Raôul R. D. Oudejans

The relevance of action in perceiving affordances: Perception of catchableness of fly balls

The catchableness of a fly ball depends on whether the catcher can get to the ball in time; accurate judgments of catchableness must reflect both spatial and temporal aspects. Two experiments examined the perception of catchableness under conditions of restricted information pickup. Experiment 1 compared perceptual judgments with actual catching and revealed that stationary observers are poor perceivers of catchableness, as would be expected by the lack of information about running capabilities. In Experiment 2, participants saw the 1st part of ball trajectories before their vision was occluded. In 1 condition, they started to run (as if to catch the ball) before occlusion; in another, they remained stationary. Moving judgments were better than stationary judgments. This supports the idea that perceiving affordances that depend on kinematic, rather than merely geometric, body characteristics may require the relevant action to be performed.

Information and action in punching a falling ball

Lee, Young, Reddish, Lough, and Clayton (1983) reported that the timing control of jumping and vertically punching a dropping ball exploits the inverse of the rate of change of optical expansion, τ (r). We raise a number of methodological and logical criticisms against their experiment and conclusions and attempt to rectify them by examining elbow joint angles only, in seated punchers, under both monocular and binocular conditions, with two ball sizes, dropped from two heights. Differences between the binocular and monocular cases suggest the exploitation of different information. We present several techniques to help determine the operative variable(s) controlling the action. The optical variable used to initiate and guide flexion appeared to be expansion velocity (looming), rather than τ (r); extension appeared to be under the control of different variables in the monocular and binocular cases. Simulations using single variables and single perceptuo-motor intervals were of mixed success.

Anxiety–performance relationships in climbing: a process-oriented approach

Abstract Objectives : Two experiments were conducted to investigate manifestations of anxiety at the subjective, physiological, and behavioural level of analysis. Design : In Experiment 1 we investigated the manifestations of state anxiety at the first two levels by comparing low- and high-anxiety conditions during climbing. In Experiment 2 we explored behavioural differences under these conditions. Methods : We manipulated anxiety by using a climbing wall with routes defined at different heights (low and high). Participants were 13 and 17 novice climbers in Experiments 1 and 2, respectively (ages 19–30 years). We measured self-reported state anxiety, heart rate (Experiments 1 and 2), blood lactate concentration and muscle fatigue (Experiment 1), and climbing time and fluency of movements (Experiment 2). Results : At the level of subjective experience we found that when novices climbed a route high on a climbing wall they reported significantly more anxiety than when they traversed an identical route low on the climbing wall. At the physiological level, they exhibited significantly higher heart rates, more muscle fatigue, and higher blood lactate concentrations. The results of Experiment 2 showed that state anxiety also affected participants’ movement behaviour, which was evidenced by an increased geometric index of entropy and by longer climbing times. Conclusions : Results indicated that anxiety indeed manifested itself at three levels. A possible explanation for the effects of anxiety that is also found in the literature is that a temporary regress may occur to a movement execution that is associated with earlier stages of motor learning.

Anxiety-induced changes in movement behaviour during the execution of a complex whole-body task

We investigated the impact of anxiety on movement behaviour during the execution of a complex perceptual-motor task. Masters’ (1992) conscious processing hypothesis suggests that under pressure an inward focus of attention occurs, resulting in more conscious control of the movement execution of well-learned skills. The conscious processes interfere with automatic task execution hereby inducing performance decrements. Recent empirical support for the hypothesis has focused on the effects of pressure on end performance. It has not been tested so far whether the changes in performance are also accompanied by changes in movement execution that would be expected following Masters’ hypothesis. In the current study we tested the effects of anxiety on climbing movements on a climbing wall. Two identical traverses at different heights on a climbing wall provided different anxiety conditions. In line with the conscious processing hypothesis we found that anxiety had a significant effect on participants’ movement behaviour evidenced by increases in climbing time and the number of explorative movements (Experiments 1 and 2) and by longer grasping of the holds and slower movements (Experiment 2). These results provide additional support for the conscious processing hypothesis and insight into the relation between anxiety, performance, and movement behaviour.

Aiming at a far target under different viewing conditions: Visual control in basketball jump shooting

Most research on visual search in aiming at far targets assumes preprogrammed motor control implying that relevant visual information is detected prior to the final shooting or throwing movements. Eye movement data indirectly support this claim for stationary tasks. Using the basketball jump shot as experimental task we investigated whether in dynamic tasks in which the target can be seen until ball release, continuous, instead of preprogrammed, motor control is possible. We tested this with the temporal occlusion paradigm: 10 expert shooters took shots under four viewing conditions, namely, no vision, full vision, early vision (vision occluded during the final +/-350 ms before ball release), and late vision (vision occluded until these final +/-350 ms). Late-vision shooting appeared to be as good as shooting with full vision while early-vision performance was severely impaired. The results imply that the final shooting movements were controlled by continuous detection and use of visual information until ball release. The data further suggest that visual and movement control of aiming at a far target develop in close correspondence with the style of execution.

Training with anxiety has a positive effect on expert perceptual-motor performance under pressure

In two experiments, we examined whether training with anxiety can prevent choking in experts performing perceptual–motor tasks. In Experiment 1, 17 expert basketball players practised free throws over a 5-week period with or without induced anxiety. Only after training with anxiety did performance no longer deteriorate during the anxiety posttest. In Experiment 2, 17 expert dart players practised dart throwing from a position high or low on a climbing wall, thus with or without anxiety. Again, only after training with anxiety was performance maintained during the anxiety posttest, despite higher levels of anxiety, heart rate, and perceived effort. It is concluded that practising under anxiety can prevent choking in expert perceptual–motor performance, as one acclimatizes to the specific processes accompanying anxiety.

Reality-based practice under pressure improves handgun shooting performance of police officers

The current study examined whether reality-based practice under pressure may help in preventing degradation of handgun shooting performance under pressure for police officers. Using a pre–post–test design, one group of nine police officers practised handgun shooting under pressure evoked by an opponent who also fired back using marking (coloured soap) cartridges. The control group (n = 8) practised handgun shooting on standard cardboard targets instead of real opponents. Within a fortnight after the pre-test, both groups received three training sessions of 1 h, in which each person fired a total of 72 rounds. During the pre- and post test each participant took 30 shots without pressure (cardboard targets) and 30 shots under additional pressure (with an opponent firing back). While during the pre-test both groups performed worse in front of an opponent firing back compared to the cardboard targets, after the training sessions shooting performance of the experimental group no longer deteriorated with an opponent while performance of the control group was equally harmed as during the pre-test. These results indicate that training exercises involving increased pressure can acclimatize shooting performance of ordinary police officers to those situations with elevated pressure that they may encounter during their police work.

Errors in judging ‘offside’ in football

In football (soccer), a player is ‘offside’ if he or she is closer to the goal than the last defender (excluding the goalkeeper) when the ball is passed to them. We investigated why assistant referees, who have the responsibility of judging offside, regularly make mistakes. We show that this is probably due to the angle of viewing by the assistant referee, who is frequently positioned beyond the last defender — a viewpoint from which errors are optically inevitable.

Anxiety and perceptual-motor performance: toward an integrated model of concepts, mechanisms, and processes

Under anxiety, people sometimes perform poorly. This concerns cognitive performance (e.g., taking an important exam) as well as perceptual-motor performance (e.g., picking up a cup from a table). There is still much debate about how anxiety affects perceptual-motor performance. In the current paper we review the experimental literature on anxiety and perceptual-motor performance, thereby focusing on how anxiety affects the perception, selection, and realization of action possibilities. Based on this review we discuss the merits of two opposing theoretical explanations and build on existing frameworks of anxiety and cognitive performance to develop an integrated model that explains the various ways in which anxiety may specifically affect perceptual-motor performance. This model distinguishes between positive and negative effects of anxiety and, moving beyond previous approaches, recognizes three operational levels (i.e., attentional, interpretational, and behavioral) at which anxiety may affect different aspects of goal-directed action. Finally, predictions are formulated and directions for future research suggested.

Effects of anxiety on handgun shooting behavior of police officers: A pilot study

Abstract The current pilot study aimed at providing an initial assessment of how anxiety influences police officers’ shooting behavior. Seven police officers participated and completed an identical shooting exercise under two experimental conditions: low anxiety, against a non-threatening opponent, and high anxiety (HA), against a threatening opponent who occasionally shot back using colored soap cartridges. Measurements included shooting accuracy, movement times, head/body orientation, and blink behavior. Results showed that under HA, shooting accuracy decreased. Underlying this degradation of performance, participants acted faster and made themselves smaller to reduce the chance of being hit. Furthermore, they blinked more often, leading to increases in the amount of time participants had their eyes closed. Findings provide support for attentional control theory, hereby also pointing to possible interventions to improve police officers’ shooting performance under pressure.