Extracting Global and Local Dynamics From the Stochastics of Rhythmic Forearm Movements

The authors examined the dynamics governing rhythmic forearm movements that 9 participants performed under a variety of task constraints by using a generic, unbiased analysis technique for extracting the drift coefficients of Fokker-Planck equations from stochastic data. From those coefficients, they reconstructed and analyzed vector fields and phase portraits to identify characteristic, task-dependent kinematic and dynamical features. They first directly estimated the parameters of weakly nonlinear self-sustaining oscillators from the extracted drift coefficients. The estimated parameters that the authors had selected instinctively and then particularized by using averaging methods largely confirmed previously derived limit-cycle models. Next, they ventured beyond limit-cycle models to examine global and local dynamical features that those models cannot adequately address, particularly task-dependent changes in flow strength and curvature and distinct dynamical features associated with flexion and extension. The authors argue that those features should be focal points of researchers' future modeling efforts to formulate a more adequate and encompassing account of the dynamics of rhythmic movement.     

A Dynamical Systems Approach to Manual Tracking Performance

Manual tracking performance was investigated from the perspective of dynamical systems theory. The authors manipulated the type of visual display, the control system dynamics, and the frequency of the sinusoidal input signal to examine couplings with various phases between the visual signal and control movements. Analyses of the system output amplitude ratio and relative phase showed that participants (N = 24) performed poorly with 90° relative phase coupling. All the couplings became less stable as the movement frequency increased. The authors developed an adaptive oscillator model with linear damping to describe the coupled system consisting of the human performer, the visual display, and the control system dynamics. A geometric account of the stability of performance at different relative phases is also presented.     

Beyond Curve Fitting to Inferences About Learning

In this commentary, the authors elaborate on the issue of going beyond curve fitting to the drawing of inferences about motor learning. They argue that the agenda of A. Heathcote and S. Brown (2004) is largely a theory-free, curve-fitting enterprise that can be useful for certain aspects of describing behavior change, but that its gold standard of percentage of variance accounted for can also be misleading in its relevance to the theory of learning. Clearly, analysis methods are necessary and some are better than others, but the researcher can more fully exploit the relevance of methods to the construct with a priori theorizing than with a data-driven strategy of maximizing percentage of variance accounted for in curve fitting.     

The older,the wider: On-field tactical behavior of elite-standard youth soccer players in small-sided games

PurposeYoung soccer players need excellent tactical skills to reach the top. Tactical behavior emerges through interactions between opposing teams. However, few studies have focused on on-field tactical behavior of teams with talented soccer players. Therefore, this study aimed to determine teams’ tactical behavior during small-sided games in two age categories, Under-17 and Under-19.MethodsPositional data of thirty-nine elite-standard soccer players were collected during twenty-four small-sided games to calculate longitudinal and lateral inter-team distances, stretch indices and length per width ratios. Corresponding interaction patterns and game-to-game variability were also determined.ResultsUnder-19 showed a significantly larger lateral stretch index and a significantly lower length per width ratio compared with Under-17. Furthermore, teams of both age groups showed similar large proportions of in-phase behavior. Variability of tactical performance measures within and between games was similar for Under-17 and Under-19.ConclusionsVariability within games seems to be functional for attacking teams for creating goal-scoring opportunities. In conclusion, the main difference was that Under-19 adopted a wider pitch dispersion than Under-17, represented by a larger lateral stretch index and smaller length per width ratio. Coach instructions and training exercises should be directed at exploiting pitch width to increase the pursuit of goal-scoring.     

The paradox between the numerically competent baby and the slow learning of two- to four-year-old children / La paradoja entre el bebé numéricamente competente y el lento aprendizaje de los niños de dos a cuatro años de edad

Abstract

Since the 1980s, numerous laboratory investigations have been arguing that infants are numerically competent. This work presents a critical review of this line of research. We propose that despite the repertoire of numerical abilities attributed to infants and the seemingly natural character of the very first numbers in the numerical series, the semiotic complexity of their use and comprehension poses a cognitive challenge that children undertake, motivated, supported and often guided by others. This challenge involves a high degree of semiotic organization of the material world as well as an ability to manage early sign systems, systems which children learn how to use during their first years of life and which form the platform on which numbers are based.     

Dislocation formation in the partially coherent interfaces of an embedded layer in a semi-infinite matrix

The formation of two misfit edge dislocations is theoretically investigated in the interfaces of a layer embedded in a semi-infinite matrix. Assuming the matrix–layer interfaces are partially coherent, the energy variation resulting from the formation of the dislocations from the lateral free surface of the structure has been determined in the shearing stress field due to the partial misfit. The mechanical stability of the structure is analysed with respect to the dislocation formation as a function of the size of the coherent region of the interface and the misfit strain.     

Cross-generational acceptance of and interest in advanced vehicle technologies: A nationwide survey

The number of older drivers on the roadways is increasing; at the same time, technology in the automotive environment is rapidly evolving. To investigate the potential impact of these converging changes, this study used a cross-generational approach to compare driver attitudes toward advanced automotive technologies. Approximately 1000 drivers between the ages of 18 and 85 located across the United States responded to a survey about their opinions regarding general technology, advanced in-vehicle technology, and near-horizon connected vehicle systems. Participant responses were categorized using a generational construct, sorting responses not only by age but by shared life experiences (e.g. economic circumstances, involvement in wartime activities, cultural movements, etc.). The oldest generation (the “Silent” generation) exhibited the least interest in and comfort with advanced technology, although they owned and used advanced in-vehicle technology at approximately the same rates as the two middle generations. The youngest generation (the “Millennial” generation) was most likely to be interested in and comfortable with technology, but was least likely to own vehicles with advanced technology. All participants expressed interest in safety-related connected vehicle systems, but less so in infotainment applications. Reservations regarding data security and system cost were shared across generations. These findings are framed in the context of an aging population with unique driving and vehicle needs, and provide information that may assist both with vehicle technology design aspects and the proposed large-scale implementation of connected vehicle systems, including considerations for seniors and emphasis on safety systems and data security.     

How do supporters perceive positive and negative psychological momentum changes during a simulated cycling competition?

ObjectiveThe present study examined changes in sport supporters' psychological momentum (PM) during a simulated cycling competition through the lens of the dynamical systems approach.DesignParticipants were asked to support one of two competing cyclists involved in a race that was displayed on a screen in a lecture hall.MethodThe race scenario was manipulated so that the image of the supported cyclist underwent either positive or negative momentum. At regular intervals, participants indicated their PM perceptions during the race.ResultsPM perceptions rapidly changed at the onset of both the positive and negative momentum sequences and then remained stable, reflecting negative hysteresis. Supporters tended to anticipate the future performance of a given athlete on the basis of their current performance. Moreover, this anticipatory tendency was stronger during the positive momentum sequence than during the negative momentum sequence.ConclusionThese results provide initial insights into how PM perceptions of sport supporters change during a competition.     

Linking the Levels: Network and Relational Perspectives for Community Psychology

In this article, we assert that relationships and networks are of paramount importance for understanding and improving settings, neighborhoods, communities, and larger social systems. Despite previous acknowledgements of their relevance, relational and social network perspectives and analyses remain underrepresented in community psychological research and action. Here, we claim that network and relational perspectives can provide conceptual and empirical ‘links’ between levels of analysis, more fully reflecting a transactional view. We also describe some of the sophisticated methodologies that can be employed in empirical studies drawing on these perspectives. Additionally, we contend that core concepts in community psychology such as health promotion, empowerment, coalition building, and dissemination and implementation can be better understood when employing relational and network perspectives. As an introduction to this special issue of American Journal of Community Psychology, we draw out themes and key points from the articles in the issue, and offer recommendations for future advancement of these perspectives in the field.