Assessment of model-based image-matching for future reconstruction of unhelmeted sport head impact kinematics

Player-to-player contact inherent in many unhelmeted sports means that head impacts are a frequent occurrence. Model-Based Image-Matching (MBIM) provides a technique for the assessment of three-dimensional linear and rotational motion patterns from multiple camera views of a head impact event, but the accuracy is unknown for this application. The goal of this study is to assess the accuracy of the MBIM method relative to reflective marker-based motion analysis data for estimating six degree of freedom head displacements and velocities in a staged pedestrian impact scenario at 40 km/h. Results showed RMS error was under 20 mm for all linear head displacements and 0.01–0.04 rad for head rotations. For velocities, the MBIM method yielded RMS errors between 0.42 and 1.29 m/s for head linear velocities and 3.53–5.38 rad/s for angular velocities. This method is thus beneficial as a tool to directly measure six degree of freedom head positional data from video of sporting head impacts, but velocity data is less reliable. MBIM data, combined in future with velocity/acceleration data from wearable sensors could be used to provide input conditions and evaluate the outputs of multibody and finite element head models for brain injury assessment of sporting head impacts.     

Building Bridges: Reflections on the problem of transfer of learning in mathematics

The takeup of opportunities for applying formal learning outside the school is often disappointing – to teachers, parents, employers, and many pupils. Not surprisingly, there is much controversy among researchers in mathematics education and related fields, as to the reasons. Here I argue that neither traditional nor constructivist views, with their simplistic faith in the basic continuity of knowledge across contexts, nor currently popular ‘insulationist’ views such as the strong form of situated cognition, which claims that transfer is basically not possible, are adequate. Instead, I analyse why transfer is problematical in principle, and undependable in practice. I recommend an alternative approach for building bridges between practices, based on analysing the discourses involved as systems of signs, and looking for appropriate points of inter-relation between them. In this reconceptualisation of the ‘problem’ of transfer, the role of affective factors, previously under-examined in the literature, is highlighted. This revised version was published online in July 2006 with corrections to the Cover Date.     

Teachers' perceptions of students' excuses for academic difficulties

Ninety-seven teachers described situations in which their students experienced academic difficulties and gave reasons (excuses) to explain their difficulties. Teachers indicated whether or not they believed the reasons students gave, what they thought the “real” reasons for the students' difficulties were, and how they reacted and behaved toward the students. Analysis of teachers' reports indicated that students were most likely to attribute their academic difficulties to external, uncontrollable factors, whereas teachers tended to believe that the “real” reasons for students' difficulties were internal and controllable. Teachers reported that they would react in a positive manner toward the students whether or not they believed the reasons the students gave to explain their difficulties. Implications of these findings for student motivation are discussed.