The effect of sound on visual apparent movement

Twelve subjects found the longest possible interstimulus interval (ISI) at which they perceived continuous apparent motion of one light instead of partial motion or succession between two lights. In the visual condition, two lights only were presented. In the bimodal conditions, binaurally presented tones were presented synchronously with the lights, and the lights and tones were either spatially congruent (in phase) or incongruent (180 degrees out of phase). Bimodal presentations lowered the upper ISI threshold for the perception of visual apparent motion, and the reduction was greater when the tones and lights were spatially congruent. The threshold reduction may be caused by a perceptual inference about localization of the lights in space or by a change in visual persistence.     

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.     

Effects of living in the up-down inverted visual world on apparent movement

The purpose of this study was to examine whether a change of perceptual framework may affect the occurrence of apparent movement. Apparent movement was observed by one subject living over four days in the prismatically inverted visual world, because this situation was considered as the operation in which the subject was forced to change the perceptual framework to adapt himself to the novel environment. Apparent movement with two points was measured in vertical and horizontal configurations before wearing and after removing the prism as well as while wearing it. Analysis showed significant effects of prism-wearing on the occurrence of apparent movement in both vertical and horizontal configurations. Although further elaboration is required, an hypothesis was suggested from the viewpoint of the loss of visual position constancy.     

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.     

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”.     

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.     

Directional information and apparent movement—The apparent movement to apparent simultaneity threshold

This paper reports a study of changes in apparent movement to apparent simultaneity thresholds as a function of the directional information of the second point of light. An earlier paper (Jeeves and Bruner, 1956) reported changes in thresholds from apparent movement to apparent successiveness when the same experimental variable was manipulated. In interpreting the results the authors proposed an hypothesis in terms of “attentional disarticulation.” Brown (1956) commenting on this earlier paper put forward an alternative explanation of the results in conventional informational terms and he predicted the changes in the apparent movement to apparent simultaneity thresholds which should occur if studied under the same experimental conditions. He further showed that his predictions would differ from predictions made on the basis of our own explanation. The results of the experiment reported here uphold the predictions of our own earlier theory and fail to fit those made by Brown. However, in attempting to understand the results from the two experiments considered together, it is suggested that a factor must be included which was omitted from our own earlier explanation but emphasized by Brown. This factor as stated by Brown (1956) is “that the threshold for a discrimination tends to increase with the information content of any discrimination which has to be made concurrently.”     

Overshoot of curvature in visual apparent motion

If a curved line and a straight line are presented briefly, one above the other, in sequence to the eye, then, under appropriate conditions, visual apparent motion is obtained. Subjects report that the illusory figure moving and changing from the curved line to the straight line appears to overshoot the latter, gaining a small curvature in the opposite sense. Three experiments are described. In the first, the magnitude of this apparent curvature was quantified as a function of the delay between the onsets of the curved line and straight line (the stimulus onset asynchrony, SOA). It is shown that overshoot in curvature cannot be attributed to inappropriate patterns of eye fixations. In the second experiment, the stimulus configuration was modified to reveal the contribution to apparent curvature of classical curvature-contrast effects. Curvature overshoot due to apparent motion alone was thus estimated as a function of SOA. In the third experiment, an analogous position overshoot was measured for apparent motion elicited by two brief sequentially presented parallel line segments. It is argued that a combination of such position overshoots cannot explain curvature overshoot. Two schemes of a more general kind that might be used to interpret curvature overshoot are then outlined. One scheme is based on a neural-net model of apparent motion, and the other on a functional model of apparent motion that operates by laws analogous to those governing real physical motion.