Visual information for object identity in apparent movement

Apparent movement is used to examine the nature of the visual information which specifies object identity. Constructive feature-comparison theories rely on static formal information and predict that two phases of an apparent movement display must be featurally similar in order to appear as a single object in motion. An opposing Gibsonian model is based on abstract geometrical information and predicts that the two phases may differ radically in shape but must be ecologically transformable in order to be seen as a single object. The predictions are tested by presenting subjects with displays which are similar but not transformable, and transformable but dissimilar. Results show that the transformability of the display determines its perceived object identity, while featural similarity has no effect. An event theory of object identity is offered which claims that theaffordance structure of an event, determined by geometric invariants specifies object identity. ma-     

Bilateral apparent haptic movement

When Os are permitted to manipulate the interstimulus onset interval (ISOI) to obtain optimal apparent movement between two ipsilateral vibrotactile stimuli, a consistent quantitative relation between ISOI and stimulus duration appears. The present report describes conditions for movement between contralaterally-placed stimuli, and shows that whereas movement is qualitatively incomplete, the aforementioned relation is still evident. The results are discussed in the light of recent work in both visual apparent movement and complex patterns of stimulation on the skin.     

Temporal characteristics in apparent movement: Omega movement vs. PHI movement

A vertical line stimulus was presented alternately at two positions on an oscillo scope face, with no interstimulus interval. Observation of this stimulus produced haphazard alternation between a number of movement percepts, which were divided into four categories: phi, omega and partial movement, and no movement. Attention to one category did not increase the proportion of time movement in that category it was reported. Proportion of time reported for each category varied differentially as a function of alternation frequency. Upper and lower displacement amplitude limits were measured as a function of frequency for phi and omega movement. Both limits for omega movement differed from those for phi movement. The results imply that phi and omega movement involve separate processing stages in the visual system.     

Absence of masking in the path of apparent movement

Alternation of diagonal pairs of lights produced apparent movement which S could organize in either of two distinctly different ways, as instructed. The task was to detect movement of a weak probe light that either was or was not located in the path of the apparent movement, depending on the organization, stimulation being identical in the two cases. Results showed no evidence of path-specific masking.     

Kinetic occlusion by apparent movement

A small square and a large triangle below it were presented in the first frame. These were switched off and replaced by a triangle alone in the second frame, shifted horizontally and upwards. The triangle appeared to move obliquely, as expected, but most observers also saw the square moving horizontally and hiding behind the triangle, although there was no stimulus corresponding to it in the second frame. The visual system invokes the occlusion 'hypothesis' in order to explain the otherwise mysterious disappearance of the square. The experiment suggests that apparently intelligent solutions can be rapidly computed by the visual system.     

Directional information and apparent movement

The number of alternative directions that a point of light can take in the apparent movement produced by the successive exposure of two points of light may be considered its directional information. The present experiment is concerned with the relationship between such directional information and the threshold between apparent movement and apparent successiveness, the original hypothesis being that the greater the directional information, the higher the threshold of movement. In fact, contrary results were obtained. Thresholds were obtained under conditions where movement could occur in either eight directions or only in two directions, better and more persistent movement being found under the former conditions. But this result is obtained only when one measures thresholds by an ascending method: increasing the time separation between light points from optimal movement to successiveness. An hypothesis is proposed to explain the findings stated in terms of “attentional disarticulation”.     

Visual movement discrimination

Data are presented which support a mathematical model for visual movement perception. An observer’s ability to judge the relative position of two successively presented points of light in an otherwise dark room is shown to diminish as the inter-stimulus interval is increased. However, a measure of visual position memory appears to remain invariant a5 this interval is varied. Neither the degree of head stabilization nor whether viewing is monocular or binocular appreciably alters this measure.     

Position uncertainty and the perception of apparent movement

Two experiments compared the perception of apparent movement when the second of two successive stimuli always appeared in the same position and when it varied randomly between two spatial positions. The results of both experiments showed that foreknowledge of the position of the second stimulus does not facilitate the perception of apparent movement. Experiment 2 also clearly showed that the space-time relationships of Korte’s third law of apparent movement does not depend on foreknowledge of the position of the second stimulus. These findings imply that apparent movement in real time occurs after the second stimulus has been registered by the visual system. It suggests that apparent movement involves a delayed decision mechanism that stores the first stimulus, the interstimulus temporal interval, and the second stimulus, and then impletes a motion compatible with the stimulus information.     

Spatio-temporal probing of apparent rotational movement

A visual bar alternately presented in vertical and horizontal orientations appeared to rotate 90° through one of two pairs of opposite quadrants. Subjects judged whether a probe dot, interjected at some delay and angular deviation from the vertical bar, appeared before or after the bar “passed through” the corresponding angular orientation. When the motion was perceived in the probed quadrant, percent “before” responses dropped abruptly from near 100% to near 0% as delay increased, and the drop occurred at longer delays for probes at larger angular deviations. Under physically identical conditions, when the motion was perceived in an unprobed quadrant, percent “before” responses varied much less with delay and insignificantly with angular position. The accuracy of the judgments in the first case suggests the internal generation of an ordered sequence of intermediate representations during each apparent rotation.     

A pendulum phenomenon in the visual perception of apparent movement

In setting up an apparatus for studying the phenomenon of apparent movement it was noticed that, when a metronome was employed for making the electrical contacts in the light-circuits, the path of apparent movement between the two lights was curved instead of straight. This deviation could not be attributed to the presence of any distorting structure in the visual field, and an experimental investigation of the conditions of the phenomenon was begun. So far five different display conditions have each been observed by ten or eleven subjects individually. No subject saw more than one condition in the experimental series, and their reports indicate that the following factors, in order of importance, are effective in leading to the perception of curved apparent movement: (1) the shape of the light-stimuli, (2) the regularity of the rhythm of presentation, (3) the gradient of brightening and dimming of the lights and (4) the sound of the metronome in synchrony with the appearance of the lights.

The possible role of past experience in the perceptual process, and the relationship of this “pendular” phenomenon to Johansson's (1950) “wandering” phenomenon and to normal stroboscopic movement, are briefly discussed.     

Visual feedback,movement learning and the representation of movement

Two experiments on movement learning are reported where the orientation of a visual curve on a graphics terminal, defining a relatively complex arm movement, was either orthogonal to or compatible with the direction of the required movement. In addition, individual differences in spatial orientation and visualization abilities were correlated with motor performance. Results in both experiments showed that equivalent amounts of learning occurred in the two visual conditions. However, during transfer trials to the opposite condition, virtually no transfer occurred for the compatible group when they performed in the orthogonal condition whereas there was tranfer when the orthogonal group performed in the compatible condition. The results supported the idea that very early in learning the orthogonal orientation of visual curve promoted the development of an orientation processing stage which facilitated transrer performance of the orthogonal group. Integrating these results with the past literature on movement learning led to the notion that the orientation information processing stage can be considered a cognitive system that interacts with the image of the act. Finally, contrary to expectations, spatial orientation ability failed to account for any performance while spatial visualization ability moderately correlated with performance.