The direction of walking--but not throwing or kicking--is adapted by optic flow

Systemic Effects of Molar and Incisor Biting on Walking Direction With and Without Visual Feedback

Gait stability and walking direction control are conventionally attributed to coordination among somatosensory, visual, and vestibular systems. Recent evidence of functional interdependence between masticatory and neuromuscular systems indicates that the stomatognathic system is neurologically integrated with various body systems relevant to movement planning and execution. This study investigated the effects of unilateral molar biting and incisor biting on walking with and without visual feedback. A cohort of 31 healthy young adults aged 21 to 30 years (average age of 23.93 ± 1.89) participated in this study. Three types of errors in walking direction (angle error, position error, and curve error) were computed. Our findings indicate that, in right-handed individuals, irrespective of visual feedback, unilateral biting caused systematic deviations toward the biting side from initiation to termination of walking. The consistent deviation in walking, particularly during unilateral right biting conditions in right-handed individuals, may indicate a complex interplay between masticatory function and gait control mechanism, potentially influenced by handedness and motor lateralization within the cortex. This study establishes a foundation for future research exploring the interrelation between bite location, visual feedback, and motor control in diverse populations. This research may provide insight for more efficient interventions for gait-related disorders.

Jumping and leaping estimations using optic flow

Optic flow provides information on movement direction and speed during locomotion. Changing the relationship between optic flow and walking speed via training has been shown to influence subsequent distance and hill steepness estimations. Previous research has shown that experience with slow optic flow at a given walking speed was associated with increased effort and distance overestimation in comparison to experiencing with fast optic flow at the same walking speed. Here, we investigated whether exposure to different optic flow speeds relative to gait influences perceptions of leaping and jumping ability. Participants estimated their maximum leaping and jumping ability after exposure to either fast or moderate optic flow at the same walking speed. Those calibrated to fast optic flow estimated farther leaping and jumping abilities than those calibrated to moderate optic flow. Findings suggest that recalibration between optic flow and walking speed may specify an action boundary when calibrated or scaled to actions such as leaping, and possibly, the manipulation of optic flow speed has resulted in a change in the associated anticipated effort for walking a prescribed distance, which in turn influence one's perceived action capabilities for jumping and leaping.

Targeted reaching with monocular depth information and haptic feedback: Comparing between monocular patients and normally sighted observers

Monocular blindness impairs visual depth perception, yet patients seldom report difficulties in targeted actions like reaching, walking, or driving. We hypothesized that by utilizing monocular depth information and calibrating actions with haptic feedback, monocular patients can perceive egocentric distance and perform targeted actions. We compared targeted reaching in monocular patients, monocular-viewing, and binocular-viewing normal controls. Sixty observers reached either a far or a near target, calibrating reaches to the near target with accurate or false feedback while leaving reaches to the far target uncalibrated. Reaching accuracy and precision were analyzed. Results indicated no difference in reaching accuracy between monocular patients and normal controls; all groups initially underestimated distances before until calibration. Monocular patients responded to calibration sensitively, achieving accuracy in calibrated reaches and generalizing this effect to uncalibrated distances. Thus, with monocular depth information and haptic feedback, monocular patients could perceive distance and accomplish targeted reaching.

Ubiquitous skill opens opportunities for talent and expertise development

In this article we aim to define and present the complementary nature of talent, skill and expertise. Human daily life is replete with expressions of skillful behaviours while interacting with the world, which in specific socio-culturally defined domains, such as sport and work, demand a specialization of such ubiquitous skill. Certain manifestations of ubiquitous skill are identified by experts from the specialized domain of sport with the label of "talent". In this paper we propose that "talent" is thus socially defined, considered identifiable at an early age and forms the basis for selection and entry at the starting point in domains like sport. Once an individual, defined as "talented" enters the "pathway" for participating in the sport domain, there begins an intense socialization process where training, evaluation, institutionalization and framing takes place for continued development of such talent. This is the formalised process of working on ubiquitous skills refining and changing them into specialized skills in sport. An ecological dynamics rationale is used to explain that this specialization approach is developed through a process of expert skill learning, which entails the stages of exploration and education of intention stabilization and perceptual attunement, and exploitation and calibration. Skill learning aims to develop potentiality and its expression in actuality, i.e., how learning is expressed in contextualized expert performance.

Perception of object motion during self-motion: Correlated biases in judgments of heading direction and object motion

This study investigated the relationship between perceived heading direction and perceived motion of an independently moving object during self-motion. Using a dual task paradigm, we tested whether object motion judgments showed biases consistent with heading perception, both across conditions and from trial to trial. Subjects viewed simulated self-motion and estimated their heading direction (Experiment 1), or walked toward a target in virtual reality with conflicting physical and visual cues (Experiment 2). During self-motion, an independently moving object briefly appeared, with varied horizontal velocity, and observers judged whether the object was moving leftward or rightward. In Experiment 1, heading estimates showed an expected center bias, and object motion judgments showed corresponding biases. Trial-to-trial variations were also correlated: on trials with a more rightward heading bias, object motion judgments were consistent with a more rightward heading, and vice versa. In Experiment 2, we estimated the relative weighting of visual and physical cues in control of walking and object motion judgments. Both were strongly influenced by nonvisual cues, with less weighting for object motion (86% vs. 63%). There were also trial-to-trial correlations between biases in walking direction and object motion judgments. The results provide evidence that shared mechanisms contribute to heading perception and perception of object motion.

Development of motion speed perception from infancy to early adulthood: a high-density EEG study of simulated forward motion through optic flow

This study investigated evoked and oscillatory brain activity in response to forward visual motion at three different ecologically valid speeds, simulated through an optic flow pattern consisting of a virtual road with moving poles at either side of it. Participants were prelocomotor infants at 4–5 months, crawling infants at 9–11 months, primary school children at 6 years, adolescents at 12 years, and young adults. N2 latencies for motion decreased significantly with age from around 400 ms in prelocomotor infants to 325 ms in crawling infants, and from 300 and 275 ms in 6- and 12-year-olds, respectively, to 250 ms in adults. Infants at 4–5 months displayed the longest latencies and appeared unable to differentiate between motion speeds. In contrast, crawling infants at 9–11 months and 6-year-old children differentiated between low, medium and high speeds, with shortest latency for low speed. Adolescents and adults displayed similar short latencies for the three motion speeds, indicating that they perceived them as equally easy to detect. Time–frequency analyses indicated that with increasing age, participants showed a progression from low- to high-frequency desynchronized oscillatory brain activity in response to visual motion. The developmental differences in motion speed perception are interpreted in terms of a combination of neurobiological development and increased experience with self-produced locomotion. Our findings suggest that motion speed perception is not fully developed until adolescence, which has implications for children’s road traffic safety.

Different generalization of fast and slow visuomotor adaptation across locomotion and pointing tasks

Sensorimotor adaptation can involve multiple learning processes with different time courses, and these processes may have different patterns of transfer. In this study, we tested how slow learning and fast learning transfer across tasks, and the specificity of transfer. We tested two natural goal-directed tasks: pointing and walking toward a visible target. We also tested a novel "hand locomotion" task in which subjects used pointing movements to cause simulated self-motion in virtual reality. The hand locomotion task used the same physical movement as pointing, but performed the same function as stepping. During an experimental block, subjects performed alternating training trials with perturbed visual feedback and test trials with no feedback. The test trials were either the same task to measure adaptation, or a different task to measure transfer. Perturbations on adaptation trials varied over time as a sum of sinusoids with different frequencies. Fast learning would be expected to produce equal responses to fast and slow perturbations, while slower learning would dampen responses to higher frequency perturbations. Subjects were generally not aware of the smoothly varying perturbations, but showed detectable adaptation for all three tasks. Only pointing produced significantly different responses to high- and low-frequency perturbations, consistent with slow learning. Adaptation of pointing produced more transfer to the hand locomotion task, which shared the same effector and motor actions, than to the stepping task. The other tasks showed fast learning but little or no slow learning, and equal transfer to tasks with different effector or function. Our results suggest that the slower components of sensorimotor adaptation are more movement specific, while faster learning is more generalizable.

The effects of testing environment, experimental design, and ankle loading on calibration to perturbed optic flow during locomotion

Calibration is the process by which the execution of actions becomes scaled to the (changing) relationship between environmental features and the actor's action capabilities. Though much research has investigated how individuals calibrate to perturbed optic flow, it remains unclear how different experimental factors contribute to the magnitude of calibration transfer. In the present study, we assessed how testing environment (Experiment 1), an adapted pretest-calibration-posttest design (Experiment 2), and bilateral ankle loading (Experiment 3) affected the magnitude of calibration to perturbed optic flow. We found that calibration transferred analogously to real-world and virtual environments. Although the magnitude of calibration transfer found here was greater than that reported by previous researchers, it was evident that calibration occurred rapidly and quickly plateaued, further supporting the claim that calibration is often incomplete despite continued calibration trials. We also saw an asymmetry in calibration magnitude, which may be due to a lack of appropriate perceptual-motor scaling prior to calibration. The implications of these findings for the assessment of distance perception and calibration in real-world and virtual environments are discussed.

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.

Shrinking Circles: Adaptation to Increased Curvature Gain in Redirected Walking

Real walking is the most natural way to locomote in virtual reality (VR), but a confined physical walking space limits its applicability. Redirected walking (RDW) is a collection of techniques to solve this problem. One of these techniques aims to imperceptibly rotate the user's view of the virtual scene in order to steer her along a confined path whilst giving the impression of walking in a straight line in a large virtual space. Measurement of perceptual thresholds for the detection of such a modified curvature gain have indicated a radius that is still larger than most room sizes. Since the brain is an adaptive system and thresholds usually depend on previous stimulations, we tested if prolonged exposure to an immersive virtual environment (IVE) with increased curvature gain produces adaptation to that gain and modifies thresholds such that, over time, larger curvature gains can be applied for RDW. Therefore, participants first completed a measurement of their perceptual threshold for curvature gain. In a second session, the same participants were exposed to an IVE with a constant curvature gain in which they walked between two targets for about 20 minutes. Afterwards, their perceptual thresholds were measured again. The results show that the psychometric curves shifted after the exposure session and perceptual thresholds for increased curvature gain further increased. The increase of the detection threshold suggests that participants adapt to the manipulation and stronger curvature gains can be applied in RDW, and therefore improves its applicability in such situations.

A high-density EEG study of differentiation between two speeds and directions of simulated optic flow in adults and infants

A high-density EEG study was carried out to investigate cortical activity in response to forward and backward visual motion at two different driving speeds, simulated through optic flow. Participants were prelocomotor infants at the age of 4-5 months and infants with at least 3 weeks of crawling experience at the age of 8-11 months, and adults. Adults displayed shorter N2 latencies in response to forward as opposed to backward visual motion and differentiated significantly between low and high speeds, with shorter latencies for low speeds. Only infants at 8-11 months displayed similar latency differences between motion directions, and exclusively in response to low speed. The developmental differences in latency between infant groups are interpreted in terms of a combination of increased experience with self-produced locomotion and neurobiological development. Analyses of temporal spectral evolution (TSE, time-dependent amplitude changes) were also performed to investigate nonphase-locked changes at lower frequencies in underlying neuronal networks. TSE showed event-related desynchronization activity in response to visual motion for infants compared to adults. The poorer responses in infants are probably related to immaturity of the dorsal visual stream specialized in the processing of visual motion and could explain the observed problems in infants with differentiating high speeds of up to 50 km/h.

Anxiety Influences the Perceptual-Motor Calibration of Visually Guided Braking to Avoid Collisions

We investigated whether anxiety influences perceptual-motor calibration in a braking to avoid a collision task. Participants performed either a discrete braking task (Experiment 1) or a continuous braking task (Experiment 2), with the goal of stopping before colliding with a stop sign. Half of participants performed the braking task after an anxiety induction. We investigated whether anxiety reduced the frequency of crashing and if it influenced the calibration of perception (visual information) and action (brake pressure) dynamically between-trials in Experiment 1 and within-trials in Experiment 2. In the discrete braking task, anxious participants crashed less often and made larger corrective adjustments trial-to-trial after crashing, suggesting that the influence of anxiety on behavior did not occur uniformly, but rather dynamically with anxiety amplifying the reaction to previous crashes. However, when performing continuous braking, anxious participants crashed more often, and their within-trial adjustments of deceleration were less related to visual information compared to controls. Taken together, these findings suggest that the timescale and nature of the task mediates the influence of anxiety on the performance of goal-directed actions.

Locomotive Recalibration and Prism Adaptation of Children and Teens in Immersive Virtual Environments

As virtual reality expands in popularity, an increasingly diverse audience is gaining exposure to immersive virtual environments (IVEs). A significant body of research has demonstrated how perception and action work in such environments, but most of this work has been done studying adults. Less is known about how physical and cognitive development affect perception and action in IVEs, particularly as applied to preteen and teenage children. Accordingly, in the current study we assess how preteens (children aged 8-12 years) and teenagers (children aged 15-18 years) respond to mismatches between their motor behavior and the visual information presented by an IVE. Over two experiments, we evaluate how these individuals recalibrate their actions across functionally distinct systems of movement. The first experiment analyzed forward walking recalibration after exposure to an IVE with either increased or decreased visual flow. Visual flow during normal bipedal locomotion was manipulated to be either twice or half as fast as the physical gait. The second experiment leveraged a prism throwing adaptation paradigm to test the effect of recalibration on throwing movement. In the first experiment, our results show no differences across age groups, although subjects generally experienced a post-exposure effect of shortened distance estimation after experiencing visually faster flow and longer distance estimation after experiencing visually slower flow. In the second experiment, subjects generally showed the typical prism adaptation behavior of a throwing after-effect error. The error lasted longer for preteens than older children. Our results have implications for the design of virtual systems with children as a target audience.

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.

Auditory environmental context affects visual distance perception

In this article, we show that visual distance perception (VDP) is influenced by the auditory environmental context through reverberation-related cues. We performed two VDP experiments in two dark rooms with extremely different reverberation times: an anechoic chamber and a reverberant room. Subjects assigned to the reverberant room perceived the targets farther than subjects assigned to the anechoic chamber. Also, we found a positive correlation between the maximum perceived distance and the auditorily perceived room size. We next performed a second experiment in which the same subjects of Experiment 1 were interchanged between rooms. We found that subjects preserved the responses from the previous experiment provided they were compatible with the present perception of the environment; if not, perceived distance was biased towards the auditorily perceived boundaries of the room. Results of both experiments show that the auditory environment can influence VDP, presumably through reverberation cues related to the perception of room size.

The Anatomy of Action Systems: Task Differentiation When Learning an EMG Controlled Game

This study aims to determine to what extent the task for an action system in its initial development relies on functional and anatomical components. Fifty-two able-bodied participants were randomly assigned to one of three experimental groups or to a control group. As a pre- and post-test all groups performed a computer game with the same goal and using the same musculature. One experimental group also trained to perform this test, while the other two experimental groups learned to perform a game that differed either in its goal or in the musculature used. The observed change in accuracy indicated that retaining the goal of the task or the musculature used equally increased transfer performance relative to controls. Conversely, changing either the goal or the musculature equally decreased transfer relative to training the test. These results suggest that in the initial development of an action system, the task to which the system pertains is not specified solely by either the goal of the task or the anatomical structures involved. It is suggested that functional specificity and anatomical dependence might equally be outcomes of continuously differentiating activity.

Action potential influences spatial perception: Evidence for genuine top-down effects on perception

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.

The Independent Perceptual Calibration of Action-Neutral and -Referential Environmental Properties

Two experiments were conducted to explore how the calibration of perception of environmental properties taken with reference to an animal and their action capabilities (e.g., affordances) and those that are independent of action capabilities (e.g., metric properties) relate. In both experiments, participants provided reports of the maximum height they could reach above their head with a number of different stick(s) (reach-with-stick height) and the length of those stick(s), a property that is a constituent of reach-with-stick height. In Experiment 1 reach-with-stick height reports improved over trials whereas stick length reports remained constant. In Experiment 2, feedback about maximum reach-with-stick height improved perception of this affordance, but such improvements did not transfer to perception of stick length in a pretest/practice task/posttest design. The results suggest that the perceptual calibration with practice perceiving or feedback about actual dimensions of action-referential and action-neutral properties do not necessarily depend on one another.

A high-density EEG study of differences between three high speeds of simulated forward motion from optic flow in adult participants

A high-density EEG study was conducted to investigate evoked and oscillatory brain activity in response to high speeds of simulated forward motion. Participants were shown an optic flow pattern consisting of a virtual road with moving poles at either side of it, simulating structured forward motion at different driving speeds (25, 50, and 75 km/h) with a static control condition between each motion condition. Significant differences in N2 latencies and peak amplitudes between the three speeds of visual motion were found in parietal channels of interest P3 and P4. As motion speed increased, peak latency increased while peak amplitude decreased which might indicate that higher driving speeds are perceived as more demanding resulting in longer latencies, and as fewer neurons in the motion sensitive areas of the adult brain appear to be attuned to such high visual speeds this could explain the observed inverse relationship between speed and amplitude. In addition, significant differences between alpha de-synchronizations for forward motion and alpha synchronizations in the static condition were found in the parietal midline (PM) source. It was suggested that the alpha de-synchronizations reflect an activated state related to the visual processing of simulated forward motion, whereas the alpha synchronizations in response to the static condition reflect a deactivated resting period.

Perception of maximum stepping and leaping distance: Stepping affordances as a special case of leaping affordances

Successfully performing everyday behaviors requires perceiving affordances-possibilities for behavior that depend on the fit between environmental properties and action capabilities. Whereas affordances for some behaviors are primarily constrained by relatively static geometric properties of the perceiver (non-launching behaviors such as stepping), others are additionally constrained by dynamic force production capabilities of the perceiver (launching behaviors such as leaping). This experiment used a transfer of calibration paradigm to investigate whether visual perception of launching and non-launching behaviors represent independent perception-action tasks. In particular, we investigated whether calibration of visual perception of maximum leaping distance transferred to visual perception of maximum stepping distance, and/or vice versa. The results showed that calibration of perception of maximum leaping distance transferred to perception of maximum stepping distance, suggesting that perception of launching and non-launching are not independent. Rather, perception of stepping affordances may be a special case of perception of leaping affordances.

Reliability and relative weighting of visual and nonvisual information for perceiving direction of self-motion during walking

Direction of self-motion during walking is indicated by multiple cues, including optic flow, nonvisual sensory cues, and motor prediction. I measured the reliability of perceived heading from visual and nonvisual cues during walking, and whether cues are weighted in an optimal manner. I used a heading alignment task to measure perceived heading during walking. Observers walked toward a target in a virtual environment with and without global optic flow. The target was simulated to be infinitely far away, so that it did not provide direct feedback about direction of self-motion. Variability in heading direction was low even without optic flow, with average RMS error of 2.4°. Global optic flow reduced variability to 1.9°-2.1°, depending on the structure of the environment. The small amount of variance reduction was consistent with optimal use of visual information. The relative contribution of visual and nonvisual information was also measured using cue conflict conditions. Optic flow specified a conflicting heading direction (±5°), and bias in walking direction was used to infer relative weighting. Visual feedback influenced heading direction by 16%-34% depending on scene structure, with more effect with dense motion parallax. The weighting of visual feedback was close to the predictions of an optimal integration model given the observed variability measures.

The dynamics of sensorimotor calibration in reaching-to-grasp movements

Reach-to-grasp movements require information about the distance and size of target objects. Calibration of this information could be achieved via feedback information (visual and/or haptic) regarding terminal accuracy when target objects are grasped. A number of reports suggest that the nervous system alters reach-to-grasp behavior following either a visual or haptic error signal indicating inaccurate reaching. Nevertheless, the reported modification is generally partial (reaching is changed less than predicted by the feedback error), a finding that has been ascribed to slow adaptation rates. It is possible, however, that the modified reaching reflects the system's weighting of the visual and haptic information in the presence of noise rather than calibration per se. We modeled the dynamics of calibration and showed that the discrepancy between reaching behavior and the feedback error results from an incomplete calibration process. Our results provide evidence for calibration being an intrinsic feature of reach-to-grasp behavior.

Humans perceive object motion in world coordinates during obstacle avoidance

A fundamental question about locomotion in the presence of moving objects is whether movements are guided based upon perceived object motion in an observer-centered or world-centered reference frame. The former captures object motion relative to the moving observer and depends on both observer and object motion. The latter captures object motion relative to the stationary environment and is independent of observer motion. Subjects walked through a virtual environment (VE) viewed through a head-mounted display and indicated whether they would pass in front of or behind a moving obstacle that was on course to cross their future path. Subjects' movement through the VE was manipulated such that object motion in observer coordinates was affected while object motion in world coordinates was the same. We found that when moving observers choose routes around moving obstacles, they rely on object motion perceived in world coordinates. This entails a process, which has been called flow parsing (Rushton & Warren, 2005; Warren & Rushton, 2009a), that recovers the component of optic flow due to object motion independent of self-motion. We found that when self-motion is real and actively generated, the process by which object motion is recovered relies on both visual and nonvisual information to factor out the influence of self-motion. The remaining component contains information about object motion in world coordinates that is needed to guide locomotion.

Calibration is both functional and anatomical

Bingham and Pagano (1998) described calibration as a mapping from embodied perceptual units to an embodied action unit and suggested that it is an inherent component of perception/action that yields accurate targeted actions. We tested two predictions of this "Mapping Theory." First, calibration should transfer between limbs, because it involves a mapping from perceptual units to an action unit, and thus is functionally specific to the action (Pan, Coats, and Bingham, 2014). We used distorted haptic feedback to calibrate feedforward right hand reaches and tested right and left hand reaches after calibration. The calibration transferred. Second, the Mapping Theory predicts that limb specific calibration should be possible because the units are embodied and anatomy contributes to their scaling. Limbs must be calibrated to one another given potential anatomical differences among limbs. We used distorted haptic feedback to calibrate feedforward reaches with right and left arms simultaneously in opposite directions relative to a visually specified target. Reaches tested after calibration revealed reliable limb specific calibration. Both predictions were confirmed. This resolves a prevailing controversy as to whether calibration is functional (Bruggeman & Warren, 2010; Rieser, Pick, Ashmead, & Garing, 1995) or anatomical (Durgin et al., 2003; Durgin & Pelah, 1999). Necessarily, it is both.

Does perceptual-motor calibration generalize across two different forms of locomotion? Investigations of walking and wheelchairs

The relationship between biomechanical action and perception of self-motion during walking is typically consistent and well-learned but also adaptable. This perceptual-motor coupling can be recalibrated by creating a mismatch between the visual information for self-motion and walking speed. Perceptual-motor recalibration of locomotion has been demonstrated through effects on subsequent walking without vision, showing that learned perceptual-motor coupling influences a dynamic representation of one's spatial position during walking. Our present studies test whether recalibration of wheelchair locomotion, a novel form of locomotion for typically walking individuals, similarly influences subsequent wheelchair locomotion. Furthermore, we test whether adaptation to the pairing of visual information for self-motion during one form of locomotion transfers to a different locomotion modality. We find strong effects of perceptual-motor recalibration for matched locomotion modalities--walking/walking and wheeling/wheeling. Transfer across incongruent locomotion modalities showed weak recalibration effects. The results have implications both for theories of perceptual-motor calibration mechanisms and their effects on spatial orientation, as well as for practical applications in training and rehabilitation.

Transfer of calibration in dynamic touch: what do perceivers learn when they learn about length of a wielded object?

Successfully performing everyday behaviours requires that perceptions and actions are properly calibrated to environmental properties. In three experiments, the authors tested whether calibration was specific to perception of a particular property of a wielded object from a particular grasp position on that object. The experiments investigate whether transfer of recalibration occurs across changes in grasp position (Experiment 1), object property (Experiment 2), and grasp position and object property (Experiment 3). The results suggest that a complete transfer of recalibration occurred in each case. Such results are consistent with recent research on dynamic touch and suggest that rather than recalibrating participants to one particular property of the wielded objects, feedback about a particular property served to recalibrate participants to the properties of the rod set as a whole.