Validation of a full body 3-D dynamic linked segment model

In studies related to human movement, linked segment models (LSM's) are often used to quantify forces and torques, generated in body joints. Some LSM's represent only a few body segments. Others, for instance used in studies on the control of whole body movements, include all body segments. As a consequence of the complexity of 3-dimensional (3-D) analyses, most LSM's are restricted to one plane of motion. However, in asymmetric movements this may result in a loss of relevant information. The aim of the current study was to develop and validate a 3-D LSM including all body segments. Braces with markers, attached to all body segments, were used to record the body movements. The validation of the model was accomplished by comparing the measured with the estimated ground reaction force and by comparing the torques at the lumbo-sacral joint that resulted from a bottom-up and a top-down mechanical analysis. For both comparisons, reasonable to good agreement was found. Sources of error that could not be analysed this way, were subjected to an additional sensitivity analysis. It was concluded that the internal validity of the current model is quite satisfactory.     

A transactional analysis of biobehavioral systems

The system of behavior [B] consists of those transactional interrelationships between organism [O] and environment [E] that govern their commerce. The biological significance of such [O]-[E] interrelationships, their truing through learning, as well as those systems involved in the subordinate and superordinate regulation of behavior, are clear when life, itself, is seen as an emergent property of the [O]-[E] complex. In addition, a systems view of these hierarchically organized complexities suggests that they adaptively self-stabilize and self-organize, over time, as they participate in [L], the organism-environment complex. Such a transactional analysis of biobehavioral systems resonates well with the most basic axioms of Pavlov’s paradigm.     

Fourier analysis of movement patterns in pigeons

Fourier analysis describes the amount of variation in a time series by partitioning it into sinusoids of different amplitudes and wavelengths and quantifying the extent to which these waves are synchronized. The importance of a given wave is represented by its contribution to the explained variance of the time series. To illustrate its potential application to the study of movement, Fourier analysis was used to quantify the movement patterns of 2 pigeons on a variable-interval (VI) and a variable-time (VT) schedule of reinforcement. For comparison, the movements of 2 pigeons that did not receive reinforcement were similarly analyzed. Characteristic frequencies were higher during VI than during VT, and relatively low during nonreinforcement. We concluded that Fourier analysis can be used to represent movement patterns compactly, study their periodicity, stereotypy, and resonance, and assist in computer simulations and models of movement.     

Meaning,amount of processing,and memory for words

Two experiments were carried out in order to try to resolve the controversy about whether the semantic processing of a word necessarily involves all the elements of its meaning. In the first experiment, subjects categorized a list of auditorially presented words according to whether or not they were natural consumable solids (e.g., “apple“). They were then given an unexpected test of their ability to recall the whole list, which contained equal numbers of words with none, one, two, or all three of the target components. The results confirmed the prediction that the greater the number of components a word has in common with a target category, the better it will be recalled. The second experiment used a visual presentation of a list of words, which subjects scanned for members of a particular target category. There were four different target categories assigned to independent groups of subjects. The results again confirmed the prediction. On the assumption that memorability in such tasks is determined by amount of processing, we conclude that some elements of the meaning of a word can be processed without having to process all of them.     

The children of Mexican-American migrant workers: A population at risk?

The present study assessed intellectual, academic, and emotional strengths and weaknesses for a group of Mexican-American children of migrant farm workers. In order to test the vulnerability hypothesis, the test profiles of these children were contrasted with those of two groups of black children with similar demographic makeup. The children of one group (Clinical Black) had been referred previously for a psychological consultation while the children of the other (Nonreferred Black) had not. Across dependent measures, between-groups contrasts tended to describe the scores of the Migrant children as similar to those of the Clinical Black children and significantly below those of the Nonreferred Black children. The findings suggested specific intellectual, academic, and emotional vulnerabilities of the Migrant children and demonstrated the need to develop ameliorative programs for these children.The authors wish to thank the staff of C & Y, University of Virginia Hospital, especially Ms. Deborah Johnson and Ms. Suzanne Canale, whose cooperation and assistance made this project possible.