Postural requirements and progression velocity in young walkers

This article describes developmental changes in gait velocity and relates these changes to gait parameters that index postural stability (step width and lateral acceleration) and two components of velocity (cadence and step length). Five children were observed longitudinally over a 2-year period after onset of independent walking. Their range of speed increased threefold in the first 6 months of independent walking and then remained constant. In contrast, step width decreased approximately twofold. Whereas in adults, cadence and step length contribute approximately equally to speed, when infants first begin to walk independently, increase in velocity is due mostly to increased step length. After 5 months of independent walking, the pattern reverses, and increase in velocity is due primarily to increased cadence. The pattern remains constant over the next 18 months. From a developmental point of view, the data lead us to interpret early walking (the first 5 months) as a process of integration of postural constraints into the dynamic necessities of gait movement. A second phase, beginning after 4 to 5 months of independent walking, is considered to be a tuning phase characterized by a more precise adjustment of the gait parameters.     

Postural Requirements and Progression Velocity in Young Walkers

This article describes developmental changes in gait velocity and relates these changes to gait parameters that index postural stability (step width and lateral acceleration) and two components of velocity (cadence and step length).

Five children were observed longitudinally over a 2-year period after onset of independent walking. Their range of speed increased threefold in the first 6 months of independent walking and then remained constant. In contrast, step width decreased approximately twofold. Whereas in adults, cadence and step length contribute approximately equally to speed, when infants first begin to walk independently, increase in velocity is due mostly to increased step length. After 5 months of independent walking, the pattern reverses, and increase in velocity is due primarly to increased cadence. The pattern remains constant over the next 18 months. From a developmental point of view, the data lead us to interpret early walking (the first 5 months) as a process of integration of postural constraints into the dynamic necessities of gait movement. A second phase, beginning after 4 to 5 months of independent walking, is considered to be a tuning phase characterized by a more precise adjustment of the gait parameters.     

Who takes driving licence point recovery courses in France? Comparison between course-takers and ordinary drivers

A self-administered questionnaire was answered by 2014 drivers, 853 of whom were taking a course. The data were analyzed aiming to identify the factors that are linked to taking the course, i.e. to recurrent reoffending.The course-takers, of whom 89% were male, admitted committing more violations than the control group. They had more accidents. More male course-takers than controls reported not being happy, and they more frequently had high extroversion scores.The multivariate analysis showed that, among men, taking the course was associated with the mileage, the feeling of being almost certain to be charged for an offence and having a high risk of losing one’s licence, in addition to being young, having a large number of brothers and sisters, higher socio-occupational category and smoking. Among women, in spite of the small number of them on the course, the mileage, the feeling of having a high risk of losing one’s licence, driving alone, the mental representation of their own vehicle as an extension of their office, and defining themselves as liking to take risks during leisure activities were significantly linked to taking a points recovery course.Those taking the course were not therefore doing so by chance; they differed from the general population of drivers, which was also precisely described with regard to driving habits and representations.Recommendations are then made in order to redirect the content of courses more towards introspection than technical matters.     

Nesting of asymmetric functions in skilled bimanual action: dynamics of hammering behavior of bead craftsmen

In human manual activities, the two hands are often engaged in differentiated roles while cooperating with each other to produce an integrated outcome. Using recurrence methods, we studied the asymmetric bimanual action involved in stone bead production by craftsmen of different skill levels, and examined (a) how the control of unilateral movement is embedded in that of a bimanual system, and (b) how the behavior of a bimanual system is embedded in the context of the function performed in the world. Evidence was found that the movements of the two hands of experts were functionally linked, reflecting the roles assumed by each hand. We further found that only the dynamics of bimanual coordination of experts differentiated the functional requirements of different sub-goals. These results suggest that expertise in this skilled bimanual action lies in the nesting of functionally specific adjustments at different levels of a control hierarchy.     

Analysis of the transition from upright stance to steady state locomotion in children with under 200 days of autonomous walking

The aim of this paper was to study, from a developmental perspective, the transient phase of gait during the period between the standing posture and the achievement of steady state gait, using temporal and biochemical parameters. Eight children who had been walking autonomously for 90 to 200 days were observed. A total of 64 sequences of steps were analyzed. A sequence of steps began with the child standing still and was executed on a large force plate. From the determination of the instantaneous velocity of center of gravity results establish that, unlike adults, progression velocity in children end of the first step, but after two to four steps.The gait initiation process does not depend on the steady state velocity, but results from an initial fall. The duration of the movement up to the end of the first step is independent of the progression velocity but depends only upon the body mass and moment of inertia of the children.     

Tool use as a way to assess cognition: how do captive chimpanzees handle the weight of the hammer when cracking a nut?

Tool use in apes has been considered a landmark in cognition. However, while most studies concentrate on mental operations, there are very few studies of apes’ cognition as expressed in manual skills. This paper proposes theoretical and methodological considerations on movement analysis as a way of assessing primate cognition. We argue that a privileged way of appraising the characteristics of the cognitive abilities involved in tool use lies at the functional level. This implies that we focus on how the action proceeds, and more precisely, on how the functional characteristics of the task are generated. To support our view, we present the results of an experiment with five captive chimpanzees investigating the way how chimpanzees adapt to hammers of various weights while cracking nuts. The movement performed in the hammering task is analyzed in terms of energy production. Results show that chimpanzees mobilise passive as well as active forces to perform the compliant movement, that is, they modulate the dynamics of the arm/tool system. A comparison between chimpanzees suggests that experience contributes to this skill. The results suggest that in tool use, movements are not key per se, but only in as much as they express underlying cognitive processes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.