Active gaze, visual look-ahead, and locomotor control

The authors examined observers steering through a series of obstacles to determine the role of active gaze in shaping locomotor trajectories. Participants sat on a bicycle trainer integrated with a large field-of-view simulator and steered through a series of slalom gates. Steering behavior was determined by examining the passing distance through gates and the smoothness of trajectory. Gaze monitoring revealed which slalom targets were fixated and for how long. Participants tended to track the most immediate gate until it was about 1.5 s away, at which point gaze switched to the next slalom gate. To probe this gaze pattern, the authors then introduced a number of experimental conditions that placed spatial or temporal constraints on where participants could look and when. These manipulations resulted in systematic steering errors when observers were forced to use unnatural looking patterns, but errors were reduced when peripheral monitoring of obstacles was allowed. A steering model based on active gaze sampling is proposed, informed by the experimental conditions and consistent with observations in free-gaze experiments and with recommendations from real-world high-speed steering.     

Discrete visual samples may control locomotor equilibrium and foot positioning in man

The static or dynamic visual cues required for equilibrium as well as for foot guidance in visually guided locomotion in man were studied using a variety of locomotion supports and illumination and visual conditions. Stroboscopic illumination (brief flashes) and intermittent lighting (longer flashes) were used to control and to vary the visual sampling frequency of static (positional/orientational) visual cues. There were three main findings: First, visual control of foot positioning during locomotion over a narrow support depends mainly upon the availability of high frequency static visual cues (up to about 12 Hz); and third, static visual cues required for equilibrium control are extracted from both the peripheral and the central visual field. Assuming that discrete demands for feedback occur, a simple probabilistic model was proposed, according to which the mean time that elapses following presentation of static visual cues about positions or changes of position accounts for the differences in the difficulty of the various illumination conditions.     

The role of visual information in control of a constrained locomotor task

The nature of visually guided locomotion was examined in an experiment where subjects had to walk to targets under various conditions. Target distance was manipulated so that subjects had to (a) lengthen their paces in order to hit the target; (b) shorten their paces; (c) make no adjustments to their standard pace length at all. They did this under four visual conditions: (a) normal vision; (b) with vision restricted to a "snapshot" each time the foot that was to be placed on the target was on the ground; (c) with a snapshot each time the foot to be placed was in the swing phase; and (d) no vision after departure fro the target. The results show that the subjects succeed in reaching the target in most cases. However, the smoothness and fluidity of their movements vary significantly between conditions. Under normal vision or where visual snapshots are delivered when the pointing foot is on the ground, locomotion is smoothly regulated as the subjects approach the target. where snapshots are delivered when the pointing foot is in the swing phase, regulation becomes clumsy and ill coordinated. Where no vision is available at all during the approach, adjustments are made, but these are least coordinated of all. The results show that well-coordinated visual regulation does not require continuous visual guidance but depends on intermittent information being available at the appropriate times in the action sequence. Such timing is often more important than the total amount of information that is available for guidance.     

A procedure for studying strategy development in humans

An early version of the computer gameStar Trek was modified to conduct behavioral research. By appropriate use of the starship’s weapon and defense systems, the player can kill enemy ships and avoid destruction. The player’s moves, as well as the time and state of the game environment when each move occurs, are recorded. The procedure tracks performance changes over time very well, and allows the dissection of performance into sequences of commands that reflect the subject’s play strategy. Computer games such asStar Trek could be the basis for experiments that bridge the gap between operant and cognitive research.     

Blocking and pseudoblocking: New control experiments with honeybees

Prompted by doubts about the adequacy of the various control procedures long used in research on blocking, we repeated some earlier experiments with honeybees that had given the appearance of forward, concurrent, and backward blocking. The new experiments differed from the earlier experiments only in that the target stimulus was omitted during the training and was encountered for the first time in the test. In the new experiments, just as in the earlier experiments, the blocking groups responded less to the target stimulus than did the control groups. The results show that the effects of the different treatments of nontarget stimuli commonly compared in blocking experiments may generalize to the target stimulus and thus affect responding to that stimulus independently of experience with it. Implications for research on blocking in honeybees and other animals are considered.     

Blocking and pseudoblocking: new control experiments with honeybees

Prompted by doubts about the adequacy of the various control procedures long used in research on blocking, we repeated some earlier experiments with honeybees that had given the appearance of forward, concurrent, and backward blocking. The new experiments differed from the earlier experiments only in that the target stimulus was omitted during the training and was encountered for the first time in the test. In the new experiments, just as in the earlier experiments, the blocking groups responded less to the target stimulus than did the control groups. The results show that the effects of the different treatments of nontarget stimuli commonly compared in blocking experiments may generalize to the target stimulus and thus affect responding to that stimulus independently of experience with it. Implications for research on blocking in honeybees and other animals are considered.     

Perceptual scale expansion: an efficient angular coding strategy for locomotor space

Whereas most sensory information is coded on a logarithmic scale, linear expansion of a limited range may provide a more efficient coding for the angular variables important to precise motor control. In four experiments, we show that the perceived declination of gaze, like the perceived orientation of surfaces, is coded on a distorted scale. The distortion seems to arise from a nearly linear expansion of the angular range close to horizontal/straight ahead and is evident in explicit verbal and nonverbal measures (Experiments 1 and 2), as well as in implicit measures of perceived gaze direction (Experiment 4). The theory is advanced that this scale expansion (by a factor of about 1.5) may serve a functional goal of coding efficiency for angular perceptual variables. The scale expansion of perceived gaze declination is accompanied by a corresponding expansion of perceived optical slants in the same range (Experiments 3 and 4). These dual distortions can account for the explicit misperception of distance typically obtained by direct report and exocentric matching, while allowing for accurate spatial action to be understood as the result of calibration.     

Biomechanics of normal and pathological gait: implications for understanding human locomotor control

The biomechanical (kinetic) analysis of human gait reveals the integrated and detailed motor patterns that are essential in pinpointing the abnormal patterns in pathological gait. In a similar manner, these motor patterns (moments, powers, and EMGs) can be used to identify synergies and to validate theories of CNS control. Based on kinetic and EMG patterns for a wide range of normal subjects and cadences, evidence is presented that both supports and negates the central pattern generator theory of locomotion. Adaptive motor patterns that are evident in peripheral gait pathologies reinforce a strong peripheral rather than a central control. Finally, a three-component subtask theory of human gait is presented and is supported by reference to the motor patterns seen in a normal gait. The identified subtasks are (a) support (against collapse during stance); (b) dynamic balance of the upper body, also during stance; and (c) feedforward control of the foot trajectory to achieve safe ground clearance and a gentle heel contact.     

Remote control and children's understanding of robots

Children use goal-directed motion to classify agents as living things from early in infancy. In the current study, we asked whether preschoolers are flexible in their application of this criterion by introducing them to robots that engaged in goal-directed motion. In one case the robot appeared to move fully autonomously, and in the other case it was controlled by a remote. We found that 4- and 5-year-olds attributed fewer living thing properties to the robot after seeing it controlled by a remote, suggesting that they are flexible in their application of the goal-directed motion criterion in the face of conflicting evidence of living thing status. Children can flexibly incorporate internal causes for an agent’s behavior to enrich their understanding of novel agents.     

Response frequency equalization: A bias model for psychophysics

A model for response bias in psychophysics is derived. Of the model’s two aspects, one is concerned with the generation of sensory states and the other with rules for transforming sensory states into responses. The model incorporates the bias rule that Ss tend to use available responses with equal frequency. Applications to experiments which use the method of constant stimuli are discussed. Despite the contrary claims of Restle and Levison (1971), the model not only predicts their data quite well but also, under certain conditions, does so better than the theory of adaptation level used by Restle and Levison themselves.     

A working memory model improves cognitive control in agents and robots

Cognition entails those mental processes enabling understanding the current situation through senses, experience, and thought, and supporting the acquisition of new knowledge. A fundamental contribution in cognition is offered by the working memory, that is a small, short-term memory containing and protecting from interference goal-relevant pieces of information. Grounding our work on biological and neuroscientific studies, we modeled and implemented working memory processes in a software model, IDRA-WM, that can simultaneously act as short-term memory and actions generator, thanks to the use of a reinforcement-driven mechanism for chunk selection. Moreover our system integrates the functions of the working memory with a basic action planner. We tested the model with robot relevant tasks to assess whether the proposed solution can learn to solve a problem on the basis of a delayed reward. The experimental results indicate that IDRA-WM is able to solve even those tasks that do not provide immediate reward after an action.     

A two-point visual control model of steering

When steering down a winding road, drivers have been shown to use both near and far regions of the road for guidance during steering. We propose a model of steering that explicitly embodies this idea, using both a 'near point' to maintain a central lane position and a 'far point' to account for the upcoming roadway. Unlike control models that integrate near and far information to compute curvature or more complex features, our model relies solely on one perceptually plausible feature of the near and far points, namely the visual direction to each point. The resulting parsimonious model can be run in simulation within a realistic highway environment to facilitate direct comparison between model and human behavior. Using such simulations, we demonstrate that the proposed two-point model is able to account for four interesting aspects of steering behavior: curve negotiation with occluded visual regions, corrective steering after a lateral drift, lane changing, and individual differences.     

Intuitive control of mobile robots: an architecture for autonomous adaptive dynamic behaviour integration

In this paper, we present a novel approach to human–robot control. Taking inspiration from behaviour-based robotics and self-organisation principles, we present an interfacing mechanism, with the ability to adapt both towards the user and the robotic morphology. The aim is for a transparent mechanism connecting user and robot, allowing for a seamless integration of control signals and robot behaviours. Instead of the user adapting to the interface and control paradigm, the proposed architecture allows the user to shape the control motifs in their way of preference, moving away from the case where the user has to read and understand an operation manual, or it has to learn to operate a specific device. Starting from a tabula rasa basis, the architecture is able to identify control patterns (behaviours) for the given robotic morphology and successfully merge them with control signals from the user, regardless of the input device used. The structural components of the interface are presented and assessed both individually and as a whole. Inherent properties of the architecture are presented and explained. At the same time, emergent properties are presented and investigated. As a whole, this paradigm of control is found to highlight the potential for a change in the paradigm of robotic control, and a new level in the taxonomy of human in the loop systems.     

Organization in visual episodic memory: relationships between verbalized knowledge, strategy use, and performance

Relationships between verbalized knowledge (metamemory), strategy use, and performance were examined in a memory task for visually presented episodes. Kindergarten, second-grade, and fifth-grade students were asked to reconstruct a sequence of pictures forming an episode from an array of original pictures and foils. The episodes varied on two dimensions; materials type and the logic of the sequence. Materials were either typical (familiar animal characters and scenes) or atypical (geometric figures) story materials. Sequences either readily conveyed a story (logical) or were rearranged to present a random ordering of pictures (illogical). Children were questioned about their use of a story line to help remember the picture sequences (general questioning) and were asked more specific questions concerning the reasons for their picture selection during the task (specific questioning). Children at all ages recalled logical sequences better than illogical ones. Second- and fifth-grade children recalled animal episodes better than geometric form episodes. Children at all ages showed a correspondence between strategy use and metamemory as assessed by verbalization of relationships among pictures during the specific questioning. However, when the more typical general question format was used to assess metamemory, strategy use preceded verbalized knowledge of strategy use.     

Some characteristics of EMG patterns during locomotion: implications for the locomotor control process

Myoelectric signals from several muscles of the lower limb were studied under various speed and stride length conditions. The main purpose was to determine invariant and variant features among these myoelectric patterns. A pattern recognition algorithm was used to analyze these activity patterns. Within-condition analysis revealed some common features among the EMG patterns. This suggests that the nervous system does not have to generate all the muscle activity patterns, only the common features that can, in appropriate combination, produce the necessary activity patterns. From the across condition analysis, the following rules emerged. First, both phasic component and magnitude (d.c. level) of the muscle activity patterns have to be modulated to meet the demands imposed by the various conditions. Second, the variability in the proximal muscle activity patterns across conditions are higher than the distal muscle activity patterns. Within each group, the extensor muscles and double-jointed muscles show greater variability than the flexor muscles and single-jointed muscles. And finally, the changes in the average value (d.c. level) of the muscle activity patterns across conditions are not uniform but show muscle and task specificity. For example, within the speed condition, the increase in d.c. level of the extensors with speed of locomotion show a proximal to distal trend. Based on these results, a conceptual model for the human locomotor control process is proposed.     

Familiarity, redundancy, and the spatial control of visual attention

Highly familiar letter sequences (English words) in noncued portions of a tachistoscopic display were shown to substantially reduce accuracy of partial report. These findings suggest that in addition to facilitating character scanning, familiarity may operate in automatically directing attentional resources to a particular spatial region of a display. Such attentional capture may be disruptive if the material to be reported is presented at another location.