Endre E. Kadar

A kinematic analysis of hand selection in a reaching task

A group of left- and right-handers was tested on a task requiring them to reach out and pick up an object with either the left or the right hand. We varied the eccentricity of the target object (a small glass) and the required accuracy level, by filling the glass with liquid. We recorded (a) frequency of left or right hand use, (b) hand preference using a handedness questionnaire, and (c) the trajectories of the reaches using a movement registration system. It was found that the stronger the hand preference, the further in contralateral space the shift occurred between left and right hand use. Not only did the transition point corresponding to the shift between the two hands correlate with the point where their deceleration times were equal, but these locations closely coincided. These findings suggest that people are highly skilled perceivers of their own action capabilities, and that they are able to select the action mode that is most suited to perform a given task. We argue that laterality should be understood in terms of asymmetries in action modes.

Toward an Ecological Field Theory of Perceptual Control of Locomotion

The field concept was introduced into physics in the 19th century. Soon afterward, some Gestaltists tried to use this approach to characterize the internal global brain process. Conversely, another Gestaltist, Lewin (1938), tried to develop a field description of the physical and social environment in which the brain field was immersed. Later, J. J. Gibson (Gibson & Crooks, 1938/1982) attempted to conceptualize the environment-organism interaction in field theoretic terms. First, he suggested that a dynamical field of safe travel may be used by drivers to control their automobiles in traffic while avoiding collisions. Later, Gibson and his colleagues (Gibson, 1950; Gibson, Olum, & Rosenblatt, 1955) showed, mathematically, how an optic flow field that actors may use in selecting approach paths for landing aircraft safely is available. Over the ensuing decades, the optic flow field description has provided a powerful and popular tool for addressing a number of diverse problems in visual perception as it pertains to the control of action. Although in a seminal article, Gibson (1958) outlined a general theory of visually controlled locomotion, a recently published special issue on this topic (in Ecological Psychology; W. H. Warren, 1998) revealed that in even simple tasks (e.g., steering), intentional and informational constraints are still not yet understood. This article critically reviews the history of field theoretical approaches to the problem of perceptual control of goal-directed behavior. In particular, our overview focuses on the historical sources and development of Gibsons field theoretic attempts to address the visual control of locomotion. Our overview also provides an evaluation of recent field theoretical efforts to describe animal-environment interactions. We conclude that the use of interaction fields seems to be the most promising current approach. Because these fields incorporate both perceptual and action variables, they provide a natural way to formulate the perceiving-acting cycle as the reciprocal interplay of information and control along a goal-directed path. Finally, field theory, we suggest, provides an important tool because its power can be readily extended to include other useful techniques as well (e.g., quantum mechanical path space formalisms).

Role of the Mirror-Neuron System in Cross-Education

The present review proposes the untested hypothesis that cross-education performed with a mirror increases the transfer of motor function to the resting limb compared with standard cross-education interventions without a mirror. The hypothesis is based on neuroanatomical evidence suggesting an overlap in activated brain areas when a unilateral motor task is performed with and without a mirror in the context of cross-education of the upper extremities. The review shows that the mirror-neuron system (MNS), connecting sensory neurons responding to visual properties of an observed action and motor neurons that discharge action potentials during the execution of a similar action, has the potential to enhance cross-education. After a literature search we narrowed the review to studies that examined healthy young adults who performed unilateral strength training and unilateral motor tasks with or without a mirror and assessed outcome measures in relation to the changes in brain activity, motor cortical excitability, and corticospinal excitability. We identified six chronic studies that examined the effects of unilateral strength training on neural adaptations and 15 cross-sectional studies that examined acute changes in brain activation, motor cortical and corticospinal excitability using imaging, electroencephalographic, magnetoencephalographic, and magnetic brain stimulation. There were two chronic and nine cross-sectional studies in which participants performed unilateral motor tasks while viewing the image of the active hand superimposed on the resting hand’s image. Collectively, the data suggest that the MNS is involved in cross-education and the hypothesis is tenable. However, future studies are needed to elucidate the precise mechanism of how the use of a mirror in a cross-education study augments transfer to the non-exercised limb. Recent studies show a strength-sparing effect in the immobilized arm after strength training of the free arm in healthy individuals, and improved bilateral function after unilateral exercise therapy in stroke patients. It is thus conceptually justified to conduct randomized clinical trials that supplement cross-education protocols with a mirror. Such a treatment could reduce muscle weakness caused by limb fractures, anterior-cruciate ligament reconstruction surgery, stroke, and other unilateral motor dysfunctions.

Odor-based navigational strategies for mobile agents

Although most species are sensitive to various chemicals, and olfactory skills such as search strategies for finding nutritious substance are seemingly simple, these basic skills are still not fully understood. Traditionally, chemotaxis has been considered as the fundamental chemosensory navigational mechanism for most species. Previous studies have demonstrated, however, that biased random walk is the more fundamental navigational strategy in various types of diffusion fields. Biased random walk is a robust and slow search process, but it has been shown that its efficiency can be enhanced if it is combined with chemotaxis. The present article summarizes previous findings of the authors in olfactory navigation and extends the work to searching in dynamic flow fields, including turbulence. In addition, a cooperative, multi-agent search method has been investigated and shown to be successful in enhancing search efficiency. The significance of these findings is discussed in the context of future plans to implement these strategies in experimental mobile robots.

From discrete actors to goal-directed actions: toward a process-based methodology for psychology

Studying social phenomena is often assumed to be inherently different from studying natural science phenomena. In psychology, this assumption has led to a division of the field into social and experimental domains. The same kind of division has carried over into ecological psychology, despite the fact that Gibson clearly intended his theory for both social and natural phenomena. In this paper, we argue that the social/natural science dichotomy can be derived from a distinction between hermeneutics and science that is deeply rooted in the atomistic, structuralist ontological tradition. We show that, from a process-based perspective, the central questions of hermeneutics (action of an individual within a context of possible actions), ecological psychology (behavior of an organism in an ecological niche) and physics (motion of a particle in a field) share a similar structure. Building on these ideas, we propose a common, process-based methodology for psychology that integrates field theory with insights from quantum mechanics to accommodate traditionally problematic concepts in natural science such as teleology and values. To demonstrate the feasibility of this approach, empirical findings on the paradigmatic problem of prospective control (such as gaze control in automobile driving in relation to perceptual tuning) are presented.

Co-Operative Smell-Based Navigation for Mobile Robots

This paper presents the latest developments from research carried out by the Portsmouth/Leeds group regarding odour source localisation using co-operating mobile robots. Previous studies have demonstrated the capability of individual mobile robots to find an odour source using the biologically inspired navigational strategies (chemotaxis and biased random walking (BRW)). A combined chemo- BRW strategy has also been presented and experimental studies have shown that a multi-robot approach can yield good results by improving the efficiency and robustness of the searches. New experimental results are presented in this paper which show that the use of co-operation offers good potential for improving the overall search performance in the odour source localisation problem.

Learning as progressive biasing of a random walk process: toward an ecological theory of exploratory learning

J. J. Gibson initially developed his theory of the perceptual control of action with an eye toward the perceptual control of locomotion. Subsequently, his theory has been generalized to many other tasks. Recent research has shown the importance of perceptual control skills in computer-based cognitive tasks. These results suggest that the problem of computer-interface design may be not only challenging in its own right but also theoretically promising as a way to investigate the exploratory learning of perceptual control skills. To test this premise, we used an existing instructional interface to capture the exploratory activities of novices as they learned to use a computer program. The aim of the research was to test a diffuse-control model of exploratory learning and a new evaluation methodology based on the model. Our results suggest that the model, which is based on ecological psychology principles, enhances our understanding of exploratory learning. Furthermore, the measures derived from the model provide a more detailed analysis of exploratory learning than current measures. Finally, the diffuse-control model and its derived measures proved to be an effective way to evaluate computer-interface design.

Drivers' Gaze Patterns in Braking From Three Different Approaches to a Crash Barrier

In our previous research, we found that drivers when engaged in straight-road driving, and also braking, tend to look in the direction of their intended movement regardless of speed or expertise (Rogers, Kadar, & Costall, this issue). Furthermore, gaze direction is highly constrained in braking, suggesting that speed control might be based on global optic flow. This study further investigates gaze when drivers are braking in front of a vertical barrier and either approaching the barrier orthogonally or from the right or the left. These three different directions of approach entail three different potential points of collision: the nose of the car, or the front right or left wheel. In all conditions, drivers directed their gaze in the direction of their movement. However, in the case of nonorthogonal approach, the drivers at the very end of their approach shifted their gaze away from their direction of travel and toward the potential collision point on the barrier. On the basis of these findings, we propose that drivers tend to rely on global optic flow to control their speed, but can also control speed by the local rate of optic expansion around the point of fixation (i.e., the point of potential collision).

Drifting towards a diffuse control model of exploratory motor learning: a comparison of global and within-trial performance measures

Abstract. Accurate measurement is crucial for understanding the processes that underlie exploratory patterns in motor learning. Accordingly, measures of learning should be sensitive to the changes that take place during skill acquisition. Most studies, however, use trial-based global measures that assess performance but do not actually measure gradual changes taking place within trials. The present study attempted to remedy this shortcoming by analysing a visual adaptation task, and comparing traditional global measures of learning with new, within-trial measures. Movement time was the only global measure sensitive to changes in the movement trajectory during learning. Three new measures were expected to reveal changes to the movement trajectory that are associated with learning: (i) the length of runs, (ii) change of trajectory angle in relation to the target, and (iii) drift (change in distance from the target). All three measures were sensitive to learning and indicated a gradual straightening of the movement trajectories over trials. Furthermore, three different methods to partition trajectories into segments were examined. The new within-trial measures, irrespective of partitioning method, prove promising for the development of a diffuse control model of exploratory learning.

Path space integrals for modeling experimental measurements of cerebellar functioning

A propagator for a path space integral can be used to represent the “tidal wave function” and provides a natural way to model a control signal that is temporally segmented by placement of pairs of stimulating and recording electrodes. Although care must be exercised in interpreting the resulting measurement, the technique should prove useful to experimenters who study cerebellar functioning.