An empirical validation of a dynamic systems model of interaction: do children of different sociometric statuses differ in their dyadic play?

Studying short-term dynamic processes and change mechanisms in interaction yields important knowledge that contributes to understanding long-term social development of children. In order to get a grip on this short-term dynamics of interaction processes, the authors made a dynamic systems model of dyadic interaction of children during one play session. The control parameters of the model relate to children's goal-directedness, concerns, emotional appraisals, social power, and social competence. Three groups of dyads of different sociometric statuses are represented by specific control parameter values. The model's order parameters consist of children's emotional expressions and other- versus self-directed actions. This article describes the empirical validation of the model and the methods needed for such validation. It focuses on the model's predictions of averages and distributions of the major variables, of the occurrence of attractors and power law distributions, and on the model's sensitivity. Overall, the model fits the empirical data well. In the discussion, we reflect on the developmental and methodological implications for explaining social interaction on the short-term as well as on the long-term time scale. In addition, implications for intervention and assessment are presented, in particular relating to the problem of rejection.     

Risk Regulation, EU Law and Emerging Technologies: Smother or Smooth?

Risk analysis as a regulatory driver has now become firmly entrenched in public health and environmental protection. Risk analysis at any level essentially has to accommodate two gut feelings of the constituency: whether society should be risk-prone or risk averse, and whether government and its institutions can be trusted to make the necessary decisions with a high or a low degree of discretion. The precautionary principle (or rejection thereof) arguably is the ultimate reflection of the promotion of risk to a societal value. There is no doubt that especially amongst the representatives of the Member States (as opposed to the officials at the European Commission), public (pre)caution with respect to the long-term environmental and public health implications of gene technology influenced the reluctance to allow marketing of GM foods and feeds until a strict regulatory regime had been rolled out. Industry would argue that the delay in regulation, as well as the eventual regime was of such a nature as to stifle the technology. This contribution reviews a number of features of standard EU risk analysis decisions, so as to assess its current propensity towards smothering rather than smoothing the introduction of new technology. The current development of a regulatory framework for nanotechnology serves as a case study.

The development and learning of the visual control of movement: An ecological perspective

We compare development and learning of the visual control of movement from an ecological perspective. It is argued that although the constraints that are imposed upon development and learning are vastly different, both are best characterised as a change towards the use of more useful and specifying optic variables. Implicit learning, in which awareness is drawn away from movement execution, is most appropriate to accomplish this change in optic variable use, although its contribution in development is more contentious. Alternatively, learning can also be affected by explicit processes. We propose that explicit learning would typically invoke vision for perception processes instead of the designated vision for action processes. It is for that reason that after explicit learning performance is more easily compromised in the face of pressure or disorders. We present a way to deal with the issue of explicit learning during infancy.     

Anticipatory responses to perturbation of co-ordination in one-handed catching.

Anticipatory responses to perturbation have rarely been studied in the co-ordination of dynamic interceptive actions. In this study, the kinematics of ball catching were examined in skilled catchers when mechanical perturbation of the catching arm was expected and unexpected. During trials where the perturbation was anticipated, participants initiated movements earlier (207 +/- 32 ms) than in randomly perturbed trials (223 +/- 34 ms). Furthermore, several individuals also tended to move their hand faster when perturbations were expected compared to baseline trials. Individual analyses revealed that three out of eight participants exhibited changes in the relative timing of the grasp phase to adapt to the specific manipulation of task constraints. Anticipatory responses were revealed in changes not only at movement initiation but also in the resulting adaptations to the co-ordination of reach and grasp phases of ball catching. When the catchers could not anticipate perturbations, movement strategies suggested the use of a continuous tracking-based mode of control rather than a prediction-based mode of control.     

Rate of change of angular bearing as the relevant property in a horizontal interception task during locomotion

The authors ran 3 experiments to investigate how catchers deal with the horizontal component of the ball's trajectory in an interception task during locomotion. The experiments were built upon the finding that velocity adaptations are based upon changes in the horizontal angular position or velocity of the ball with respect to the observer (M. Lenoir, M. Janssens, E. Musch, E. Thiery, J. Uyttenhove, 1999) a potential underlying information source for that strategy is described. In Experiment 1, actor (N = 10 participants)and ball approached each other along the legs of a V-shaped track. When the velocity and the initial angular bearing of the ball were varied, the observed behavior fitted with nulling the horizontal angular velocity of the ball: A positive or negative angular velocity was compensated by a velocity change. Evidence was obtained that those adaptations are modulated by a critical change in, rather than by a critical state of, the environment-actor system. In Experiment 2, the distance between the head and an artificial end-effector was varied. Irrespective of that distance, participants (N = 7) accelerated and decelerated in order to keep the angular velocity of the ball with respect to the end-effector close to constant. The ecological relevance of that constant bearing angle strategy was confirmed in Experiment 3: Participants (N = 7) in that experiment freely ran to catch fly balls. The present results support the concept that one can explain with a limited number of control variables an actor's behavior in an interception task during self-motion.     

Exposure to physical movement in chronic back pain patients: no evidence for generalization across different movements

This study investigated whether the effects of exposure to one movement generalize towards another dissimilar movement in patients with low back pain. Thirty-nine patients (11 male, 28 female; mean age=43.49 yrs) were requested to perform two movements twice, i.e. bending forward and straight leg raising. During each of the four trials, baseline pain, expected pain and experienced pain were recorded. Analyses revealed that patients initially overpredicted pain, but after exposure the overprediction was readily corrected. This exposure effect did not generalize towards another dissimilar movement. The above pattern of results was only characteristic for patients reporting a high frequency of catastrophic thinking about pain. Low pain catastrophizers did not overpredict pain. The results are discussed in terms of the view that exposure may be better conceived of as the learning of exceptions to a general rule.     

The impact of spatiotemporal sampling on time-to-contact judgments

When motion in the frontoparallel plane is temporally sampled, it is often perceived to be slower than its continuous counterpart. This finding stands in contrast to humans' ability to extrapolate and anticipate constant-velocity motion. We investigated whether this sampling bias generalizes to motion in the sagittal plane (i.e., objects approaching the observer). We employed a paradigm in which observers judged the arrival time of an oncoming object. We found detrimental effects of time sampling on both perceived time to contact and time to passage. Observers systematically overestimated the time it would take a frontally approaching object to intersect their eye plane. To rule out artifacts inherent in computer simulation, we replicated the experiment, using real objects. The bias persisted and proved to be robust across a large range of temporal and spatial variations. Energy and pooling mechanisms are discussed in an attempt to understand the effect.     

Children's search for targets located within and beyond the field of view: effects of deafness and age

The localisation time of visual targets within and beyond the field of view and the relative timing of the onsets of eye and head movements were examined in deaf and hearing children of two age groups: 5-7 years and 10-12 years. Compared to their hearing peers, the deaf children showed more often a mode of eye-head coordination in which the head leads the eye. The discrepancy between the onsets of eye and head movements were greater for the younger than for the older groups. Furthermore, the deaf children took more time than the hearing children to localise the targets; especially the young deaf differed from their hearing contemporaries. These findings support the view that during development the differences in visual search between deaf and hearing children decrease. The results are discussed in the context of a distinction between representational and sensorimotor control of eye-head responses.     

Friendly fire: Longitudinal effects of exposure to violent video games on aggressive behavior in adolescent friendship dyads

Research on gaming effects has focused on adolescence, a developmental period in which peer relationships become increasingly salient. However, the impact of peers on the effects of violent gaming on adolescents has been understudied. This study examined whether adolescents’ exposure to violent video games predicted their own and their friend's aggression one year later. Among 705 gaming adolescents, 141 dyads were identified based on reciprocated best friend nominations (73.8% male, M_age = 13.98). Actor‐Partner Interdependence Models indicated that adolescent males’ (but not females’) exposure to violent games positively predicted the aggression of their best friend 1 year later. This effect appeared regardless of whether the friends played video games together or not. The study illustrates the importance of peers in the association between violent gaming and aggression.