Pulfrich Effect and the Filling in of Apparent Motion

Perception ◽  
1976 ◽  
Vol 5 (2) ◽  
pp. 187-195 ◽  
Author(s):  
Michael J Morgan
Keyword(s):  
Eye Movements ◽  
Apparent Motion ◽  
Visual Direction ◽  
Moving Target ◽  
Alignment Technique ◽  
Pulfrich Effect ◽  
Series Of Experiments ◽  
Tracking Eye Movements ◽  
As If

In the stroboscopic version of the Pulfrich effect a filter is able to induce depth shifts in a target as if the latter were moving continuously, rather than merely occupying a series of discrete positions. This was examined in a further series of experiments, in which a visual alignment technique was used to measure the perceived visual direction of an apparently moving target in intervals between its presentations. Results showed that the target has approximately the visual direction that it would have if it were moving continuously. This ‘filling in’ of apparent motion was shown to occur before the level of stereopsis. The possible influence of tracking eye movements is discussed.

Spatiotemporal Filtering and the Interpolation Effect in Apparent Motion

Perception ◽  
1980 ◽  
Vol 9 (2) ◽  
pp. 161-174 ◽  
Author(s):  
Michael J Morgan
Keyword(s):  
Apparent Motion ◽  
Spatial Position ◽  
Moving Target ◽  
Periodic Modulation ◽  
Continuous Motion ◽  
Spatiotemporal Filtering ◽  
Alignment Technique ◽  
As If

A target moving in discrete spatial steps with an appropriate interstep interval (ISI) can appear visually as if it is in continuous motion. The momentary spatial position of such a target is interpolated by the observer between its real physical positions. The extent of this interpolation was measured by a vernier alignment technique, and was found to decrease as the ISI was lengthened. A discretely moving target may be described as a continuously moving target on which is superimposed a periodic modulation of spatial position. It is shown that the traditional ‘staircase’ stimulus for apparent motion can be generalized to include other kinds of periodic modulation. With the use of various analog-filtered and digitally filtered versions of staircase stimuli with different ISIs, it was shown that the phenomenal interpolation of a periodically modulated moving target was affected only when the frequencies of modulation were less than about 25 Hz. The spatial amplitude of the modulation also has some effect.

Interocular Delay Produces Depth in Subjectively Moving Noise Patterns

1980 ◽  
Vol 32 (3) ◽  
pp. 387-395 ◽  
Author(s):  
M. J. Morgan ◽  
Roger Ward
Keyword(s):  
Apparent Motion ◽  
Visual Noise ◽  
Moving Target ◽  
Dynamic Visual Noise ◽  
Spatial Disparity ◽  
Depth Effect ◽  
Retinal Disparity ◽  
As If

Brief apparent motion sequences were introduced into a dynamic visual dot display by spatially shifting selected dots between successive frames. This causes the display to look as if it is drifting continuously in one direction. When such a display is observed with an interocular delay the drifting dots appear to be displaced in depth, even though there is no conventional retinal disparity in the display. We found that the magnitude of this depth shift increased with the duration of the apparent motion sequences. With sequences of five or more frames duration the depth effect was very similar to that which would have been predicted with a continuously moving target. With briefer sequences the size of the depth effect decreased rapidly. We suggest that apparent motion cascades form the basis of Tyler's dynamic visual noise stereophenomenon, and we question his “random spatial disparity” hypothesis.

A Delayed Induced-Motion Illusion

Perception ◽  
1978 ◽  
Vol 7 (1) ◽  
pp. 85-89 ◽  
Author(s):  
George M Robinson ◽  
Janice Moulton
Keyword(s):  
Eye Movements ◽  
Visual Illusion ◽  
Perceptual Processing ◽  
Moving Target ◽  
Fixed Target ◽  
Aircraft Accidents ◽  
Motion Cues ◽  
Wide Range ◽  
Induced Motion ◽  
Series Of Experiments

We report a striking visual illusion which involves an induced motion that is delayed in time. An observer visually tracks a moving target in the neighborhood of a fixed target. The fixed target appears to be entrained by the moving target and appears to follow its movements after a lag of 0.33 second. A series of experiments showed that while the illusion depends on low background salience it obtains with both smooth and oscillatory motion in all directions including depth, under monocular and binocular viewing, in the absence of vestibular and kinesthetic motion cues or eye movements, and under a wide range of relative and absolute target luminance and position. The strength of the illusion and the magnitude of the induced movement's delay seem not to depend on any of the above factors. The illusion, by resisting a peripheral explanation, may provide some clues to central perceptual processing. In addition, we suggest the possibility that errors of judgment based on the nonveridical perception of motion displaced in time may play a role in nighttime automobile and aircraft accidents.

The Aftereffect of Tracking Eye Movements

Perception ◽  
1976 ◽  
Vol 5 (3) ◽  
pp. 309-317 ◽  
Author(s):  
Michael J Morgan ◽  
Roger M Ward ◽  
Edward M Brussell
Keyword(s):  
Eye Movements ◽  
Opposite Direction ◽  
Optokinetic Nystagmus ◽  
Motion Aftereffect ◽  
Moving Target ◽  
Background Stimulation ◽  
Tracking Eye Movements ◽  
Stimulation Of

When observers tracked moving stripes across a background either of stationary stripes, or of stripes moving in the opposite direction, they saw a clear motion aftereffect when the stripes stopped moving. The direction of this aftereffect was opposite to that of the previously tracked stripes, and was thus the same as the direction of the retinal movement of the non-tracked stripes. This aftereffect of tracking was shown not to depend upon slippage of the tracked contours on the retina during tracking, or upon the saccadic phase of optokinetic nystagmus. The effect showed storage over a period of time with the eyes shut. It appears that the effect is due to induced movement, and arises originally from stimulation of the retina by background contours in the tracking phase. This was shown by confining the view of the moving target to one eye, while permitting both eyes to be exposed to background stimulation during tracking. After such stimulation the magnitude of the aftereffect was equal in the two eyes.

scholarly journals On the respiration of the leaves of plants

1843 ◽  
Vol 4 ◽  
pp. 466-466
Keyword(s):  
Natural Condition ◽  
Carbonic Acid ◽  
Pure Water ◽  
Atmospheric Air ◽  
Acid Gas ◽  
Series Of Experiments ◽  
As If

The author gives an account of a series of experiments on the products of the respiration of plants, and more particularly of the leaves; selecting, with this view, specimens of plants which had been previously habituated to respire constantly under an inclosure of glass; and employing, for that purpose, the apparatus which he had formerly used in experimenting on the combustion of the diamond, and consisting of two mercurial gasometers, with the addition of two hemispheres of glass closely joined together at their bases, so as to form an air-tight globular receptacle for the plant subjected to experiment. The general conclusions he deduces from his numerous experiments conducted during several years, are, first, that in leaves which are in a state of vigorous health, vegetation is always operating to restore the surrounding atmospheric air to its natural condition, by the absorption of carbonic acid and the disengagement of oxygenous gas: that this action is promoted by the influence of light, but that it continues to be exerted, although more slowly, even in the dark. Secondly, that carbonic acid is never disengaged during the healthy condition of the leaf. Thirdly, that the fluid so abundantly exhaled by plants in their vegetation is pure water, and contains no trace of carbonic acid. Fourthly, that the first portions of carbonic acid gas contained in an artificial atmosphere, are taken up with more avidity by plants than the remaining portions; as if their appetite for that pabulum had diminished by satiety.

Distributed spatial coding in the superior colliculus: A review

1991 ◽  
Vol 6 (1) ◽  
pp. 3-13 ◽  
Author(s):  
James T. McIlwain
Keyword(s):  
Eye Movements ◽  
Superior Colliculus ◽  
Receptive Fields ◽  
Saccadic Eye Movements ◽  
Visual Direction ◽  
Saccade Amplitude ◽  
Spatial Coding ◽  
Distributed Coding

AbstractThis paper reviews evidence that the superior colliculus (SC) of the midbrain represents visual direction and certain aspects of saccadic eye movements in the distribution of activity across a population of cells. Accurate and precise eye movements appear to be mediated, in part at least, by cells of the SC that have large sensory receptive fields and/or discharge in association with a range of saccades. This implies that visual points or saccade targets are represented by patches rather than points of activity in the SC. Perturbation of the pattern of collicular discharge by focal inactivation modifies saccade amplitude and direction in a way consistent with distributed coding. Several models have been advanced to explain how such a code might be implemented in the colliculus. Evidence related to these hypotheses is examined and continuing uncertainties are identified.

scholarly journals Eye-hand coordination during flexible manual interception of an abruptly appearing, moving target

2018 ◽  
Vol 119 (1) ◽  
pp. 221-234 ◽  
Author(s):  
Yuhui Li ◽  
Yong Wang ◽  
He Cui
Keyword(s):  
Eye Movements ◽  
Moving Objects ◽  
Reaction Times ◽  
Hand Movements ◽  
Moving Target ◽  
Target Displacement ◽  
Transmission Delays ◽  
Sensory Transmission ◽  
Hand Coordination ◽  
Different Levels

As a vital skill in an evolving world, interception of moving objects relies on accurate prediction of target motion. In natural circumstances, active gaze shifts often accompany hand movements when exploring targets of interest, but how eye and hand movements are coordinated during manual interception and their dependence on visual prediction remain unclear. Here, we trained gaze-unrestrained monkeys to manually intercept targets appearing at random locations and circularly moving with random speeds. We found that well-trained animals were able to intercept the targets with adequate compensation for both sensory transmission and motor delays. Before interception, the animals' gaze followed the targets with adequate compensation for the sensory delay, but not for extra target displacement during the eye movements. Both hand and eye movements were modulated by target kinematics, and their reaction times were correlated. Moreover, retinal errors and reaching errors were correlated across different stages of reach execution. Our results reveal eye-hand coordination during manual interception, yet the eye and hand movements may show different levels of prediction based on the task context. NEW & NOTEWORTHY Here we studied the eye-hand coordination of monkeys during flexible manual interception of a moving target. Eye movements were untrained and not explicitly associated with reward. We found that the initial saccades toward the moving target adequately compensated for sensory transmission delays, but not for extra target displacement, whereas the reaching arm movements fully compensated for sensorimotor delays, suggesting that the mode of eye-hand coordination strongly depends on behavioral context.

Optokinetic Responses of the Crab, Carcinus to a Single Moving Light

1966 ◽  
Vol 44 (2) ◽  
pp. 263-274
Author(s):  
G. A. HORRIDGE
Keyword(s):  
Eye Movements ◽  
Apparent Motion ◽  
Horizontal Plane ◽  
Continuous Light ◽  
Lower Percentage ◽  
Eye Position ◽  
Complete Darkness ◽  
Intermittent Light ◽  
Optokinetic Responses ◽  
Dark Room

1. A crab in an otherwise dark room will stabilize its eye position by reference to a single small light, so long as the illumination at the eye exceeds about 0.0003 lux. 2. The eye movements follow the movements of the light. 3. Responses to a light moving in a horizontal plane resemble those to a striped drum, but at lower percentage following. 4. Apparent motion is an effective stimulus; with intermittent light the response is reduced. If there is a period of complete darkness after the first light the subsequent movement, when the second light comes on, is slower for longer dark periods. 5. The crab learns, after some repetitions, to discriminate between a continuous light and an intermittent one, as shown by its eventually stabilizing them at different points on its retina.

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