Chaos in Human Rhythmic Movement

Rhythmic movements typical of locomotory actions are usually modeled as limit cycle dynamics, and their deviations from pure periodicity are attributed to stochastic physiological noise. In the present study, the dynamics of human rhythmic movements were found to contain more than the 2 dynamically active variables expected from limit cycle dynamics; the number depended upon the size of the limb oscillator. Observed positive Lyapunov exponents and fractal attractor dimensions indicated that the gross variability of human rhythmic movements may stem largely from low-dimensional chaotic motion on strange attractors.     

An under-met and over-met expectations model of employee reactions to merit raises

The authors developed a model of how raise expectations influence the relationship between merit pay raises and employee reactions and tested it using a sample of hospital employees. Pay-for-performance (PFP) perceptions were consistently related to personal reactions (e.g., pay raise happiness, pay-level satisfaction, and turnover intentions). Merit pay raises were strongly related to reactions only among employees with high raise expectations and high PFP perceptions. The interactive effects of under-met/over-met expectations and PFP perceptions were mediated by the extent to which participants saw the raise as generous and they were happy with the raises they received. The authors discuss the implications of these findings for expectation-fulfillment theories, merit pay research, and the administration of incentives.     

Effects of explicit sway-minimization on postural--suprapostural dual-task performance

Participants performed a visual search task under immersive visualization conditions while standing in open or closed stance. In the combined instruction condition, participants were asked to minimize their sway while they performed the search task, and in the search-only condition, they were advised that sway was not of interest, and they were asked to focus their efforts on performing the search task. Regardless of instructions, participants swayed more and made more errors as search load increased. Participants also succeeded in reducing their sway when asked to do so. While search in closed stance tended to be faster than in open stance under search-only instructions, this pattern reversed significantly under combined instructions. We suggest that neither the facilitatory control hypothesis nor any resource-competition model of postural--suprapostural dual-tasking can fully account for the observed interplay of task-facilitation and task-interference effects. We offer adaptive resource-sharing as an alternative to these theories.     

Advantages of Rhythmic Movements at Resonance: Minimal Active Degrees of Freedom,Minimal Noise,and Maximal Predictability

Using time delay embedding, the authors applied phase space reconstruction to the time series of rhythmic movements of a hand-held pendulum. Subjects (N = 6) produced the manual oscillations about the wrist at the pendulum's resonant frequency and at a higher and a lower frequency. The number of active degrees of freedom required to capture the dynamics of the rhythmic behavior was 3 for the resonant frequency and 4 for each of the nonresonant frequencies. The residual high-dimensional noise was similarly lowest for the resonant frequency. Whereas 33% and 20%, respectively, of the vectors in the phase spaces of the dynamics higher and lower than resonance were unpredictable, only 12% were unpredictable at resonance. Finally, the predictability of the evolving dynamics extended farther into the future for oscillations at the resonant frequency. At resonance, the prediction horizon was 5 times farther than the prediction horizon for the higher than resonance behavior and 2.5 times farther than that for the lower than resonance behavior. The results suggest that, in pendular oscillations of a limb or limb segment, attunement of the central nervous system to the resonant frequency minimizes the variables to be controlled and maximizes the predictability of the rhythmic movement's chaotic dynamics.     

Cognitive functioning,personality variables and academic achievement of hemophilic and normal children: A comparative study

The present study was conceptualized in the context of the psychosocial needs of Hemophilic children and adolescents of Kolkata. Twenty four Hemophilic children and adolescents were compared with a matched group of normal controls to find out any specific difference in terms of visuomotor gestalt functioning, intellectual level, academic achievement and personality dimensions. Academic achievement was assessed by averaging the results of the last three consecutive school examinations. Intellectual functioning was assessed by Progressive Matrices by Raven, and personality dimensions were assessed by Junior Eysenck Personality Questionnaire. Chi square tests and ANOVA were conducted to determine whether the Hemophilic children differed significantly from the normal controls across age levels. Findings revealed that there was little difference between the two groups in terms of intellectual level, and most dimensions of personality, although the Hemophilics fared worse than normals in neuropsychological, social and academic aspects. Implication for intervention is discussed.     

Postural costs of suprapostural task load

In an immersive visualization experiment, participants performed a conjunction search task while standing either in open (heels 10 cm apart, feet at a comfortable angle) or closed stance (feet pressed together). In the world-frame condition, the search display maintained its position in space as the participant swayed, generating optic flow informative about sway. In the head-frame condition, the display maintained constant distance and orientation with respect to the participant's head, providing no visual information about sway. In both conditions, participants (surprisingly) searched faster while in the more difficult closed stance. Interpretation of this result is unclear. Participants also swayed more as search-load increased, and made more errors in the high search-load condition. It is suggested that this performance tradeoff is a result of the sharing of a limited-capacity, modality-non-specific spatial-attentional resource between postural and suprapostural tasks.     

A masked priming ERP study of letter processing using single letters and false fonts

Previous event-related potential (ERP) research on letter processing has suggested that a P150 reflects lowlevel, featural processing, whereas a P260 reflects high-level, abstract letter processing. In order to investigate the specificity of these effects, ERPs were recorded in a masked priming paradigm using matching and nonmatching pairs of letters (e.g., g-g, g-j) and false fonts (e.g.,      

Fatigue Impact Scale: Its validation in patients with chronic obstructive pulmonary disease

The aim of this study was to investigate the reliability and validity of the Fatigue Impact Scale (FIS) among patients with chronic obstructive pulmonary disease (COPD) and shorten the questionnaire. The empirically developed FIS, which comprised three subscales (cognitive, physical and psychosocial), was tested originally on Pipers' theoretical framework of subjective manifestations of fatigue, including behavioural, physical, emotional and cognitive expressions. The data analysed here consisted of responses from 296 patients with COPD who reported fatigue. The dimensionality of the FIS was examined using confirmatory factor analysis. A reduction of 15 items from the original FIS was made based on theory, modification indices and factor loadings. The results indicate that a nested-factor model with one general behavioural factor and three specific factors, physical, emotional and cognitive, shows acceptable fit. A modified version of 25 items, FIS-25 was developed. The original FIS and the FIS-25 were able to discriminate between patients with differing duration of fatigue. Test - retest correlations ranged from .70 to .85 for items and .94 for the total scale. Due to modification, the FIS-25 needs to be validated on a new group of patients with COPD.     

Teacher-Student Relations in Two Tibetan Buddhist Groups in Helsinki

Based on sixteen interviews with members of two Tibetan Buddhist groups in Helsinki, Finland, this article investigates how the role of the guru, power imbalance and power abuse are perceived by the students. This qualitative study aims at understanding what shape the reverence to the Vajrayana teacher takes in the egalitarian environment of a European country, where Buddhism is a relatively new phenomenon. The interviews show that while teachers are not losing importance, ways of choosing and paying respect to them changes. They also reveal confusion in defining abuse, and emphasis on personal agency and teachers’ accountability for avoiding it.