F.C. Bakker

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.

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.

Changes in muscular activity while imagining weight lifting using stimulus or response propositions

Investigating emotional imagery, Lang (1977, 1979) proposed a dichotomy between stimulus and response propositions. In this study, Lang’s model is applied to movement images of lifting of 4.5 and 9 kg weights. Twenty-two male and 17 female students participated in the study. During the imaginary lifting of the weights, the electromyographical activity (EMG) of both biceps brachii muscles were assessed. Imagery ability was measured with the Movement Imagery Questionnaire (MIQ) and another self-report rating scale. When response propositions were emphasized in the script, imaginary weight lifting resulted in greater muscle activity than when stimulus propositions were emphasized. During imagined lifting, EMG activity of the active arm was greater than that of the passive arm. In addition, in the active arm, a significant difference in EMG activity was found between 9 kg and 4.5 kg. It was concluded that Lang’s model is also applicable to emotionally neutral movement Imagery.

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.

The effects of anxiety on perceiving the reachability of passing objects

Abstract Three groups of 12 observers (a high trait anxiety group, a neutral trait anxiety group, and a low trait anxiety group) judged whether approaching balls were reachable or not under two conditions: a control condition and an anxiety condition. Under the anxiety condition, an egostressor was used to provoke anxiety on the part of the observers. State anxiety, as measured by the state scale of the State-Trait Anxiety Inventory (STAI; Spielberger, Gorsuch, & Lushene, 1970) and the anxiety thermometer, was found to increase significantly for the high trait anxiety group only. Heart rate elevation above resting level however was found to remain high under the anxiety condition and to decrease as the experiment progressed under the control condition for all three groups, suggesting that they were all affected by the anxiety manipulation. In line with the predictions of the theory of affordances, anxiety did not influence the location of the judged critical point. The steepness of the slope of the discri...

The role of anxiety in perceiving and realizing affordances

Three experiments were conducted to examine the role of anxiety in perceiving and realizing affordances in wall climbing. Identical traverses were situated high and low on a climbing wall to manipulate anxiety. In Experiment 1, participants judged their maximal overhead reachability and performed maximal reaches on the climbing wall. Anxiety was found to reduce both perceived and actual maximal reaching height. In Experiment 2, participants climbed from right to left and back again on the high and low traverses, which now entailed an abundance of holds. Consistent with the reduction of perceived and actual maximal reaching height found in Experiment 1, anxiety led to the use of more holds. Finally, in Experiment 3, points of light were sequentially projected around the participants while they were climbing to measure attention. As participants detected fewer lights in the high-anxiety condition, it was concluded that anxiety narrowed attention. In general, the results underscored that the actors emotional state plays an important role in perceiving and realizing affordances and that the perception of affordances changes as the accompanying action capabilities change.

Shedding Some Light on Catching in the Dark: Perceptual Mechanisms for Catching Fly Balls

To catch a lofted ball, a catcher must pick up information that guides locomotion to where the ball will land. The acceleration of tangent of the elevation angle of the ball (AT) has received empirical support as a possible source of this information. Little, however, has been said about how the information is detected. Do catchers fixate on a stationary point, or do they track the ball with their gaze? Experiment 1 revealed that catchers use eye and head movements to track the ball. This means that if AT is picked up retinally, it must be done by means of background motion. Alternatively, AT could be picked up by extraretinal mechanisms, such as the vestibular and proprioceptive systems. In Experiment 2, catchers reliably ran to intercept luminous fly balls in the dark, that is, in absence of a visual background, under both binocular and monocular viewing conditions. This indicates that the optical information is not detected by a retinal mechanism alone.

INDIVIDUAL DIFFERENCES IN REACTIVITY TO AND COPING WITH THE STRESS OF LECTURING

The aim of this study was to evaluate the moderating effect of several psychologically and biologically defined characteristics for both psychological and physiological indices of reactivity to and coping with lecturing stress. Student teachers were measured in two standardized lecturing situations: once at the start of a three-month practice period and once at the end of this period. Reactivity was operationalized as an increase in heart rate, cortisol excretion and subjective anxiety responses in anticipation of and at the start of the lecture. Coping was operationalized as the attunement of these responses during, or recovery after lecturing (short term coping), and as the adaptation of these responses across the three-month practice period (long term coping). It was found that reactivity to and (particularly long term) coping with the lecturing stressor could well be predicted by moderators such as physical fitness, extraversion, neuroticism, social anxiety and several coping styles. Specificity of predictor sets for sex and response parameters is discussed.

Thoughts and attention of athletes under pressure: skill-focus or performance worries?

Abstract Choking under pressure in sport has been explained by either explicit attention to skill execution (self-focus theories), or attention to performance worries (distraction theories). The aim of the present study was to find out which focus of attention occurs most often when expert athletes perform under pressure. Two retrospective methods were employed, namely, verbal reports and concept mapping. In the verbal reports, 70 expert athletes indicated their main focus of attention when performing under high pressure in competition. For concept mapping seven expert athletes generated statements about their focus of attention in such high-pressure situations. These statements were clustered and rated on how often they occurred and how important they were for choking. Both methods revealed that under pressure attention of expert athletes was often focused on worries and hardly ever on movement execution. Furthermore, the athletes reported that they focused attention on external factors and that they reverted to positive monitoring in an attempt to maintain performance. These results are more in line with distraction theories than self-focus theories, suggesting that attention to performance worries rather than to skill execution generally explains choking.