Attentional focus effects in balance acrobats

Performing and learning motor skills has been shown to be enhanced if the performer adopts an external relative to internal focus (or no focus) of attention (Wulf 2007). The present study examined the generalizability of this effect to top-level performers (balance acrobats). Participants performed a balance task (standing on an inflated rubber dish) under each of three attentional focus conditions: (a) external focus (i.e., minimize movements of the disk), (b) internal focus (i.e., minimize movements of the feet), and (c) control conditions (no focus instructions). While there were no differences between conditions in the amount of postural sway, the frequency of movement adjustments was higher in the control condition, relative to both external and internal focus conditions. This suggests that movement automaticity and postural stability were greatest when the balance experts were free to adopt their "normal" focus of attention. The finding implies that there may be a limit to the performance-enhancing effects of external focus instructions for top-level performers. The findings are discussed in terms of action control levels and possible changes in the optimal attentional focus with the performer's level of expertise.     

R&D drivers and age: Are young firms different?

This study examines the relationship between R&D drivers and firm's age, taking into account the autoregressive nature of innovation.     

Is dealing with errors in the classroom specific for school subjects? A study of the error climate in mathematics,German, and English

A frequent observation in the school context is that opportunities to learn from errors are often missed. However, a positive error climate may support learning from errors. For the school subject of mathematics, some findings about characteristics of the error climate already exist. But, a comparison of the error climate between different school subjects is still pending. In the present study, it is analyzed whether the error climate differs in different school subjects and whether the same interrelations between the ways in which individuals deal with errors can be found in these different school subjects. In a study with 937 students from 48 classrooms from grades 5 to 7, in different secondary schools in Germany and Austria, we assessed the error climate and individual reactions following errors in mathematics, German, and English. Small mean differences between mathematics and the two language subjects were yielded. In addition, we found medium-sized correlations between the error climate measures in the three school subjects. However, the same pattern of interrelations between error climate and the way individuals deal with errors for all three school subjects could be shown. The results suggest that the perception of the error climate is rather similar in different school subjects. This has implications, for instance, for interventions that aim at fostering the error climate.

     

Trajectory tracking for a quadrotor under wind perturbations: sliding mode control with state-dependent gains

The problem of position tracking of a mini drone subject to wind perturbations is investigated. The solution is based on a detailed unmanned aerial vehicle (UAV) model, with aerodynamic coefficients and external disturbance components, which is introduced in order to better represent the impact of the wind field. Then, upper bounds of wind-induced disturbances are characterized, which allow a sliding mode control (SMC) technique to be applied with guaranteed convergence properties. The peculiarity of the considered case is that the disturbance upper bounds depend on the control amplitude itself (i.e. the system is nonlinear in control), which leads to a new procedure for the control tuning presented in the paper. The last part of the paper is dedicated to the analysis and reduction of chattering effects, as well as investigation of rotor dynamics issues. Conventional SMC with constant gains, proposed first order SMC, and proposed quasi-continuous SMC are compared. Nonlinear UAV simulator, validated through in-door experiments, is used to demonstrate the effectiveness of the proposed controls.     

Kieferchirurgische Operationsplanung mit Hilfe von Techniken der virtuellen Realit?t

Zusammenfassung.   Für ein vollst?ndig computergestütztes Planungssystem zum Zwecke der kieferchirurgischen Operationsplanung ist die Bereitstellung von virtuellen Werkzeugen für den Chirurgen eine grundlegende Voraussetzung. Ausgehend von den Volumendaten mit Sch?del- und Kieferknochen des Patienten erm?glicht ein einfaches Interface unter Verwendung einer geeigneten Visualisierung und haptischer Eingabeger?te die interaktive Definition und Manipulation einzelner virtueller Knochensegmente. Wir haben moderne kraftrückgekoppelte Ger?te aus dem Niedrigpreisbereich eingebunden und auf ihre F?higkeit untersucht, das dreidimensionale Verst?ndnis im Planungsproze?durch Anlehnung an die Vorg?nge bei der chirurgischen Prozedur zu erh?hen. Durch diese Eingabeger?te ist es m?glich, die Knochensegmentierung für eine Osteotomie des Unterkiefers intuitiver und schneller durchzuführen. Die definierten Teilvolumina ergeben zusammen mit ihrer r?umlichen Neuanordnung auf Grundlage einer kephalometrischen Analyse einen Operationsplan. Nach erfolgter Planung werden die Planungsergebnisse in den Operationssaal übertragen. Die intraoperativen Techniken beinhalten die Visualisierung der Planungsergebnisse, die Steuerung der Anwendung über Sprache und die Bestimmung der Patientenposition mittels eines elektromagnetischen 3D-Trackingsystems. Eingegangen am 27. April 2000 / Angenommen am 21. Februar 2001     

The effects of teaching mental calculation in the development of mathematical abilities

Many countries include mental calculation within their curriculum, as the literature shows benefits related to it. However, evidence mainly focuses on the effects of teaching mental calculation on computational fluency. Therefore, the authors aimed to assess the effects of teaching mental calculation on double-digit computation, number line estimation, and computational fluency. Fifty second-grade students from a Uruguayan private school were randomly assigned to a control or treatment condition (n?=?25 each). The treatment group participated in 15 sessions of mental calculation intervention, while the control group received “teaching as usual.” Assessment took place before and after the intervention. The authors found no significant impact of the treatment on the mathematical outcome variables. The results are explained in the context of the available literature and the methodological decisions taken. From a perspective of evidence-based teaching practices, the present study contributes to a better understanding of effective instructional principles.     

The Scientific Value of Cognitive Load Theory: A Research Agenda Based on the Structuralist View of Theories

In this paper, two methodological perspectives are used to elaborate on the value of cognitive load theory (CLT) as a scientific theory. According to the more traditional critical rationalism of Karl Popper, CLT cannot be considered a scientific theory because some of its fundamental assumptions cannot be tested empirically and are thus not falsifiable. According to the structuralist view of theories introduced by Joseph D. Sneed, a theory may be considered scientific even if it comprises nontestable fundamental assumptions. Rather, the scientific value of a theory results from the holistic empirical content of the overall theory net built around fundamental assumptions and from the successful applications of this theory net to explain and predict empirical findings. This latter view is helpful to explicate some implicit methodological assumptions of CLT research and to avoid the potential circularity of CLT’s fundamental assumptions. Additionally, the structuralist view of theories can be directly used to derive a research agenda for the future development of CLT.