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.     

Age-Related Changes in Grip Force and Dynamics of Hand Movement

The authors investigated whether older adults (n = 16; mean age = 65 years) increased grip force to compensate for load force fluctuations during up and down movements more than young adults did (n = 16; mean age = 24 years) and whether older and young adults exhibited similar adaptation of grip force to alterations in friction associated with changes in object surface texture. As previously reported, older adults used a higher level of grip force than young adults during static holding. Increased grip force was observed in the older group during movement. The increase was appropriate to the lower coefficient of friction estimated for the older group. In both groups, grip force was greater with a smooth than with a rough surface (the latter having the higher coefficient of friction) during static holding and during movement. Moreover, grip force modulation was equally well synchronized with load force fluctuation during movement in the two groups. The authors concluded that changes in organization of grip force with age are well adapted to change in hand-object interface properties. Elevated grip force in older adults does not necessarily signify a fundamental change in synchronizing grip force modulation with load force fluctuation.     

Directional Variability of the Isometric Force Vector Produced by the Human Hand in Multijoint Planar Tasks

Numerous studies have examined control of force magnitude, but relatively little research has considered force direction control. The subjects applied isometric forces to a handle and the authors compared within-trial variability when force is produced in different directions. The standard deviation of the force parallel to the prescribed direction of force production increased linearly with the targeted force level, as did the standard deviation of the force perpendicular to the instructed direction. In contrast, the standard deviation of the angle of force production decreased with increased force level. In the 4 (of 8) instructed force directions where the endpoint force was generated due to a joint torque in only 1 joint (either the shoulder or elbow) the principal component axes in force space were well aligned with the prescribed direction of force production. In the other directions, the variance was approximately equal along the 2 force axes. The variance explained by the first principal component was significantly larger in torque space compared to the force space, and mostly corresponded to positive correlation between the joint torques. Such coordinated changes suggest that the torque variability was mainly due to the variability of the common drive to the muscles serving 2 joints, although this statement needs to be supported by direct studies of muscle activation in the future.     

The Micro-Structure of Tapping Movements in Children

In order to investigate the development of movement speed in relation to movement organization, children of 5, 6, 7, 8 and 9 years of age and adults carried out a reciprocal tapping task, in which time pressure and distance were manipulated. The duration, velocity, acceleration and accuracy of the movements were compared between age groups. Age differences appeared mainly in the homing time, not in the duration of the distance covering movement phase. Accuracy and velocity of the distance covering movement phase differed with age. Time pressure affected the homing time, but not the duration of the distance covering phase. Distance manipulation affected mainly the velocity and duration of the distance covering movement phase and the homing time. In the discussion it is contended that age differences in homing time may be related to both the accuracy of the distance covering movement phase and the rate of information processing of the subject.     

Bilateral Transfer as a Function of Mental Imagery

Three experiments are reported which investigate the role of mental imagery in the bilateral transfer from right to left hand of rotary pursuit skill. In Experiment 1 both mental imagery and physical rehearsal showed significant positive transfer relative to a control condition. However, work decrement may have accumulated and transferred in the physical rehearsal group thereby depressing this group’s left-hand performance. Experiment 2 was conducted under conditions designed to allow work decrement to dissipate prior to transfer to the contralateral limb. The data still showed no difference between physical re-hearsal and mental imagery. One interpretation of these data is that work decrement was present under both the physical rehearsal and mental imagery manipulations in Experiment 1. The data from Experiment 3 confirmed this interpretation as well as replicated the positive transfer effects found for mental imagery in Experiments 1 and 2. The data are discussed in terms of central versus peripheral explanatory mechanisms.     

Visual and Proprioceptive Adaptation of Arm Position in a Virtual Environment

The authors examined the resolution of a discrepancy between visual and proprioceptive estimates of arm position in 10 participants. The participants fixed their right shoulder at 0°, 30°, or 60° of transverse adduction while they viewed a video on a head-mounted display that showed their right arm extended in front of the trunk for 30 min. The perceived arm position more closely approached the seen arm position on the display as the difference between the actual and visually displayed arm positions increased. In the extreme case of a 90° discrepancy, the seen arm position on the display was very gradually perceived as approaching the actual arm position. The magnitude of changes in sensory estimates was larger for proprioception (20%) than for vision (< 10%).     

Charles Darwin,Paul MacLean,and the lost origins of “the moral sense”: Some implications for general evolution theory

This paper reports the discovery of a lost part of Charles Darwin's theory of the origins of “the moral sense,” its apparent corroboration by what are in effect lost findings by brain researcher Paul MacLean, and the implications of these findings for the advancement of General Evolution Theory and humanity.     

Quantification of dislocation structures at high resolution by atomic force microscopy of dislocation etch pits

Atomic force microscopy of dislocation etch pit structures is a convenient means of characterising the dislocation structure in etchable materials at high resolution for dislocation spacing extending down to 25 nm . This is demonstrated for single crystals of CaF₂. The local deformation zone generated around nanoindents at ambient temperature and the low-angle boundaries generated in the bulk during uniaxial compression at elevated temperatures are presented as examples.     

Validating Measures of Psychological Well-being by Contrasting Samples Employed in Hazardous and Less Hazardous Work

The study investigated whether differences between contrasting groups reflect significant differences in psychological well-being scores. Membership of hazardous vs. less hazardous occupations in the same profession served as proxy measures of well-being. Antonovsky's Sense of Coherence (SOC), Block & Kremen's Ego-resiliency, and Goldberg's Emotional Stability scales were validated. Study 1 compared mine rescue team members and ordinary miners (n = 34, 41) and Study 2 police special task force members and regular officers (n = 43, 41). In Study 1, SOC and job satisfaction predicted group membership. In Study 2, satisfaction with life and extraversion scales predicted group membership, as did SOC in a secondary analysis. The SOC scale could predict psychological well-being in hazardous work settings.     

The Design and Evaluation of a Hope Enhancement Programme for Adults

The study evaluated the effectiveness of a hope enhancement programme for a group of adults and its impact on general psychological well-being. The intervention programme focused on participants' abilities to set feasible goals, planning ways to reach those goals (pathways) and increase determination and motivation (agency) to reach these goals. The workshop-format programme, consisted of six two-hour sessions conducted over five days. A pre and post-test design included an experimental group (n = 8), control group (n = 8) and ‘chat group’ (n = 8). Findings indicated that the programme increased hope levels of the experimental group as indicated by the Hope Scale and the Hopefulness Subscale of the Hunter Opinions and Personal Expectations Scale. Well-being also improved as indicated by a significant increase in sense of coherence along with a positive change in satisfaction with life. Recommendations for future research were made.