Stiffness as a control variable in motor performance

In the experiments described in this article we investigated the control of stiffness of the effector system in relation to parameters of the movement. If the velocity of a movement is chosen, it appears that at the same time the stiffness of the effector system is set to a preferred value. By changing the instruction given to the subject it is possible to change the relationship between velocity and stiffness without changing the kinematic parameters of the movement.Finally, the changes of stiffness and velocity in a learning process are studied. In conformity with what might be expected on intuitive grounds, it is found that velocity increases spontaneously during learning while stiffness decreases. The results are discussed in connection with the generation of motor programmes.     

Grasp-Based Functional Coupling Between Reach- and Grasp-Related Components of Forelimb Muscle Activity

How are appropriate combinations of forelimb muscles selected during reach-to-grasp movements in the presence of neuromotor redundancy and important task-related constraints? The authors tested whether grasp type or target location preferentially influence the selection and synergistic coupling between forelimb muscles during reach-to-grasp movements. Factor analysis applied to 14–20 forelimb electromyograms recorded from monkeys performing reach-to-grasp tasks revealed 4–6 muscle components that showed transport/preshape- or grasp-related features. Weighting coefficients of transport/preshape-related components demonstrated strongest similarities for reaches that shared the same grasp type rather than the same target location. Scaling coefficients of transport/preshape- and grasp-related components showed invariant temporal coupling. Thus, grasp type influenced strongly both transport/preshape- and grasp-related muscle components, giving rise to grasp-based functional coupling between forelimb muscles.     

Facing a Disruptive Face: Embodiment in the Everyday Experiences of “Disfigured” Individuals

In recent years, facial difference is increasingly on the public and academic agenda. This is evidenced by the growing public presence of individuals with an atypical face, and the simultaneous emergence of research investigating the issues associated with facial variance. The scholarship on facial difference approaches this topic either through a medical and rehabilitation perspective, or a psycho-social one. However, having a different face also encompasses an embodied dimension. In this paper, we explore this embodied dimension by interpreting the stories of individuals with facial limb absence against the background of phenomenological theories of the body, illness and disability. Our findings suggest that the atypical face disrupts these individuals’ engagement with everyday projects when it gives rise to disruptive perceptions, sensations, and observations. The face then ceases to be the absent background to perception, and becomes foregrounded in awareness. The disruptions evoked by facial difference call for adjustments: as they come to terms with their altered face, the participants in our study gradually develop various new bodily habits that re-establish their face’s absence, or relate to its disruptive presence. It is through these emergent habits that facial difference comes to be embodied. By analyzing the everyday experiences of individuals with facial limb absence, this article provides a much-needed exploration of the embodied aspects of facial difference. It also exemplifies how a phenomenological account of illness and disability can do justice both to the impairments and appearance issues associated with atypical embodiment.     

The Influence of Control on Belief in Conspiracy Theories: Conceptual and Applied Extensions

Threats to control have been found to increase belief in conspiracy theories. We argue, however, that previous research observing this effect was limited in two ways. First, previous research did not exclude the possibility that affirming control might reduce conspiracy beliefs. Second, because of artificial lab procedures, previous findings provide little information about the external validity of the control threat–conspiracy belief relationship. In Study 1, we address the first limitation and find that affirming control indeed reduces belief in conspiracy theories as compared with a neutral baseline condition. In Study 2, we address the second limitation of the literature. In a large‐scale US sample, we find that a societal threat to control, that citizens actually experienced, predicts belief in a range of common conspiracy theories. Taken together, these findings increase insight in the fundamental relationship between the human need for control and the tendency to believe in conspiracy theories. Copyright © 2015 John Wiley & Sons, Ltd.     

Motivated information processing and group decision-making: Effects of process accountability on information processing and decision quality

Integrating dual-process models [Chaiken, S., & Trope, Y. (Eds.). (1999). Dual-process theories in social psychology. NewYork: Guilford Press] with work on information sharing and group decision-making [Stasser, G., & Titus, W. (1985). Pooling of unshared information in group decision making: biased information sampling during discussion. Journal of Personality and Social Psychology, 48, 1467-1478.], we predicted that groups with high epistemic motivation engage in more information-driven and less preference-driven interaction, and achieve better decisions. An experiment manipulating process accountability showed that groups under process accountability experienced greater need for more information, repeated unshared information more often, and more often chose the correct decision alternative. Mediation analysis established that epistemic motivation produced high quality decisions because it stimulated systematic information processing. Results also revealed that preference heterogeneity stimulated information-driven interaction and led to higher decision quality.     

A clinician survey of speech and non-speech characteristics of neurogenic stuttering

This study presents survey data on 58 Dutch-speaking patients with neurogenic stuttering following various neurological injuries. Stroke was the most prevalent cause of stuttering in our patients, followed by traumatic brain injury, neurodegenerative diseases, and other causes. Speech and non-speech characteristics were analyzed separately for these four etiology groups. Results suggested possible group differences, including site of lesion and influence of speech conditions on stuttering. Other characteristics, such as within-word localization of disfluencies and presence of secondary behaviors were comparable across the etiology groups. The implications of our results for the diagnosis of neurogenic stuttering will be discussed.

Educational objectives: After reading this article, the reader will be able to: (1) provide a concise overview of the main literature on neurogenic stuttering; (2) discuss the speech and non-speech characteristics of neurogenic stuttering; (3) provide an overview of current clinical practices for intervention with neurogenic stuttering patients and their perceived outcome.     

Switching between tasks and responses: a developmental study

Task switching requires the ability to flexibly switch between task rules and responses, and is sensitive to developmental change. We tested the hypothesis that developmental changes in task switch performance are associated with changes in the facilitating or interfering effect of the previously retrieved stimulus-response (S-R) association. Three age groups (7-8-year-olds, 10-12-year-olds and 20-25-year-olds) performed a two-choice reaction time (RT) task in which spatially compatible or incompatible responses were required. The RT costs associated with switching between tasks were larger when responses were repeated than when responses were alternated. Younger children showed a greater cost than adults when switching between tasks but repeating responses. This age difference decreased when the interval between the previous response and the upcoming stimulus increased. Switch costs were larger when switching to the compatible task than to the incompatible task, but this effect did not differ between age groups. These findings suggest that young children build up stronger transient associations between task sets and response sets, which interfere with their ability to switch to currently intended actions. A similar pattern has previously been observed for older adults (Mayr, 2001), suggesting a common contributor to task switching deficits across the life span.     

Short-term memory after all: comment on Sederberg, Howard, and Kahana (2008)

P. B. Sederberg, M. W. Howard, and M. J. Kahana have proposed an updated version of the temporal-context model (TCM-A). In doing so, they accepted the challenge of developing a single-store model to account for the dissociations between short- and long-term recency effects that were reviewed by E. J. Davelaar, Y. Goshen-Gottstein, A. Ashkenazi, H. J. Haarmann, and M. Usher (2005). In this commentary, the authors argue that the success of TCM-A in addressing the dissociations is dependent not only on an episodic encoding matrix but--critically--also on its implicit use of a short-term memory store--albeit exponential rather than buffer-like. The authors also highlight some difficulties of TCM-A in accounting for these dissociations, and they argue that TCM-A fails to account for critical data--the presentation-rate effect--that dissociates exponential and buffer-like models.     

Development and validation of a Dutch translation of the Big Five Inventory (BFI)

In this article, we describe the translation and validation of the Dutch Big Five Inventory (BFI; John & Srivastava, 1999), a short instrument designed to measure the Big Five factors of personality. We obtained evidence of the instrument's good psychometric properties in terms of factorial equivalence to the English original and other BFI translations and the relative independence and internal consistency of the five scales. The findings suggest that the instrument can be used in diverse age groups without substantial changes in factor structure. The Dutch BFI scales showed similar demographic correlates as the English original, with higher Agreeableness and Conscientiousness and lower Neuroticism values in older participants, higher Neuroticism values in women, and higher Openness and Conscientiousness values in better educated participants. Use of the Dutch BFI will allow researchers to integrate their findings with the extant Big Five research literature. The brevity of the instrument will be appealing to researchers who are concerned about taxing the time and motivation of their participants.