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Almost all locomotor animals are sensitive to optical expansion (visual looming) and for most animals this sensitivity is evident very early in their development. In humans there is evidence that responses to looming stimuli begin in the first 6 weeks of life, but here we demonstrate that as children become independent their perceptual acuity needs to be 50 to 100 times better than has been demonstrated in infants in order to be skilful at collision avoidance at a roadside. We have recently established that sensitivity to the detection of visual looming in 6- to 11-year-old children is significantly below that of adults (Wann, Poulter & Purcell, 2011). Here, using comparable methods, we explore looming detection sensitivity in children with Developmental Co-ordination Disorder (DCD), who show broad patterns of impairment in visuo-motor control. We presented visual simulations of approaching vehicles, scaled to represent different approach rates, to children with DCD aged between 6 and 11 years (n = 11) and typically developing age and gender matched controls (n = 11). Looming detection thresholds were measured under foveal and perifoveal viewing conditions, for isotropic expansion and isotropic expansion with simulated viewpoint motion. Our results show that there are situations in which children with DCD may fail to detect vehicles approaching at speeds in excess of 22 km/h, suggesting a developmental immaturity in looming sensitivity. This provides one of the first clear demonstrations of low-level motion processing deficits in children with DCD. The decrement observed may give rise to potential errors in the road crossing behaviour of these children, whereby approaching vehicles could be perceived as stationary. These findings further contribute towards understanding the adverse statistic that children under 9 years of age are four times more likely than adults to be involved in a road accident as a pedestrian.

As pedestrians, the perceptual ability to accurately judge the relative rate of approaching vehicles and select a suitable crossing gap requires sensitivity to looming. It also requires that crossing judgments are synchronized with motoric capabilities. Previous research has suggested that children with Developmental Co-ordination Disorder (DCD) may have deficits in visual processing, specifically in detecting visual motion. It is possible, therefore that this population are at greater risk at the roadside. In a series of motion prediction tasks, several component roadside skills were assessed in 15 children with DCD, or at risk of DCD, aged between 6 and 11 years along with 15 typically developing age and gender matched controls. First, threshold errors for relative approach rate judgments (looming) were measured when vehicle size (car or truck) varied. Second, thresholds for crossing gap selection were measured for vehicle approach speeds of 32, 48, 64 and 80 km/h (20-50 mph). These were related to the walking speeds of children of different ages and profiles. We found that children with DCD showed a deficit in making relative approach rate judgments, using looming, which suggests they may not discern that a vehicle is travelling faster than the urban speed limit. Children with DCD also left considerably longer temporal crossing gaps than controls perhaps reflecting a lack of confidence in their ability, these preferred gaps were over twice the average inter-car gaps that occurred on roads around their school. Our findings raise a number of issues concerning children with DCD and their competence and potential limitations as pedestrians. (Contains 1 figure and 5 tables.)

In two experiments, we used an automatic car simulator to examine the steering control, speed regulation and response to hazards of young adults with developmental coordination disorder (DCD) and limited driving experience. In Experiment 1 participants either used the accelerator pedal to regulate their speed, or used the brake pedal when they needed to slow down from a pre-set speed. In Experiment 2, we introduced an auditory distraction condition that shared similarities with maintaining a conversation. Overall, the DCD group produced a larger variance in heading and needed more steering adjustments on straight roads, compared to age-matched controls. When turning bends, the DCD group showed greater difficulty in controlling steering while regulating their speed with the accelerator pedal but this was less problematic when using the brake. The DCD group also responded slower than the control group to pedestrians who walked towards their path. The auditory distraction in Experiment 2 had no visible effects on steering control but increased the reaction times to pedestrians in both groups. We discuss the results in terms of the visuomotor control in steering and the learning of optimal mappings between optic flow and vehicle control. (Contains 4 figures and 1 table.)

The authors examined observers steering through a series of obstacles to determine the role of active gaze in shaping locomotor trajectories. Participants sat on a bicycle trainer integrated with a large field-of-view simulator and steered through a series of slalom gates. Steering behavior was determined by examining the passing distance through gates and the smoothness of trajectory. Gaze monitoring revealed which slalom targets were fixated and for how long. Participants tended to track the most immediate gate until it was about 1.5 s away, at which point gaze switched to the next slalom gate. To probe this gaze pattern, the authors then introduced a number of experimental conditions that placed spatial or temporal constraints on where participants could look and when. These manipulations resulted in systematic steering errors when observers were forced to use unnatural looking patterns, but errors were reduced when peripheral monitoring of obstacles was allowed. A steering model based on active gaze sampling is proposed, informed by the experimental conditions and consistent with observations in free-gaze experiments and with recommendations from real-world high-speed steering.

To steer a course through the world, people are almost entirely dependent on visual information, of which a key component is optic flow. In many models of locomotion, heading is described as the fundamental control variable; however, it has also been shown that fixating points along or near one's future path could be the basis of an efficient control solution. Here, the authors aim to establish how well observers can pinpoint instantaneous heading and path, by measuring their accuracy when looking at these features while traveling along straight and curved paths. The results showed that observers could identify both heading and path accurately (approximately 3 degrees) when traveling along straight paths, but on curved paths they were more accurate at identifying a point on their future path (approximately 5 degrees) than indicating their instantaneous heading (approximately 13 degrees). Furthermore, whereas participants could track changes in the tightness of their path, they were unable to accurately track the rate of change of heading. In light of these results, the authors suggest it is unlikely that heading is primarily used by the visual system to support active steering.

During locomotion, retinal flow, gaze angle, and vestibular information can contribute to one's perception of self-motion. Their respective roles were investigated during active steering: Retinal flow and gaze angle were biased by altering the visual information during computer-simulated locomotion, and vestibular information was controlled through use of a motorized chair that rotated the participant around his or her vertical axis. Chair rotation was made appropriate for the steering response of the participant or made inappropriate by rotating a proportion of the veridical amount. Large steering errors resulted from selective manipulation of retinal flow and gaze angle, and the pattern of errors provided strong evidence for an additive model of combination. Vestibular information had little or no effect on steering performance, suggesting that vestibular signals are not integrated with visual information for the control of steering at these speeds.

Locomoting through the environment typically involves anticipating impending changes in heading trajectory in addition to maintaining the current direction of travel. We explored the neural systems involved in the 'far road' and 'near road' mechanisms proposed by Land and Horwood (1995) using simulated forward or backward travel where participants were required to gauge their current direction of travel (rather than directly control it). During forward egomotion, the distant road edges provided future path information, which participants used to improve their heading judgments. During backward egomotion, the road edges did not enhance performance because they no longer provided prospective information. This behavioral dissociation was reflected at the neural level, where only simulated forward travel increased activation in a region of the superior parietal lobe and the medial intraparietal sulcus. Providing only near road information during a forward heading judgment task resulted in activation in the motion complex. We propose a complementary role for the posterior parietal cortex and motion complex in detecting future path information and maintaining current lane positioning, respectively. Keywords: heading, superior parietal lobe, intraparietal sulcus, motion complex, road features DOI: 10.1037/a0018728

The authors examined observers steering through a series of obstacles to determine the role of active gaze in shaping locomotor trajectories. Participants sat on a bicycle trainer integrated with a large field-of-view simulator and steered through a series of slalom gates. Steering behavior was determined by examining the passing distance through gates and the smoothness of trajectory. Gaze monitoring revealed which slalom targets were fixated and for how long. Participants tended to track the most immediate gate until it was about 1.5 s away, at which point gaze switched to the next slalom gate. To probe this gaze pattern, the authors then introduced a number of experimental conditions that placed spatial or temporal constraints on where participants could look and when. These manipulations resulted in systematic steering errors when observers were forced to use unnatural looking patterns, but errors were reduced when peripheral monitoring of obstacles was allowed. A steering model based on active gaze sampling is proposed, informed by the experimental conditions and consistent with observations in free-gaze experiments and with recommendations from real-world high-speed steering. Keywords: locomotion, steering, gaze, eye movements, active vision

To steer a course through the world, people are almost entirely dependent on visual information, of which a key component is optic flow. In many models of locomotion, heading is described as the fundamental control variable; however, it has also been shown that fixating points along or near one's future path could be the basis of an efficient control solution. Here, the authors aim to establish how well observers can pinpoint instantaneous heading and path, by measuring their accuracy when looking at these features while traveling along straight and curved paths. The results showed that observers could identify both heading and path accurately (~3[degrees]) when traveling along straight paths, but on curved paths they were more accurate at identifying a point on their future path (~5[degrees]) than indicating their instantaneous heading (~13[degrees]). Furthermore, whereas participants could track changes in the tightness of their path, they were unable to accurately track the rate of change of heading. In light of these results, the authors suggest it is unlikely that heading is primarily used by the visual system to support active steering. Keywords: human locomotion, heading, optic flow, eye movements, active gaze

During locomotion, retinal flow, gaze angle, and vestibular information can contribute to one's perception of self-motion. Their respective roles were investigated during active steering: Retinal flow and gaze angle were biased by altering the visual information during computer-simulated locomotion, and vestibular information was controlled through use of a motorized chair that rotated the participant around his or her vertical axis. Chair rotation was made appropriate for the steering response of the participant or made inappropriate by rotating a proportion of the veridical amount. Large steering errors resulted from selective manipulation of retinal flow and gaze angle, and the pattern of errors provided strong evidence for an additive model of combination. Vestibular information had little or no effect on steering performance, suggesting that vestibular signals are not integrated with visual information for the control of steering at these speeds. Keywords: human locomotion, steering, body rotation, vestibular information, semicircular canals, optic flow, gaze angle

INTRODUCTION It is fashionable to label any computer representation of three-dimensional (3D) space as 'virtual reality.' We have previously suggested (Wann & Mon-Williams, 1996) that the term virtual reality (VR) […], It has been demonstrated that a stereoscopic virtual reality system can cause deficits of binocular vision but that a well-engineered bi-ocular (nonstereoscopic) display can avoid causing stress to the visual system. The stereoscopic depth information present in binocular displays has been hypothesized to be a contributing factor to visual stress. We undertook research to determine the effect of stereoscopic depth in virtual reality displays on the visual system and found that stereoscopic depth does not, per se, cause problems to binocular vision over short (10-min) viewing periods. However, 10 min of viewing a display that required constant ocular focus with changing vergence eye movements was sufficient to cause deficits of binocular vision.

A critical review is presented of previous studies that have examined the use of the tau margin ([[Tau].sub.m]) in the temporal judgment of arrival in natural contexts. This body of evidence is frequently cited as providing strong support for the use of [[Tau].sub.m] for interceptive timing. Critical flaws are demonstrated in either the analysis or interpretation of many of these studies. It is suggested that temporal control in a number of these experiments could have been effected using a relative distance estimate ([Zeta] ratio). Results are also presented and discussed that conflict with the [[Tau].sub.m] control hypothesis. It is concluded that although the [[Tau].sub.m] hypothesis provides an appealing account of interceptive timing, its broad acceptance is unwarranted on the evidence available.

The hypothesis of Lee (1976) - that approach and deceleration toward a surface can be controlled through the rate of change of the optic variable Tau - was examined for natural human locomotion. In Experiment 1, 12 adults were asked to perform locomotor tasks that required running at speed and then decelerating so that either the hand or head made a controlled contact with a door. In Experiment 2, 12 preschool children performed a relay-running task that required similar control. In Experiment 3, 12 children and 12 adults ran with a stick as an extension to their arm length and performed the same task. The results supported Lee's hypothesis for the initial phase of approach, but subjects switched to a separate adjustment phase 2 to 3 arm lengths from the target. Children did not adopt an appropriate Tau strategy for collision avoidance and appeared unable to modify their approach strategy to allow for a hand-held stick.

Developmental coordination disorder (DCD) occurs in a small number of children who present with impaired body/eye coordination. No study of ophthalmic function in DCD exists despite vision's primary role in perception. Ocular performance was therefore assessed with a battery of tests. Five hundred children aged between 5 and 7 years were involved in the study. Diagnosis of DCD was confirmed for 29 children by the Movement Assessment Battery for Children (ABC); 29 control children were randomly selected. Comprehensive examination with a battery of ophthalmic tests did not reveal any significant difference in visual status between the two groups. Strabismus was found in 5 children from both groups. All 5 children with strabismus from the DCD group showed a similar movement profile with the Motor Competence Checklist. While a causal relationship cannot be discounted, the presence of strabismus appears more likely to be a "hard" neurological sign of central damage common to this group. The evidence seems to indicate that a simple ophthalmic difficulty does not explain problems with movement control. [ABSTRACT FROM AUTHOR]