On-line trajectory modifications of planar,goal-directed arm movements

Sometimes a goal-directed arm movement has to be modified en route due to an unforeseen perturbation such as a target displacement or a hand displacement by an external force. In this paper several aspects of that modification process are addressed. Subjects had to perform a point-to-point movement task on a computer screen using a mouse-coupled pointer as the representation of the hand position. Trajectory modifications were imposed by unexpectedly changing the position of the target or by changing the relation between mouse and screen pointer.In the first series of experiments, we examined how often a trajectory is updated. Here, trajectory modifications were imposed by unexpectedly changing the normal relation between mouse and pointer to a shear-like relation, where a percentage of the forward/backward position of the hand was added to the pointer position in the left/right direction. Withdrawal of visual feedback during the movement revealed that trajectories were updated at interval times shorter than 200 ms. From the similarity with experiments where the original relation between mouse and pointer was restored during the movements, we conclude that motor plans are updated on-line to move the hand from its current perceived position to the target.In a second series of experiments, we studied whether a continuous change in target position yields similar trajectory modifications as a continuous hand displacement. To mimic the latter perturbation, we used the above-mentioned distortion of the mouse-pointer relation. We found that the resulting hand paths did not differ for the two visual perturbations and conclude that the perturbed, goal-directed movements are modified in a consistent way, irrespective of whether the position of the target or hand was perturbed. Simulations of the experimental data with a kinematic reaching model support this conclusion.     

Coping with an ego-threat: Monitoring and blunting during an intelligence test

This study investigated the predictive validity of the Miller Behavioral Style Scale (MBSS; Miller, 1987). Subjects had to work on an intelligence test. During this test, they could observe lights that informed them on how they were performing. There were two conditions: a low-stress condition (n = 37) in which the lights always indicated that the subject was performing well, and a high-stress condition (n.= 33) in which the lights signalled a deterioration of performance. In general, little support was found for the predictive validity of the MBSS.     

Complexity of health care needs and interactions in multidisciplinary medical teams

By using an information processing and social identity approach, this study examines the relationships between the complexity of the health care needs of a patient and (1) the interactions among physicians during team meetings and (2) how the meeting participants evaluate the discussion. Three dimensions of the complexity of the health care needs are related to the interactive behaviour of medical specialists during meetings of multidisciplinary medical teams. Three medical teams from a Dutch university hospital, each discussing a total of 40 patients, were observed. The results show that component complexity was positively related to the amount of information team members exchanged, to positive reactions, and to the positive evaluation of the discussion. Two other dimensions (interrelatedness of needs and ambiguity) have to be considered in concert: interrelatedness was positively related to negative reactions but only if ambiguity was low; and, further, ambiguity was positively related to evaluative behaviour and to positive reactions, and negatively to the evaluation of the discussion, but only if interrelatedness was low.     

An additive factors analysis of the effect(s) of location cues associated with auditory stimuli on stages of information processing

The additive factors method (AFM) was used as a tool for assessing the locus (or loci) of the detrimental effect of auditory location cues in the chain of (visual) information processing. In the first experiment the location variable was factorially combined with response specificity, which is assumed to affect the response adjustment stage. A second experiment was performed in which movement amplitude, assumed to affect the response programming stage, was manipulated in addition to the location variable and a different variety of response specificity. Finally, the location variable was combined with relative S-R frequency, which is also assumed to affect the response programming stage, in a third experiment. The results of these experiments showed additive effects of the location variable with motor variables. The remaining two experiments were designed to assess the effects of location cues on response selection. In these experiments the location variable was combined with the number of response alternatives. Response speed decreased with an increase in the number of response alternatives. However, the effects of the location variable and number of response alternatives were additive. According to the additive factor logic, then, the results of experiments 1, 2 and 3 seem to indicate that the locus of interference of the location cues is not in the later response stages of the reaction process. The results of the last two experiments were interpreted to suggest that the effects of location cues and the number of response alternatives affect either different processes within the response selection stage or affect different process stages. It was concluded that the latter alternative explains most of the data currently available and that the stimulus identification stage is the most likely candidate for the locus of the location effect.     

God changes people: modes of authentication in Evangelical conversion narratives

One of the distinguishing characteristics of Evangelicalism is the conversion story. In this article we focus on the conversion stories of interviewees within the setting of several related Evangelical television programs broadcast in the Netherlands since the 1980s. We argue that the conversion story is construed through a particular view on and practice of authenticity. Thus we see that, in the televised conversion story, modes of authentication are at work in what we analytically distinguish as frames, narratives, and strategies of authentication. We argue that the idea of an authentic transformation has changed from a more fundamentalist mode of authentication, emphasizing the subjection of the self to a particular religious narrative, to a more expressive mode of authentication that emphasizes the exploration of the inner, unique self of the interviewee.     

Left hemispheric preference and alexithymia: A neuropsychological investigation

Starting from the hypothesis that alexithymics show a hyperactive left hemisphere, this study investigated the neural processing of visual information in two alexi-thymic groups and one nonalexithymic group. The subjects performed a lateralised visual-matching task, through which the proportions of ipsilateral and contralateral processing of three types of stimuli were assessed. In line with the hypothesis it was demonstrated that, in contradistinction to nonalexithymics, the two groups of alexithymics showed a left hemispheric preference in their neural processing of emotion words.