We investigated age-related differences in finger coordination during rotational hand actions. Two hypotheses based on earlier studies were tested: higher safety margins and lower synergy indices were expected in the elderly. Young and elderly subjects held a handle instrumented with five six-component force sensors and performed discrete accurate pronation and supination movements. The weight of the system was counterbalanced with another load. Indices of synergies stabilizing salient performance variables, such as total normal force, total tangential force, moments produced by these forces, and total moment of force were computed at two levels of a hypothetical control hierarchy, at the virtual finger-thumb level and at the individual finger level. At each level, synergy indices reflected the normalized difference between the sum of the variances of elemental variables and variance of their combined output, both computed at comparable phases over repetitive trials. The elderly group performed the task slower and showed lower safety margins for the thumb during the rotation phase. Overall, the synergy indices were not lower in the elderly group. In several cases, these indices were significantly higher in the elderly than in the younger participants. Hence, both main hypotheses have been falsified. We interpret the unexpectedly low safety margins in the elderly as resulting from several factors such as increased force variability, impaired feed-forward control, and the fact that there was no danger of dropping the object. Our results suggest that in some natural tasks, such as the one used in this study, healthy elderly persons show no impairment, as compared to younger persons, in their ability to organize digits into synergies stabilizing salient performance variables. 相似文献
We propose a person-centered framework for conceptualizing subjective careers in an increasingly boundaryless work context. Specifically, we argue that entrepreneurship, professionalism, and leadership (EPL) can serve as three key dimensions of subjective career space. We relate this framework to earlier macro-level national and organizational career models proposed by Kanter (1989) and Schein (1978). Our empirical study involving 10,326 Singaporean university students demonstrated that entrepreneurial, professional, and leadership career aspirations (including motivations, efficacies, and intentions) can be measured independently, that these career dimensions are independent of vocational interests, and that they are to some degree viewed as competing career alternatives. We also show that EPL motivation profiles can operationalize the boundaryless and protean career concepts. Individuals concurrently high in entrepreneurial, professional, and leadership career motivations, and those high in entrepreneurial and leadership motivations are highest in boundaryless and self-directed career attitudes, while those primarily motivated for professional careers hold the most traditional career attitudes. We conclude by discussing the potential of the framework for understanding human resource issues at organizational and national levels and for enhancing the study of entrepreneurship, professionalism, and leadership. 相似文献
Semantic processing from parafoveal words is an elusive phenomenon in alphabetic languages, but it has been demonstrated only for a restricted set of noncompound Chinese characters. Using the gaze-contingent boundary paradigm, this experiment examined whether parafoveal lexical and sublexical semantic information was extracted from compound preview characters. Results generalized parafoveal semantic processing to this representative set of Chinese characters and extended the parafoveal processing to radical (sublexical) level semantic information extraction. Implications for notions of parafoveal information extraction during Chinese reading are discussed. 相似文献
Sex Roles - We introduce a new inventory measuring sex-based harassment intentions and threat perceptions grounded in gender status threat theories (Berdahl, 2007; Stephan et al., 2016). In Study 1... 相似文献
Parent–adolescent relationships play an important role in protecting adolescents from depressive symptoms. However, there are no consistent conclusions about the extent to which fathers and mothers uniquely contribute to adolescents’ depressive symptoms. The present study aimed to acquire knowledge in this research area in two ways. First, this study separated the potential impacts of father–child and mother–child relationships on depressive symptoms in Chinese adolescents. Second, this study used a longitudinal design with nationally representative samples from the China Education Panel Survey. A total of 8794 middle school students in grade 7 completed measures of father–adolescent and mother–adolescent relationships, and depressive symptoms twice (T1 and T2; one-year interval). Results indicated that both positive father–adolescent and mother–adolescent relationships had negative effects on depressive symptoms in female adolescents. However, positive father-adolescent, not mother-adolescent, relationships had a negative effect on depressive symptoms in male adolescents. These findings suggest that positive parent–adolescent relationships could reduce early adolescents’ depressive symptoms, but positive father–adolescent and mother–adolescent relationships might have different protective effects on early adolescents’ depressive symptoms among male and female adolescents in China.
Teaching educational materials to others enhances the teacher's own learning of those to‐be‐taught materials, although the underlying mechanisms remain largely unknown. Here, we show that the learning‐by‐teaching benefit is possibly a retrieval benefit. Learners (a) solved arithmetic problems (i.e., they neither taught nor retrieved; control group), (b) taught without relying on teaching notes (i.e., they had to retrieve the materials while teaching; teaching group), (c) taught with teaching notes (i.e., they did not retrieve the materials while teaching; teaching without retrieval practice [TnRP] group), or (d) retrieved (i.e., they did not teach but only practised retrieving; retrieval practice group). In a final comprehension test 1 week later, learners in the teaching group, as did those in the retrieval practice group, outperformed learners in the TnRP and control groups. Retrieval practice possibly causes the learning benefits of teaching. 相似文献