Visually Controlled Locomotion: 40 years Later

Gibson's article, Visually Controlled Locomotion and Visual Orientation in Animals(1958/this issue), is the leading statement of a nonrepresentational, information-based approach to visual control. The core ideas he introduced 40 years ago resurface, explicitly or implicitly, in much contemporary work on perception and action in humans, insects, robots, and autonomous agents. The purpose of this special issue is to assess the continuing pertinence of these insights and illustrate current directions in research on visually controlled locomotion. In this article, I locate the 1958 article in the context of Gibson's emerging theory of perception, contrast information-based control with standard model-based and cybernetic control architectures, evaluate the current status of Gibson's visual control formulae, and situate visual control within an informational-dynamical approach to agent-environment systems. Locomotion is a biologically basic function, and if that can be accounted for then the problem of human space perception may appear in a new light. The question, then, is how an animal gets about by vision.     

Development of Visually Guided Locomotion

This article presents a developmental account of changes in the visual guidance of locomotion. In contrast to the impressive efficiency of adult locomotion, locomotor activity is not under prospective control at the onset of human mobility. Infants require extensive crawling and walking experience before responding adaptively to variations in the terrain. At the same time that they are learning to navigate in increasingly varied environments, their bodies and skills are rapidly changing. Learning generalizes from safe, flat ground to novel surfaces but it does not transfer to new methods of locomotion. We account for these patterns of generality and specificity of learning by focusing on the role of exploratory behavior in detecting threats to balance control.     

Visually Controlled Locomotion: Its Dependence on Optic Flow,Three-Dimensional Space Perception,and Cognition

Gibson (1958/this issue) and his followers have emphasized the role of optic flow in the control of locomotion. In recent years much research has been devoted to the visual control of aiming and braking, mainly in connection with terrestrial locomotion. The goal of this article is to broaden the topic empirically and theoretically. At the empirical level, we argue that there are a number of visually controlled maneuvers that need to be addressed for their own sake, for they involve more than can be learned from research on aiming and braking. At the theoretical level, we argue that optic flow needs to be supplemented by other explanatory primitives, including the actor's perception of three-dimensional spatial layout and the actor's cognitive representations of the spatial envelope and plant dynamics of his or her body or vehicle.     

Orientation Constancy in Neurons of Monkey Visual Cortex

We studied the effect of body tilt on the orientation selectivity of single neurons in the visual cortex of an alert monkey. The monkey performed a visual fixation task either in the upright position or with its whole body tilted about the naso-occipital (roll) axis by ±25° or ±30°. We determined the preferred stimulus orientation for 51 of 117 neurons in two or, if possible, three body positions (i.e. with the whole body upright, and tilted either left ear or right ear down). In striate cortex, most of the neurons were of a non-compensatory type, showing a change in the preferred orientation according to the body tilt and the estimated counterrolling of the eye. By contrast, about 40% of the neurons in prestriate cortex were of a compensatory type, preferring similar orientations in all body positions. This suggests that mechanisms which produce orientation constancy with respect to the direction of gravity are implemented at an early stage of cortical processing.     

方位维度视觉搜索的影响因素

Duncan等人认为,当目标和干扰子之间差异越大且干扰子彼此之间差异越小时,则目标搜索越快。他们的结论定性地描述了目标搜索斜率（反应时间对呈现项目数的函数）的决定因素。笔者从方位维度刺激关系方面进一步定量探究该问题,并提出决定因素为g(T, D, n)（目标方位和干扰子方位间的函数关系）。实验结果证实目标搜索斜率是由g(T,D,n)值决定,目标搜索斜率随g(T, D, n)值增大而减小,相同g(T, D, n)值条件的目标搜索斜率无显著差异     

Nature and Dynamics of Reference Frames in Visual Search for Orientation: Implications for Early Visual Processing

Visual detection of a line target differing in orientation from a background of lines is assumed to occur early in vision and to involve filter mechanisms acting in parallel over the visual field in retinotopic maps (Foster & Ward, 1991; Treisman, 1985; Wolfe, 1994). But retinotopicality does not imply that early vision takes place in a retinal reference frame. This article briefly reviews experiments on this issue and analyzes their implications regarding early visual processing. The review shows that the spatial frame of reference used in visual search for orientation is dynamically determined by various sensory cues to orientation (Marendaz, Stivalet, Barraclough, & Walkowiac, 1993; Stivalet, Marendaz, Barraclough, & Mourareau, 1995). These findings suggest that intersensory integration and perceptual organization are involved at a processing level preceding visual search. This functional viewpoint is discussed in relation to data from neuroscience and psychology (visual search, microgravity).     

Visual Evoked Potentials to Geometric Forms: Effects of Spatial Orientation

Five outlined geometric figures of equal contour length were presented monocularly below the fixation point (FP); an upright equilateral triangle (upright triangle), an inverted equilateral triangle (inverted triangle), an upright square (square), a 45°-tilted square (diamond) and a circle. The angular separation between FP and the top of the figures was held constant. Transient visual evoked potentials (VEPs) were recorded monopolarly from inion, 4, 7, 10 cm above it (l, l4, l7, l10) and Cz for ten subjects. The grand-averaged subtracted waves were obtained between the figure and blank (control) conditions. N1 (mean peak latency: 155 ms) and P2 (240 ms) waves were identified. ANOVAs were conducted for the latency and amplitude values. Main results were as follows: On the N1 amplitude at l4 and l, the upright triangle, inverted triangle and diamond figures evoked significantly larger responses than did the square and the circle. However, no significant difference was found among the former three figures. These findings on the N1 amplitude suggest that the effect of a triangle is orientation-free and that of a square is orientation-bound.     

Multifractality of Unperturbed and Asymmetric Locomotion

The purpose of this study was to explore the extent of multifractality in unperturbed and constrained locomotion, and to determine if multifractality predicted gait adaptability. Young, healthy participants (n?=?15) walked at preferred and slow speeds, as well as asymmetrically (one leg at half speed) on a split-belt treadmill. Stride time multifractality was assessed via local detrended fluctuation analysis, which evaluates the evolution of fluctuations both spatially and temporally. Unperturbed walking exhibited monofractal behavior. Asymmetric walking displayed greater multifractality in the faster moving limb, indicating more intermittent periods of extreme high or low variance. Multifractality was not associated with adaptation to asymmetric walking. These findings further suggest that unperturbed locomotion is monofractal and establish that perturbed walking yields multifractal behavior.     

Visually guided facial actions in rhesus monkeys

We trained 2 monkeys to display facial actions in response to corresponding arbitrary visual cues. Each monkey executed the task successfully, and each displayed two different facial actions corresponding to either hand-sign or color cues. More than 90% of the responses were correct for each monkey. These results provide evidence that monkeys can execute facial actions in response to conditioned visual cues in the absence of social context. These data suggest that facial actions of monkeys are flexible enough for use in further laboratory investigations—for example, in studies on the neural mechanisms underlying the execution of actions.     

Visually controlled space orientation in endogenous psychoses

The visual controlled behaviour in space is measured in 30 psychotic patients. In a room with a row of 8 equal chairs we measured the right-left-choice and the choice of distance. The neglect of the left chairs in patient with "distrust" and "delusion" let us suppose a right hemispherical dysfunction. There is no correlation between psychosis and choice of distance, but a good correlation between disturbed parental home and near distance.     

Visually guided collision avoidance and collision achievement

To survive on today's highways, a driver must have highly developed skills in visually guided collision avoidance. To play such games as cricket, tennis or baseball demands accurate, precise and reliable collision achievement. This review discusses evidence that some of these tasks are performed by predicting where an object will be at some sharply defined instant, several hundred milliseconds in the future, while other tasks are performed by utilizing the fact that some of our motor actions change what we see in ways that obey lawful relationships, and can therefore be learned. Several monocular and binocular visual correlates of the direction of an object's motion relative to the observer's head have been derived theoretically, along with visual correlates of the time to collision with an approaching object. Although laboratory psychophysics can identify putative neural mechanisms by showing which of the known correlates are processed by the human visual system independently of other visual information, it is only field research on, for example, driving, aviation and sport that can show which visual cues are actually used in these activities. This article reviews this research and describes a general psychophysically based rational approach to the design of such field studies.     

About Turn: The Visual Representation of Human Body Orientation Revealed by Adaptation

ABSTRACT— Body orientation provides an important cue to other individuals' focus of attention, particularly when one is viewing them at a distance. Single-cell recording in macaques has identified cells in the superior temporal sulcus that show a view-selective response to particular body orientations. Whether similar separable coding is found in humans is not known, and there is currently no functional account of the visual representation of seen body orientation. This study addressed this issue using visual adaptation. Experiment 1 demonstrated distinct channels that code left- and right-oriented bodies. Experiment 2 investigated whether the visual representation of body orientation is best accounted for by an opponent-coding system , which has been shown to account for the visual representation of facial identity, or by a multichannel system , which provides the optimal account of coding line orientation and direction of motion. Our results provide evidence for multichannel coding of seen body orientation, with separate channels (or neuronal populations) selectively tuned to different body directions.     

Metacognition in Humans and Animals

ABSTRACT— It has long been assumed that metacognition—thinking about one's own thoughts—is a uniquely human ability. Yet a decade of research suggests that, like humans, other animals can differentiate between what they know and what they do not know. They opt out of difficult trials; they avoid tests they are unlikely to answer correctly; and they make riskier "bets" when their memories are accurate than they do when their memories are inaccurate. These feats are simultaneously impressive and, by human standards, somewhat limited; new evidence suggests, however, that animals can generalize metacognitive judgments to new contexts and seek more information when they are unsure. Metacognition is intriguing, in part, because of parallels with self-reflection and conscious awareness. Consciousness appears to be consistent with, but not required by, the abilities animals have demonstrated thus far.     

Interaction Between Visually and Kinesthetically Triggered Voluntary Responses

A voluntary motor response that is prepared in advance of a stimulus may be triggered by any sensory input. This study investigated the combination of visual and kinesthetic inputs in triggering voluntary torque responses. When a visual stimulus was presented alone, subjects produced a fast and accurate increase in elbow flexion torque. When a kinesthetic stimulus was presented instead of the visual stimulus, subjects produced a similar response with a reduced response latency. When a visual stimulus was presented in combination with a kinesthetic stimulus, subjects initiated their responses after either a visual or a kinesthetic response latency, depending on the relative timing of the two stimuli. An analysis of response amplitude suggested that when visual and kinesthetic stimuli were combined, both stimuli triggered a response. The results are more consistent with a simple behavioral model of addition of visual and kinesthetic responses (which predicts that the response to combined stimuli should be the sum of individual responses) than with a model of exclusion of one response (which predicts that the response to combined stimuli should be identical to either the visual or the kinesthetic response). Because addition of visually and kinesthetically triggered responses produced a response with an erroneously large amplitude, it is suggested that visual and kinesthetic inputs are not always efficiently integrated.     

Asymmetries in the Regulation of Visually Guided Aiming

An experiment was conducted to examine the contribution of sensory information to asymmetries in manual aiming. Movements were performed in four vision conditions. In the full-vision condition (FV), subjects were afforded vision of both the hand and the target throughout the course of the movement. In the ambient-illumination-off condition (AO), the room lights were extinguished at movement initiation, preventing vision of the moving limb. In the target-off (TO) condition, the target was extinguished upon initiation of the movement. In a no-vision (NV) condition, ambient illumination was removed and the target was extinguished upon initiation of the response movement. Results indicated that accuracy was superior in the full-vision and target-off conditions and when movements were made by the right hand. Movements made by the right hand were also of shorter mean duration. The magnitudes of performance asymmetries were uninfluenced by vision condition. Analyses of movement kinematics revealed that movements made in conditions in which there was vision of the limb exhibited a greater number of discrete modifications of the movement trajectory. On an individual-trial basis, no relationship existed between accuracy and the occurrence of discrete modifications. These data suggest that although vision greatly enhances accuracy, discrete modifications subserved by vision reflect the imposition of nonfunctional zero-order control processes upon continuous higher-order control regimes.     

Locomotion, active choice, and spatial memory in children

In two studies, children between 4 and 6 years old were tested on a radial search task requiring nonredundant sampling of eight identically labeled positions in a room. In the training phase (5 days), children made free choices by walking between positions, were passively transported in a pushchair, actively directed their own route from a pushchair, or were led on foot to positions selected by the experimenter. When tested (whether walking or directing while seated in a pushchair), children who had either walked independently or directed the experimenter while being pushed performed competently; those led on foot without spatial choice performed almost as well. Only the children who had neither independent locomotor experience nor autonomous choice performed very poorly. The results are related to neurobiological models of spatial cognition and may have implications for the transportation of children with mobility problems.