (2) to choose whether, when, and how to exploit those affordances to perform that task. Concerning (re)calibration, individuals were able (1) to quickly scale their actions in relation to the (changed) action capabilities of the person-plus-object system and (2) to perceive multiple functionally equivalent ways to exploit the affordances of that system, and these abilities improved with practice. Perceiving affordances for the person-plus-object system involves learning to detect the information about such affordances (attunement) and the scaling of behaviors to such information (calibration). These processes imply a general ability to incorporate an object attached to the body into an integrated person-plus-object system.

Performance variability and affordance perception: practice effects on perceptual judgments for walking versus throwing

To judge whether an action is possible, people must perceive "affordances"-the fit between features of the environment and aspects of their own bodies and motor skills that make the action possible or not. But for some actions, performance is inherently variable. That is, people cannot consistently perform the same action under the same environmental conditions with the same level of success. Decades of research show that practice performing an action improves perception of affordances. However, prior work did not address whether practice with more versus less variable actions is equally effective at improving perceptual judgments. Thirty adults judged affordances for walking versus throwing a beanbag through narrow doorways before and after 75 practice trials walking and throwing beanbags through doorways of different widths. We fit a "success" function through each participant's practice data in each task and calculated performance variability as the slope of the function. Performance for throwing was uniformly more variable than for walking. Accordingly, absolute judgment error was larger for throwing than walking at both pretest and posttest. However, absolute error reduced proportionally in both tasks with practice, suggesting that practice improves perceptual judgments equally well for more and less variable actions. Moreover, individual differences in variability in performance were unrelated to absolute, constant, and variable error in perceptual judgments. Overall, results indicate that practice is beneficial for calibrating perceptual judgments, even when practice provides mixed feedback about success under the same environmental conditions.

Training for walking through an opening improves collision avoidance behavior in subacute patients with stroke: a randomized controlled trial

PURPOSE

Paretic side collisions frequently occur in stroke patients, especially while walking through narrow spaces. We determined whether training for walking through an opening (T-WTO) while entering from the paretic side would improve collision avoidance behavior and prevent falls after 6 months.

MATERIALS AND METHODS

Thirty-eight adults with moderate-to-mild hemiparetic gait after stroke who were hospitalized in a rehabilitation setting were randomly allocated to the T-WTO (n = 20) or regular rehabilitation (R-Control; n = 18) program. Both groups received five sessions of 40 min per week, for three weeks total. T-WTO included walking through openings of various widths while rotating with the paretic side in front, and R-Control involved normal walking without body rotation. Obstacle avoidance ability, 10-m walking test, timed Up and Go test, Berg Balance Scale, Activities-specific Balance Confidence, the perceptual judgment of passability, and fall incidence were assessed.

RESULTS

Collision rate and time to passage of the opening in obstacle avoidance task significantly improved in the T-WTO group compared with those in the R-Control group. Contrast, T-WTO did not lead to significant improvements in other outcomes.

CONCLUSIONS

T-WTO improved efficiency and safety in managing subacute stroke patients. Such training could improve patient outcomes/safety because of the paretic body side during walking.

CLINICAL TRIAL REGISTRATION NO.

R000038375 UMIN000033926.

Can I Squeeze Through? Effects of Self-Avatars and Calibration in a Person-Plus-Virtual-Object System on Perceived Lateral Passability in VR

With the popularity of Virtual Reality (VR) on the rise, creators from a variety of fields are building increasingly complex experiences that allow users to express themselves more naturally. Self-avatars and object interaction in virtual worlds are at the heart of these experiences. However, these give rise to several perception based challenges that have been the focus of research in recent years. One area that garners most interest is understanding the effects of self-avatars and object interaction on action capabilities or affordances in VR. Affordances have been shown to be influenced by the anthropometric and anthropomorphic properties of the self-avatar embodied. However, self-avatars cannot fully represent real world interaction and fail to provide information about the dynamic properties of surfaces in the environment. For example, pressing against a board to feel its rigidity. This lack of accurate dynamic information can be further amplified when interacting with virtual handheld objects as the weight and inertial feedback associated with them is often mismatched. To investigate this phenomenon, we looked at how the absence of dynamic surface properties affect lateral passability judgments when carrying virtual handheld objects in the presence or absence of gender matched body-scaled self-avatars. Results suggest that participants can calibrate to the missing dynamic information in the presence of self-avatars to make lateral passability judgments, but rely on their internal body schema of a compressed physical body depth in the absence of self-avatars.

Perceptual-motor recalibration is intact in older adults

From an ecological perspective, perceptual-motor recalibration should be a robust and adaptable process, but there are suggestions that older adults may recalibrate slower. Therefore, this study investigated the age-related temporal effects in perceptual-motor recalibration after motor disturbances. In three experiments, we disturbed young and older adults' perception-action by fitting weights around their ankles and asking them to climb stairs or cross obstacles repeatedly. In Experiment 1, participants (n = 26) climbed stairs with different ankle weights. An innovative methodology was applied, identifying the timeline of recalibration as the point where a stable movement pattern emerged. Experiment 1 showed that older adults recalibrated slower than young adults in lighter (but not heavier) weight conditions. In Experiment 2, participants (n = 24) crossed obstacles with different ankle weights. Results showed that older adults recalibrated faster than young adults. Finally, in Experiment 3, participants (n = 24) crossed obstacles of unpredictable and varying heights with heavy ankle weights. Again, results showed that older adults recalibrated faster than young adults. Taken together these results show that although older adults had reduced muscle strength and flexibility, they recalibrated quickly, especially when the task was more challenging.

Respiratory rhythm affects recalibration of body ownership

Change in body perception requires recalibration of various sensory inputs. However, it is less known how information other than sensations relates to the recalibration of body perception. Here, we focused on the relationship between respiration and cognition and investigated whether respiratory rhythms are related to the recalibration of hand perception. We built a visual feedback environment, in which a mannequin hand moved in conjunction with its own respiratory rhythm, and participants performed an experiment under conditions in congruency/incongruency for spatial and temporal factors. The temporal and spatial congruency between own respiratory rhythm and the mannequin hand markedly facilitated the phenomenon of hand ownership sense transfer to the mannequin hand, while incongruency had little effect on the change in hand ownership. The finding suggests that an internal model in the brain allows respiratory rhythms to be involved in the adaptation of the body's neural representations.

Did I Hit the Door? Effects of Self-Avatars and Calibration in a Person-Plus-Virtual-Object System on Perceived Frontal Passability in VR

The availability of new and improved display, tracking and input devices for Virtual Reality experiences has facilitated the use of partial and full body self-avatars in interaction with virtual objects in the environment. However, scaling the avatar to match the user's body dimensions remains to be a cumbersome process. Moreover, the effect of body-scaled self-avatars on size perception of virtual handheld objects and related action capabilities has been relatively unexplored. To this end, we present an empirical evaluation investigating the effect of the presence or absence of body-scaled self-avatars and visuo-motor calibration on frontal passability affordance judgments when interacting with virtual handheld objects. The self-avatar's dimensions were scaled to match the participant's eyeheight, arms length, shoulder width and body depth along the mid section. The results indicate that the presence of body-scaled self-avatars produce more realistic judgments of passability and aid the calibration process when interacting with virtual objects. Also, participants rely on the visual size of virtual objects to make judgments even though the kinesthetic and proprioceptive feedback of the object is missing or mismatched.

The Embodiment of Architectural Experience: A Methodological Perspective on Neuro-Architecture

People spend a large portion of their time inside built environments. Research in neuro-architecture-the neural basis of human perception of and interaction with the surrounding architecture-promises to advance our understanding of the cognitive processes underlying this common human experience and also to inspire evidence-based architectural design principles. This article examines the current state of the field and offers a path for moving closer to fulfilling this promise. The paper is structured in three sections, beginning with an introduction to neuro-architecture, outlining its main objectives and giving an overview of experimental research in the field. Afterward, two methodological limitations attending current brain-imaging architectural research are discussed: the first concerns the limited focus of the research, which is often restricted to the aesthetic dimension of architectural experience; the second concerns practical limitations imposed by the typical experimental tools and methods, which often require participants to remain stationary and prevent naturalistic interaction with architectural surroundings. Next, we propose that the theoretical basis of ecological psychology provides a framework for addressing these limitations and motivates emphasizing the role of embodied exploration in architectural experience, which encompasses but is not limited to aesthetic contemplation. In this section, some basic concepts within ecological psychology and their convergences with architecture are described. Lastly, we introduce Mobile Brain/Body Imaging (MoBI) as one emerging brain imaging approach with the potential to improve the ecological validity of neuro-architecture research. Accordingly, we suggest that combining theoretical and conceptual resources from ecological psychology with state-of-the-art neuroscience methods (Mobile Brain/Body Imaging) is a promising way to bring neuro-architecture closer to accomplishing its scientific and practical goals.

Perception of Affordances in Soccer: Kicking for Power Versus Kicking for Precision

Purpose: We investigated youth soccer players' perception of affordances for different types of kicks. Method: In the Power task, players judged the maximum distance they could kick the ball. In the Precision task, players judged how close to a designated target line they could kick the ball. Following judgments, players performed each task. Both judgments and performance were assessed immediately before and immediately after players competed in a regulation soccer match, thereby permitting us to assess possible effects of long-term experience on perceptual sensitivity to short-term changes in ability. We compared players from two league groups: U16 (mean age = 15.45 years, SD = 0.52 years) versus U18 (mean age = 17.55 years, SD = 0.52 years). Results: As expected, for the Power task actual kicking ability was greater for the U18 group (p < .05). In statistically significant interactions, we found that judgments of Power kicking ability differed before versus after match play, but only for the U16 group. We found no statistically significant effects for the Precision task. Conclusions: We identified interactions between long-term and short-term soccer experience which revealed that the effects of long-term experience on affordance perception were not general. Two additional years of playing experience (in the U18 group, relative to the U16 group) did not lead to an overall improvement in the perception of kicking-related affordances. Rather, variation in long-term experience was associated with changes in affordance perception which were situation-specific, being manifested only after playing a soccer match, and not before.

Perception of Affordances for Vertical and Horizontal Jumping in Children: Gymnasts Versus Non-Athletes

Purpose: We investigated the perception of affordances for vertical jumping-and-reaching and horizontal jumping by children. Method: In the horizontal task, children were asked to judge their ability in the standing long jump. In the vertical task, children were asked to judge the height of a ball that they could run to, jump up, and reach with their fingertips. Following judgments, children performed both types of jumps. We compared gymnasts (children with at least 2 years of gymnastics training; 7.92 ± 0.91 years) versus children with no competitive athletic experience (7.74 ± 0.86 years). Results: As expected, actual ability was greater in gymnasts than in non-athletes, for both types of jump (each p < .001). We separately analyzed Constant Error and Absolute Error of judgments (relative to actual performance). Results revealed that gymnasts tended toward underestimation, while non-athletes tended toward overestimation. Absolute error differed between tasks for the non-athletes (p < .001), but for the gymnasts the difference between conditions was not significant (p = .25). Absolute error differed between groups for vertical jump-and-reach (p < .01) but not for horizonal jump (p = .17). Conclusions: Gymnastics experience was associated with a generalized tendency for children to underestimate their jumping ability. In addition, gymnastics experience was associated with judgment accuracy that was consistent across tasks. The results reveal that gymnastics training is associated with changes in athletic ability, but also with changes in the perception of affordances.

How far can I reach? The perception of upper body action capabilities in Parkinson's disease

Successful interaction within the environment is contingent upon one’s ability to accurately perceive the extent over which they can successfully perform actions, known as action boundaries. Healthy young adults are accurate in estimating their action boundaries and can flexibly update them to accommodate stable changes in their action capabilities. However, there are conditions in which motor abilities are subject to variability over time such as in Parkinson’s disease (PD). PD impairs the ability to perform actions and can lead to variability in perceptual-motor experience, but the effect on the perceptions of their action boundaries remains unknown. This study investigated the influence of altered perceptual-motor experience during PD, on the perceptions of action boundaries for reaching, grasping, and aperture passing. Thirty participants with mild-to-moderate idiopathic PD and 26 healthy older adults provided estimates of their reaching, grasping, and aperture-passing ability. Participants’ estimates were compared with their actual capabilities. There was no evidence that individuals with PD’s perceptions were less accurate than those of healthy controls. Furthermore, there was some evidence for more conservative estimates than seen in young healthy adults in reaching (both groups) and aperture passing (PD group). This suggests that the ability to judge action capabilities is preserved in mild to moderate PD.

Perceiving action boundaries for overhead reaching in a height-related situation

To successfully interact within our environment, individuals need to learn the maximum extent (or minimum) over which they can perform actions, popularly referred to as action boundaries. Because people learn such boundaries over time from perceptual motor feedback across different contexts, both environmental and physiological, the information upon which action boundaries are based must inherently be characterised by variability. With respect to reaching, recent work suggests that regardless of the type of variability present in their perceptual-motor experience, individuals favoured a liberal action boundary for horizontal reaching. However, the ways in which action boundaries are determined following perceptual-motor variability could also vary depending on the environmental context as well as the type of reach employed. The present research aimed to established whether the perceptual system utilises the same strategy for all types of reaches over different contexts. Participants estimated their overhead reachability following experience reaching with either a long or a short virtual arm, or a virtual arm that varied in length - while standing on the edge of a rooftop or standing on the ground. Results indicated that while similar strategies were used to determine action boundaries in both height- and non-height-related context, participants were significantly more conservative with their reachability estimates in the height-related context. Participants were sensitive to the probabilistic information associated with different arm's reach they have experienced during the calibration phase, and used a weighted average of reaching experience to determine their action boundary under conditions of uncertainty.

It's in your hands: How variable perception affects grasping estimates in virtual reality

Successful interaction within one’s environment is contingent upon one’s ability to accurately perceive the extent over which actions can be performed, referred to as action boundaries. As our possibilities for action are subject to variability, it is necessary for individuals to be able to update their perceived action boundaries to accommodate for variance. While research has shown that individuals can update their action boundaries to accommodate for variability, it is unclear how the perceptual system calibrates to this variance to inform our action boundaries. This study investigated the influence of perceptual motor variability by analysing the effect of random and systematic variability on perceived grasp ability in virtual reality. Participants estimated grasp ability following perceptual-motor experience with a constricted, normal, extended, or variable grasp. In Experiment 1, participants experienced all three grasping abilities (constricted, normal, extended) 33% of the time. In Experiment 2 participants experienced the constricted and normal grasps 25% of the time, and the extended grasp 50% of the time. The results indicated that when perceptual-motor feedback is inconsistent, the perceptual system disregards the frequency of perceptual-motor experience with the different action capabilities and considers each action capability experienced as a type, and subsequently calibrates to the average action boundary experienced by type.

Can Dogs Limbo? Dogs' Perception of Affordances for Negotiating an Opening

Simple Summary

Recent behavioral research with domestic dogs has focused largely on their social cognition: how they interact with and interpret both other dogs and humans. Less well studied are the various aspects of their perceptual experience which might provide knowledge of how they understand the non-social world and themselves. In two studies, we look at how dogs navigate their environment. We first set up a situation to test whether dogs understand when they are too big to go through an opening; we also look at how they adjust their bodies to increasingly smaller (shorter) openings. We then also look at how dogs navigate an opening when their body width is effectively increased by their holding a stick in their mouth. We find that dogs show more hesitation approaching openings that are too small than ones through which they comfortably fit. Dogs of all sizes also change their behavior in a uniform way to negotiate short openings. When holding a stick, dogs did not initially change their behavior but are able to negotiate through an opening with experience. Researching how dogs navigate through a changing environment may be a fruitful way to begin to understand their sense of themselves.

Abstract

Very little research has focused on canines’ understanding of their own size, and their ability to apply this understanding to their surroundings. The current study tests domestic dogs’ judgment of their body size in relation to a changing environment in two novel experimental situations: when encountering an opening of decreasing height (Study 1) and when negotiating an opening when carrying a stick in their mouth (Study 2). We hypothesized that if dogs understand their own body size, they will accurately judge when an opening is too small for their body to fit through, showing longer latencies to approach the smaller openings and adjusting their body appropriately to get through—although this judgment may not extend to when their body size is effectively increased. In line with these hypotheses, we found that the latency for subjects to reach an aperture they could easily fit through was significantly shorter than to one which was almost too small to fit through. We also found that the order of subjects’ adjustments to negotiate an aperture was invariant across individuals, indicating that dogs’ perception of affordances to fit through an aperture is action-scaled. Preliminary results suggest that dogs’ approach behavior is different when a horizontal appendage is introduced, but that dogs were able to alter their behavior with experience. These results are consistent with the hypothesis that dogs understand their own body size and the affordances of their changing environment.

Predicting aperture crossing behavior from within-trial metrics of motor control reliability

Actors utilize intrinsically scaled information about their geometric and dynamic properties when perceiving their ability to pass through openings. Research about dynamic factors of affordance perception have shown that the reliability of a given movement, or the precision of one's motor control for that movement, increase the buffer space used when interacting with the environment. While previous work has assessed motor control reliability as a person-level variable (i.e., behavior is aggregated across many trials), the current study assessed how characteristics of motor control and movement reliability within a single trial impact real-time action strategies for passing through apertures. Participants walked 5 m and then passed through apertures of various widths while their motions were tracked. For each trial, we collected walking time-series data, then calculated the magnitude and complexity of the lateral sway. Assessing two behavioral measures of the buffer, we found that trial-level metrics of motor control reliability, in addition to the person-level metrics previously studied, significantly predicted the buffer on each trial. This study supports previous claims that actors pick up real-time information about their dynamic capabilities in order to perceive and act within their environment. Further, the study recommends that future affordance research consider trial-level movement data, including nonlinear analyses that inform the pattern and structure of motor control reliability.

Calibration of perception fails to transfer between functionally similar affordances

Prior work shows that the calibration of perception and action transfers between actions depending on their functional similarity: Practising (and thus calibrating perception of) one affordance will also calibrate perception for an affordance with a similar function but not for an affordance with a disparate function. We tested this hypothesis by measuring whether calibration transferred between two affordances for passing through openings: squeezing sideways through doorways without becoming stuck and fitting sideways through doorways while avoiding collision. Participants wore a backpack to alter affordances for passage and create a need for perceptual recalibration. Calibration failed to transfer between the two actions (e.g., practising squeezing through doorways calibrated perception of squeezing but not fitting). Differences between squeezing and fitting affordances that might have required different information for perception and recalibration are explored to understand why calibration did not transfer. In light of these results, we propose a revised hypothesis-calibration transfers between affordances on the basis of both functional and informational similarity.

Adolescent Awkwardness: Alterations in Temporal Control Characteristics of Posture with Maturation and the Relation to Movement Exploration

A phenomenon called adolescent awkwardness is believed to alter motor control, but underlying mechanisms remain largely unclear. Since adolescents undergo neurological and anthropometrical changes during this developmental phase, we hypothesized that adolescents control their movements less tightly and use a different coordinative structure compared to adults. Moreover, we tested if emerging differences were driven by body height alterations between age groups. Using 39 reflective markers, postural movements during tandem stance with eyes open and eyes closed of 12 adolescents (height 168.1 ± 8.8 cm) and 14 adults were measured, in which 9 adults were smaller or equal than 180 cm (177.9 ± 3.0 cm) and 5 taller or equal than 190 cm (192.0 ± 2.5 cm). A principal component analysis (PCA) was used to extract the first nine principal movement components (PMk). The contribution of each PMk to the overall balancing movement was determined according to their relative variance share (rVARk) and tightness of motor control was examined using the number of times that the acceleration of each PMk changed direction (Nk). Results in rVARk did not show significant differences in coordinative structure between adolescents and adults, but Nk revealed that adolescents seem to control their movements less tightly in higher-order PMk, arguably due to slower processing times and missing automatization of postural control or potential increases in exploration. Body height was found to not cause motor control differences between age groups.

To step or to spring: the influence of state anxiety on perceptual judgements and executed action

Emotional state, in particular anxiety, has been shown to constrain perceptual judgement of action capabilities. However, whether anxiety also constrains actual behaviour is unknown. The current study, therefore, aimed to determine whether state anxiety constrained firstly perceptual judgements of action capabilities and secondly actual behaviour. To do this, we asked participants to make perceptual judgements and perform action behaviours in relation to crossing ground-based apertures representing puddles. State anxiety was measured in 30 participants using the State-Trait Anxiety Inventory. The critical ratio of aperture size relative to leg length at which participants' behaviour choice would switch between a step and a spring was calculated. In a perceptual judgement task, participants judged the ratio at which they would choose to switch. In a subsequent executed action task, the ratio at which they actually switched was measured. Perceptual critical ratio could be predicted via state anxiety and age, while action critical ratio was not predicted by either. Therefore, this study has demonstrated that state anxiety and age both constrain perceptual judgement of action capabilities, as shown in previous studies. However, this does not seem to result in a change in emergent behaviour. This highlights the importance of measuring emergent behaviour rather than inferring it from perceptual judgements even when they are couched in terms of action.

When weight is an encumbrance; avoidance of stairs by different demographic groups

BACKGROUND

Locomotion is an energy costly behaviour, particularly when it entails raising weight against gravity. Minimization of locomotor costs appears a universal default. Avoidance of stair climbing helps humans minimise their energetic costs. In public access settings, demographic subgroups that raise more 'dead' weight than their comparison groups when climbing are more likely to avoid stairs by choosing the escalator. Individuals who minimise stair costs at work, however, can accumulate a deficit in energy expenditure in daily life with potential implications for weight gain. This paper tests the generality of avoidance of stairs in pedestrians encumbered by additional weight in three studies.

METHODS

Pedestrian choices for stairs or the alternative were audited by trained observers who coded weight status, presence of large bags and sex for each pedestrian. Sex-specific silhouettes for BMIs of 25 facilitated coding of weight status. Choices between stairs and a lift to ascend and descend were coded in seven buildings (n = 26,981) and at an outdoor city centre site with the same alternatives (n = 7,433). A further study audited choices to ascend when the alternative to stairs was a sloped ramp in two locations (n = 16,297). Analyses employed bootstrapped logistic regression (1000 samples).

RESULTS

At work and the city centre site, the overweight, those carrying a large bag and females avoided both stair climbing and descent more frequently than their comparison groups. The final study revealed greater avoidance of stairs in these demographic subgroups when the alternative means of ascent was a sloped ramp.

DISCUSSION

Minimization of the physiological costs of transport-related walking biases behaviour towards avoidance of stair usage when an alternative is available. Weight carried is an encumbrance that can deter stair usage during daily life. This minimization of physical activity costs runs counter to public health initiatives to increase activity to improve population health.

The Representation of Body Size: Variations With Viewpoint and Sex

Perceived body size is a fundamental construct that reflects our knowledge of self and is important for all aspects of perception, yet how we perceive our bodies and how the body is represented in the brain is not yet fully understood. In order to understand how the brain perceives and represents the body, we need an objective method that is not vulnerable to affective or cognitive influences. Here, we achieve this by assessing the accuracy of full-body size perception using a novel psychophysical method that taps into the implicit body representation for determining perceived size. Participants were tested with life-size images of their body as seen from different viewpoints with the expectation that greater distortions would occur for unfamiliar views. The Body Shape Questionnaire was also administered. Using a two-alternative forced choice design, participants were sequentially shown two life-size images of their whole body dressed in a standardized tight-fitting outfit seen from the front, side, or back. In one image, the aspect ratio (with the horizontal or vertical dimension fixed) was varied using an adaptive staircase, while the other was undistorted. Participants reported which image most closely matched their own body size. The staircase honed in on the distorted image that was equally likely as the undistorted photo to be judged as matching their perception of themselves. From this, the perceived size of their internal body representation could be calculated. Underestimation of body width was found when the body was viewed from the front or back in both sexes. However, females, but not males, overestimated their width when the body was viewed from the side. Height was perceived accurately in all views. These findings reveal distortions in perceived size for healthy populations and show that both viewpoint and sex matter for the implicit body representation. Though the back view of one’s body is rarely–if ever–seen, perceptual distortions were the same as for the front view. This provides insight into how the brain might construct its representation of three-dimensional body shape.

Does it still fit? - Adapting affordance judgments to altered body properties in young and older adults

Actor-related affordance judgments are decisions about potential actions that arise from environmental as well as bodily and cognitive conditions. The system can be challenged by sudden changes to otherwise rather stable actor references e.g. due to accidental bodily injuries or due to brain damage and resulting motor and cognitive constraints. The current study investigated adaptation to suddenly artificially altered body properties and its reversibility in healthy young versus older adults. Participants were asked to judge whether they would be able to fit their hand through a given horizontal opening (Aperture Task). Body alterations were induced by equipping participants with one hand splint for 24 hours that enlarged the hand in width and height. Participants were tested before and directly after putting the splint on as well as after a habituation period of 24 hours. To assess reversibility, participants were tested again directly after removing the splint and one day later. Judgment accuracy values and detection theory measures were reported. Both, young and older adults judged more conservatively when body properties were altered compared to initial judgments for normal body properties. Especially older adults showed major difficulties in such quick adaptation. Older adults' judgment accuracy as well as perceptual sensitivity were significantly lowered when body properties were suddenly altered. Importantly, lowered judgment performance occurred for both, the splinted as well as the non-splinted hand in older adults. Only after 24 hours of habituation, older adults tended to regain initial performance levels showing adaptive behavior to the altered condition. Removing the hand splint for one day was sufficient to reverse these adaptive effects. Our study results suggest that aging slows down adaptation to sudden bodily alterations affecting actor-related affordance judgments. We propose that these altered processes may go along with uncertainty and a heightened concern about potential consequences of misjudgments. Clearly, future studies are needed to further elucidate the underlying processes of adaptation in affordance judgments. These may reveal major implications for the aging society and its associated problems with an increased risk of falling or stroke related bodily constraints.

The Ability of Adults of Different Size to Egress Through Confined Space Apertures

OBJECTIVE

To determine minimum egress apertures in healthy adults of different body size.

BACKGROUND

Body space requirements have traditionally been considered from an industrial perspective, facilitating safe confined-space working. However, increased typical body size resulting from global obesity renders traditional assumptions of body size inappropriate. This has potentially far-reaching consequences for evacuation planning, due to diminished clearance space, slower movement, and increased chance of physical entrapment. Critically, no current literature describes the minimum apertures adults can negotiate.

METHOD

Forty-eight men and 40 women underwent anthropometric and 3-D scanning assessments from which anatomical dimensions were extracted. Additionally, a wall egress task was undertaken through an aperture that was progressively narrowed until individuals failed to pass. Minimum egress aperture was predicted from anatomical variables using backwards elimination regression.

RESULTS

Minimum wall egress was best predicted from mass, abdominal depth, bideltoid breadth and chest depth. Passes and fails, discriminated using binary logistic regression, identified chest depth and abdominal depth as influential for wall egress success at selected apertures, with a gender interaction manifest at abdominal depth.

CONCLUSION

Minimum egress aperture relates to body size and can be predicted from anatomical variables; however, men and women display subtle differences in egress capability.

APPLICATION

In public and industrial settings, egress capability in restricted spaces is affected by size and gender, with profound implications for safety, which relate to increased typical body size associated with global obesity.

Development of affordance perception and recalibration in children and adults

Changes in the body over developmental time (e.g., physical growth) as well as over shorter timescales (e.g., wearing a backpack, carrying a large object) alter possibilities for motor action. How well can children recalibrate their perception of action possibilities to account for sudden changes to body size? The current study compared younger children (4-7 years), older children (8-11 years), and adults as they decided whether they could squeeze through doorways of varying widths. To test for age-related changes in recalibration to modified abilities versus perception of unmodified abilities, half of the participants wore a backpack while making judgments and squeezing through doorways and half did not. Results indicated that judgment accuracy improved with age but that participants had more difficulty when recalibrating to modified abilities. Bias in decision making also changed with age; whereas younger children made riskier decisions by attempting to fit through impossibly small doorways, older children were more cautious. Some particularly cautious participants never generated practice feedback by attempting (and failing) to fit through smaller doorways, which prevented them from recalibrating. Taken together with previous literature, the results of the current study suggest that the development of perception for unmodified versus modified ability proceeds at different rates and depends on the particular motor task.

Effectiveness of adults' spontaneous exploration while perceiving affordances for squeezing through doorways

When motor abilities change, people need to generate information to recalibrate their perception through active exploration. Most prior research has focused on observers' ability to update perception by executing experimenter-specified exploratory behaviors, however, the question of how observers spontaneously choose how to explore has been overlooked. We asked how effectively adults decide to explore when adapting to changes in their ability to squeeze through doorways. Results revealed that participants made efficient decisions about when to explore by approaching and practicing-they most often explored doorways that were near the limit of their abilities, and participants explored less often as their perceptual calibration improved. However, participants made sub-optimal decisions about how to explore, which resulted in a failure to fully recalibrate. We discuss the implications of these findings for understanding the processes of perceptual-motor recalibration that underlie real-world behavior.

Perceiving affordances in sports through a momentum lens

In this experimental study, we tested whether athletes' judgments of affordances and of environmental features vary with psychological momentum (PM). We recruited golf, hockey, and tennis players, who were assigned to a positive or negative momentum condition. We designed a golf course on which participants made practice putts, after which they were asked to place the ball at their maximum "puttable" distance and to judge the hole size. Next, participants played a golf match against an opponent, in which the first to take a lead of 5 points would win the match. Participants were told that they could win a point by making the putt or by being closest to the hole. They wore visual occlusion goggles to prevent them from seeing the actual result, and the experimenter manipulated the scoring pattern to induce positive or negative PM. Participants in the positive momentum condition came back from a four-point lag to a four-point lead, whereas those in the negative momentum condition underwent the opposite scenario. We then asked the participants again to indicate their maximum puttable distance from the hole and to judge the hole size. After the manipulation, participants judged the maximum puttable distance to be longer in the positive momentum condition and shorter in the negative momentum condition. For the hole-size judgments, there were no significant effects. These results provide first indications for the idea that athletes' affordances change when they experience positive PM compared to negative PM. This sheds a new light on the dynamics of perception-action processes and PM in sports.

Visual detection of affordances for aperture negotiation in people with Parkinson disease

BACKGROUND

An essential requirement for the guidance of action in cluttered environments is that people can accurately perceive what actions are afforded by particular surroundings given the person's action capabilities. Research has shown that healthy young individuals turn their shoulders when walking through a doorway when the aperture is less than a certain percentage of their shoulder width and that they are able to detect this critical width with visual inspection. These findings imply that movements are constrained by perception of the environment in body-scaled unit.

OBJECTIVES

The present work examined whether the visual affordance of doorway passability is altered in people with Parkinson disease (PD).

METHODS

People with PD, healthy age-matched controls, and young adults (16 participants per group) walked through a series of apertures scaled to shoulder width. Participants also had to visually judge a series of apertures to determine if they could walk through the gap with their normal gait pattern. Finally, participants had to estimate their eye height.

RESULTS

Statistical analysis revealed that people with PD initiated shoulder turning to go through the doorway at larger apertures (A) relative to their shoulder (S) width (A/S = 1.61) in comparison to healthy age-matched participants (A/S = 1.41) and young adults (A/S = 1.26). In comparison to healthy participants, People with PD also judged wider apertures as impassable. Individuals with PD were less accurate in their estimation of eye height (Error = 10.1%) than the healthy older (Error = 6.29%) and younger adults (Error = 4.79%).

CONCLUSIONS

PD significantly impacted the affordances for aperture negotiation. Such altered perceptual affordances may contribute to gait pattern changes in people with PD when walking through doorways. These findings suggest that some of the motor symptoms in PD might have a perceptual underpinning.

Getting a grasp on action-specific scaling: A response to Witt (2017)

Can higher level cognition directly influence visual spatial perception? Many recent studies have claimed so, on the basis that manipulating cognitive factors (e.g., morality, emotion, action capacity) seems to directly affect perception. However, Firestone and Scholl (Behavioral and Brain Sciences, 39, 1–77, 2016) argued that such studies often fall prey to at least one of six pitfalls. They further argued that if an effect could be accounted for by any of these pitfalls, it is not a true demonstration of a top-down influence of cognition on perception. In response to Firestone and Scholl (Behavioral and Brain Sciences, 39, 1–77, 2016), Witt (Psychonomic Bulletin & Review, 24(4), 999–1021, 2017) discussed four action-specific scaling effects which, she argued, withstand all six pitfalls and thus demonstrate true perceptual changes caused by differences in action capacity. Her third case study was the influence of apparent grasping capacity on perceived object size. In this article, we provide new interpretations of previous findings and assess recent data which suggest that this effect is not, in fact, perceptual. Instead, we believe that many earlier studies showing this effect are subject to one or more of the pitfalls outlined by Firestone and Scholl (Behavioral and Brain Sciences, 39, 1–77, 2016). We substantiate our claims with recent empirical evidence from our laboratory which suggests that neither actual nor perceived grasping capacity directly influence perceived object size. We conclude that studies manipulating grasping capacity do not provide evidence for the action-specific account because variation in this factor does not directly influence size perception.

Perception of Affordances for Stepping Over an Expanse With Crutches

Perception of possibilities for behavior reflects the task-specific fit between action capabilities and environmental properties. We investigated whether this is so for a behavior that requires spontaneously and temporarily coordinating anatomical components and inert objects into a person-plus-object action system-stepping over an expanse with crutches. We found that perception of this affordance (a) scaled to an anthropometric property of primary relevance to performing this behavior (leg length), (b) reflected the ability to perform this behavior, and that (c) variability in perception decreased with practice perceiving this affordance. The results are consistent with the proposal that perceiving affordances for a given behavior requires assembling a task-specific perceptual instrument.

Physical Growth, Body Scale, and Perceptual-Motor Development

In this chapter we consider from the theoretical framework of the ecological approach to perception and action, the relations between physical growth and body scale in the context of children's perceptual-motor development. Body scale and the timescale of its change through growth are shown to relate to the emergence and dissolution of the fundamental skills in infancy, the perception of what an environment affords functionally for action, together with the emergent pattern of movement coordination. A central issue in typical and atypical motor development is the mapping of the timescale of adaptive change in the acquisition of perceptual-motor skill to the accompanying timescale of change in physical growth.

Rate of recalibration to changing affordances for squeezing through doorways reveals the role of feedback

Recalibration of affordance perception in response to changing motor abilities can only occur if observers detect appropriate perceptual information. Recent work suggests that although many affordances can be recalibrated without practicing the specific action to gather outcome feedback-information about whether the attempted action succeeded or failed-calibration of other affordances might depend on outcome feedback (Franchak, Attent Percept Psychophys 79:1816-1829, 2017). However, past work could not rule out the possibility that practicing the action produced perceptual-motor feedback besides outcome feedback that facilitated recalibration. The results of two experiments support the hypothesis that recalibration in a doorway squeezing task depends on outcome feedback as opposed to perceptual-motor feedback. After putting on a backpack that changed participants' doorway squeezing ability, affordance judgments were uncalibrated and remained so even after making repeated judgments. However, after practicing the action, which produced outcome feedback, judgments rapidly calibrated. Moreover, the order of feedback information directly impacted participants' judgments: Participants did not recalibrate if they received only success experience or only failure experience. Recalibration only occurred after participants received both types of feedback experiences, suggesting that outcome feedback is necessary for recalibration in the doorway squeezing task. More generally, the results of the current study support a key tenet of ecological psychology-that affordance perception depends on action-specific information about body-environment relations.

Exploratory behaviors and recalibration: What processes are shared between functionally similar affordances?

Recalibration of affordance perception allows observers to adapt to changes in the body's size or abilities that alter possibilities for action. Of key interest is understanding how exploratory behaviors lead to successful recalibration. The present study was designed to test a novel hypothesis-that the same processes of exploration and recalibration should generalize between affordances that share a similar function. Most affordances for fitting the body through openings are recalibrated without feedback from practicing the action; locomotion exploration is sufficient. The present study used a different fitting task, squeezing through doorways, to determine whether locomotor experience was sufficient for recalibrating to changes in body size that altered affordances. Participants were unable to recalibrate from locomotor experience, demonstrating that exploratory behaviors do not necessarily generalize between functionally similar affordances. Participants only recalibrated following action practice or after receiving feedback about judgment accuracy, suggesting that the informational requirements of the squeezing task may differ from those of other fitting tasks. Implications for affordance theory are discussed.

Designing Smart Objects to Support Affording Situations: Exploiting Affordance Through an Understanding of Forms of Engagement

In this paper I consider how the concept of “affordance” has been adapted from the original writings of Gibson and applied to interaction design. I argue that a clear understanding of affordance shifts the goal of interaction design from one of solely focusing on either the physical object or the capabilities of the person, toward an understanding of interactivity. To do this, I develop the concept of Forms of Engagement, originally proposed to account for tool use. Finally, I extend this concept to interacting with modified tangible user interfaces, or “animate objects.” These animate objects not only sense how they are being used, but also communicate with each other to develop a shared intent, and provide prompts and cues to encourage specific actions. In this way, the human-object-environment system creates affording situations in pursuit of shared intentions and goals. In order to determine when to provide prompts and cues, the objects need to have a model of how they ought to be used and what intention they are being used to achieve. Consequently, affordances become not only the means by which actions are encouraged but also the manner in which intentions are identified and agreed.

Trapped in a tight spot: Scaling effects occur when, according to the action-specific account, they should not, and fail to occur when they should

The action-specific account of perception claims that what we see is perceptually scaled according to our action capacity. However, it has been argued that this account relies on an overly confirmatory research strategy—predicting the presence of, and then finding, an effect (Firestone & Scholl, 2014). A comprehensive approach should also test disconfirmatory predictions, in which no effect is expected. In two experiments, we tested one such prediction based on the action-specific account, namely that scaling effects should occur only when participants intend to act (Witt, Proffitt, & Epstein, 2005). All participants wore asymmetric gloves in which one glove was padded with extra material, so that one hand was wider than the other. Participants visually estimated the width of apertures. The action-specific account predicts that the apertures should be estimated as being narrower for the wider hand, but only when participants intend to act. We found this scaling effect when it should not have occurred (Exp. 1, for participants who did not intend to act), as well as no effect when it should have occurred (Exp. 2, for participants who intended to act but were given a cover story for the visibility and position of their hands). Thus, the cover story used in Experiment 2 eliminated the scaling effect found in Experiment 1. We suggest that the scaling effect observed in Experiment 1 likely resulted from demand characteristics associated with using a salient, unexplained manipulation (e.g., telling people which hand to use to do the task). Our results suggest that the action-specific account lacks predictive power.

Does grasping capacity influence object size estimates? It depends on the context

Linkenauger, Witt, and Proffitt (Journal of Experimental Psychology: Human Perception and Performance, 37(5), 1432–1441, 2011, Experiment 2) reported that right-handers estimated objects as smaller if they intended to grasp them in their right rather than their left hand. Based on the action-specific account, they argued that this scaling effect occurred because participants believed their right hand could grasp larger objects. However, Collier and Lawson (Journal of Experimental Psychology: Human Perception and Performance, 43(4), 749–769, 2017) failed to replicate this effect. Here, we investigated whether this discrepancy in results arose from demand characteristics. We investigated two forms of demand characteristics: altering responses following conscious hypothesis guessing (Experiments 1 and 2), and subtle influences of the experimental context (Experiment 3). We found no scaling effects when participants were given instructions which implied the expected outcome of the experiment (Experiment 1), but they were obtained when we used unrealistically explicit instructions which gave the exact prediction made by the action-specific account (Experiment 2). Scaling effects were also found using a context in which grasping capacity could seem relevant for size estimation (by asking participants about the perceived graspability of an object immediately before asking about its size on every trial, as was done in Linkenauger et al., 2011; Experiment 2). These results suggest that demand characteristics due to context effects could explain the scaling effects reported in Experiment 2 of Linkenauger et al. (2011), rather than either hypothesis guessing, or, as proposed by the action-specific account, a change in the perceived size of objects.

It's out of my hands! Grasping capacity may not influence perceived object size

Linkenauger, Witt, and Proffitt (2011) found that the perceived size of graspable objects was scaled by perceived grasping capacity. However, it is possible that this effect occurred because object size was estimated on the same trial as grasping capacity. This may have led to a conflation of estimates of perceived action capacity and spatial properties. In 5 experiments, we tested Linkenauger et al.’s claim that right-handed observers overestimate the grasping capacity of their right hand relative to their left hand, and that this, in turn, leads them to underestimate the size of objects to-be-grasped in their right hand relative to their left hand. We replicated the finding that right handers overestimate the size and grasping capacity of their right hand relative to their left hand. However, when estimates of object size and grasping capacity were made in separate tasks, objects grasped in the right hand were not underestimated relative to those grasped in the left hand. Further, when grasping capacity was physically restricted, observers appropriately recalibrated their perception of their maximum grasp but estimates of object size were unaffected. Our results suggest that changes in action capacity may not influence perceived object size if sources of conflation are controlled for.

The action-specific account of perception suggests that an observer’s capacity for action scales how the environment appears to them and, specifically, how they perceive its spatial properties. However, contrary to the predictions of this account, the results of the present studies suggest that perceived object size is not influenced by either actual or perceived grasping capacity. First, although right handers perceived their right hand to be both larger and to have a greater grasping capacity than their left hand, size estimates for an object were not influenced by which hand was used to grasp that object. Second, in a stronger manipulation, we reduced both the actual and the perceived grasping capacity of one hand by taping its fingers together. Despite this causing a substantial reduction in action capacity, it did not influence estimates of object size. These results show that action capacity and spatial properties can be perceived independently.

Walking through Apertures in Individuals with Stroke

Objective

Walking through a narrow aperture requires unique postural configurations, i.e., body rotation in the yaw dimension. Stroke individuals may have difficulty performing the body rotations due to motor paralysis on one side of their body. The present study was therefore designed to investigate how successfully such individuals walk through apertures and how they perform body rotation behavior.

Method

Stroke fallers (n = 10), stroke non-fallers (n = 13), and healthy controls (n = 23) participated. In the main task, participants walked for 4 m and passed through apertures of various widths (0.9–1.3 times the participant’s shoulder width). Accidental contact with the frame of an aperture and kinematic characteristics at the moment of aperture crossing were measured. Participants also performed a perceptual judgment task to measure the accuracy of their perceived aperture passability.

Results and Discussion

Stroke fallers made frequent contacts on their paretic side; however, the contacts were not frequent when they penetrated apertures from their paretic side. Stroke fallers and non-fallers rotated their body with multiple steps, rather than a single step, to deal with their motor paralysis. Although the minimum passable width was greater for stroke fallers, the body rotation angle was comparable among groups. This suggests that frequent contact in stroke fallers was due to insufficient body rotation. The fact that there was no significant group difference in the perceived aperture passability suggested that contact occurred mainly due to locomotor factors rather than perceptual factors. Two possible explanations (availability of vision and/or attention) were provided as to why accidental contact on the paretic side did not occur frequently when stroke fallers penetrated the apertures from their paretic side.