Harmonic analysis of a complex motor behavior

This study deals with the learning of a complex motor task. The example used is rock climbing, where the subject's motricity is highly constrained by the natural environment. The working hypothesis is that the sensorimotor system searches for behavioral solutions characterized by minimal energy expenditure in the dissipation of forces. Harmonic systems — which satisfy this requirement — are used as models for testing the source signal defined by the acceleration curve at the learner's center of gravity. It is shown that only the dynamics of an expert's motor behavior are harmonic, while those of a beginner are stochastic (or chaotic). It is also shown that for experts, the process of adaptation to environmental constraints involves the relaxation of the dynamics and the ensuing emergence of a stable state which corresponds to a quasi-periodic attractor. A harmonic analysis is used to distinguish the environmental and intrinsic components of the behavioral dynamics, shown to result from the coupling of these two components via resonance.     

Agricultural research networks in sub-Saharan Africa: An analysis of the situation and its consequences

The purpose of this article is to compare the theory and reality of agricultural research networks in sub-Saharan Africa. Networking is a mode of organization that generally suits the new environmental conditions. The analysis of the agricultural research network environment in sub-Saharan Africa shows that when institutional networks started to proliferate, human and institutional conditions were not yet ripe. This explained some of the problems. Nowadays, conditions have improved. Despite all difficulties, networks have contributed to creating a scientific community, have participated in apportioning and even harmonizing research activities, and have made it possible to maintain research activities in countries going through a crisis. Marie de Lattre-Gasquet is a researcher from the Centre de coopération internationale en recherche agronomique pour le développement (CIRAD), in France. Within the external relations directorate of CIRAD, she has been responsible for the relationships between CIRAD and international organizations. She has also actively participated in the preparation of CIRAD’s long-term strategy. She worked for the International Service for National Agricultural Research (ISNAR) in The Netherlands from 1983 to 1985. She holds a Master in International Management (AGSIM, Thunderbird Campus) and a Doctorate in Economy (Université de Paris X). He is mostly working on the agricultural research networks in sub-Saharan Africa. He holds a diploma from the Institut National d’Agronomie—Paris Grignon.     

Neural correlates of partial transmission of sensorimotor information in the cerebral cortex

Using single neuron recordings in monkey primary motor (MI) cortex, two series of experiments were conducted in order to know whether response preparation can begin before perceptual processing finishes, thus providing evidence for a temporal overlap of perceptual and motor processes.

In Experiment 1, a “left/right, Go/No-Go” reaction time (RT) task was used. One monkey was trained to perform wrist flexion/extension movements to align a pointer with visual targets. The visual display was organized to provide a two-dimensional stimulus: side (an easy discrimination between left and right targets) which determined movement direction, and distance (a difficult discrimination between distal and proximal targets) which determined whether or not the movement was to be made. Changes in neuronal activity, when they were time-locked to the stimulus, were almost similar in the Go and No-Go trials, and when they were time-locked to movement onset, were markedly reduced in No-Go as compared to Go trials.

In Experiment 2, a stimulus-response compatibility (SRC) task was used. Two monkeys were trained to align a pointer with visual targets, on either left or right. In the spatially “compatible” trials, they had to point at the stimulus position, whereas in the “incompatible” trials, they had to point at the target located in the opposite side. For 12.5% of neurons, changes in activity associated with incompatible trials looked like changes in activity associated with movements performed in the opposite direction during compatible trials, thus suggesting the hypothesis of an automatic activation of the congruent, but incorrect response.

Results of both experiments provide evidence for a partial transmission of information from visual to motor cortical areas: that is, in the No-Go trials of the first task, information about movement direction, before the decision to perform or not this movement was made, and, in the incompatible trials of the SRC task, information about the congruent, but incorrect response, before the incongruent, but correct response was programmed.     

Visual stability with goal-directed eye and arm movements toward a target displaced during saccadic suppression

This experiment tested whether the perceived stability of the environment is altered when there is a combination of eye and visually open-loop hand movements toward a target displaced during the eye movements, i.e., during saccadic suppression. Visual-target eccentricity randomly decreased or increased during eye movements and subjects reported whether they perceived a target displacement or not, and if so, the direction of the displacement. Three experimental conditions, involving different combinations of eye and arm movements, were tested: (a) eye movements only; (b) simultaneous eye and rapid arm movements toward the target; and (c) simultaneous eye and arm movements with a restraint blocking the arm as soon as the hand left the starting position. The perceptual threshold of target displacements resulting in an increased target eccentricity was greater when subjects combined eye and arm movements toward the target object, specially for the no-restraint condition. Subjects corrected most of their arm trajectory toward the displaced target despite the short movement times (average MT = 189 ms). After the movements, the null error feedback of the hand's final position presumably overlapped the retino-oculomotor signal error and could be responsible for the deficient perception of target displacements. Thus, subjects interpreted the terminal hand positions as being within the range of the endpoint variability associated with the production of rapid arm movements rather than as a change of the environment. These results suggest that a natural strategy adopted for processing spatial information, especially in a competing situation, could favour a constancy tendency, avoiding systematic perception of a change of environment for any noise or variability at the central or peripheral levels.     

Generating multiple samples of multivariate data with arbitrary population parameters

A method of generating any number of score and correlation matrices with arbitrary population parameters is described. EitherZ scores or stanines are sampled from a normal population to represent factor scores by an IBM 1620 program. These are converted to variates from a population with an a priori factor structure. The effectiveness of the method is illustrated from research data. Some further modifications and uses of the method are discussed.     

Neuropsychological profile of adult dyslexics

One hundred and fifteen adults with well-documented childhood reading status underwent a series of neuropsychological tests including tests of memory, attention, phonological processing, and visual perceptual skills in an attempt to define the neuropsychological profile of dyslexia in adulthood. Compared to a normal nonreading disabled sample, subjects with a history of reading disability performed consistently poorer on most neuropsychological tests. However, after covarying for intelligence and socioeconomic status, only tests of rapid naming, phonological awareness, and nonword reading were significant discriminating measures. The hypothesis that deficits in phonological processing comprise the core cognitive deficits in adults with a history of reading disability was supported. Independent of current adult reading ability, measures of nonword reading, phonological awareness, and rapid naming serve as indicators of a childhood history of reading disability.     

Community psychology into the 1990s: Capitalizing opportunity and promoting innovation

Political and social changes during the last decade and their implications for community psychology research and practice are discussed. Shifting responsibility for social problems, economic considerations, and levels of citizen concern and involvement in community problem solution are considered stimuli for new opportunities for innovation and change. The discipline is challenged to renew efforts in the promotion of innovation and to develop and disseminate interventions that result in modification in the role relationships characterizing the ecology of social problems.     

Sex and attitude distortion: Ability of females and males to fake liberal and conservative positions regarding changing sex roles

Scales designed to measure attitudes toward changing sex roles are vulnerable to the effects of social desirability. The purpose of this study was to assess the differences in this vulnerability or fakeability between an older scale, the Attitudes Toward Women Scale (AWS) and a more current scale, the Bias in Attitudes Survey (BIAS). Results suggest that, when asked to do so, females are able to present themselves as liberal or conservative on either scale. Males can manipulate the concepts of the AWS as directed, but are less able to do so with the concepts on the BIAS. Implications for the measurement of sex-role attitudes are discussed.     

Relations between visceral and behavioral function in men at bedrest

Multiple physiological measurements as well as a self-assessment of arousal was made in eight men on the first, third, and fifth days of bedrest. On the third day, additional measurements of performance on memory and dexterity tasks were made. Univariate analysis did not reveal any physiological variable to either predict subsequent performance well or to co-vary acutely with it; however, self-rating scores did prove to be useful predictors of subsequent performance. Principal components analysis suggested an“alertness” factor comprised of physiological measures as well as selfratings which helped in predicting better performance. Although the individual patterns of correlations between variables on each of the three test days was variable, even more variability between subjects was found on the performance testing day. We believe this effect of behavioral activation may be due to the injection of common, slow temporal trends into many of the different data sets.