Color-selective tilt aftereffects with subjective contours

Displays yielding edges visible at sites where the visual stimulus was homogeneous (subjective contours) as well as with edges defined by spatial discontinuities in luminance (real contours) were used to induce the tilt aftereffect. Under monoptic conditions, the aftereffect was larger when the inspection and test edges were shown in the same colored light than when they were shown in different colored lights. Under dichoptic conditions (display of inspection edges to one eye and test edges to the other eye), the aftereffect was reduced in size and it was no longer selective to the color relationship between the inspection and test stimuli. Similar results were obtained with subjective and real contours. In the recent literature, subjective contours have been treated as products of cognitive and inferential operations, whereas neural edge detectors have been implicated in the perception of real contours. The present data suggest, however, the need for caution in attributing the perception of real and subjective contours to fundamentally different processes.     

Color-selectivity in simultaneous motion contrast

Thirty-two Ss were required to estimate the apparent motion of stationary vertical lines viewed against a background of moving vertical lines when both patterns were seen by the same eye (monoptic conditions) or the center pattern was seen by one eye and the surrounds by the other eye (dichoptic conditions). The stationary lines appeared to be moving from right to left as the surrounds moved left to right. The simultaneous motion contrast found under monoptic conditions was maximal when the center pattern and the surrounds were the same color and was reduced when they differed in color. The surrounds had limited influence on the apparent motion of the center section under dichoptic condition, and the color relationship was no longer important. Related color selectivity has been reported for the motion aftereffect (successive motion contrast), and both sets of data can be attributed to inlaibitory interaction (simultaneous in one case and successive in the other) among neural detectors tuned to wavelength as well as the direction of image motion.     

Latency differences in monoptic and dichoptic shape and color decision making

Past research based on the McCollough effect and efficacy of chromatic cues in stereopsis suggests that color information is difficult to process binocularly as compared to form information. This study evaluates this proposition using a reaction time paradigm. Subjects decided whether two simultaneous visual stimuli were the same in shape or color. With presentation to the same eye, color reaction times led shape latencies. Presenting one target to one eye and one to the other slowed color times. Delaying one target by 500 msec yielded dichoptic and monoptic color decisions faster than shape. The results are related to the relationships of color and contrast pathways and possible differences in binocular rivalry.     

The attentional dynamics of masked detection

A dichoptic masking procedure was used to test whether the mask-dependent cuing effects found in luminance detection by P. L. Smith (2000a) were due to integration masking or interruption masking. Attentional cuing enhanced detection sensitivity (d') when stimuli were backwardly masked with either dichoptic or monoptic masks, whereas no cuing effect was found with unmasked stimuli, implying the mask dependencies were due to interruption of stimulus processing in visual cortex by the mask. The effect is predicted by a gated diffusion process model in which masks interrupt stimulus processing and attention controls the flow of information to a sequential-sampling decision mechanism. The model correctly predicts different patterns of performance for detection and discrimination and cuing effects in simple reaction time.     

Absence of color-selectivity in Duncker-type induced visual movement

Using a stationary target and moving field, both consisting of gratings of vertical light and dark bars, Over and Lovegrove (1973) reported that, with monoptic viewing, induced target movement is weaker when the light bars of the two components are different in color. This reduction did not occur for dichoptic viewing, for which the aftereffect was almost negligible. Six experiments are described. The effect of different colors was not confirmed, using a stationary point and moving frame or stationary and moving gratings. Reduced effects for different colors and greatly reduced effects for dichoptic viewing occurred only when there was a stationary boundary to the moving bars of the field grating, as in Over and Lovegrove’s experiment. It is concluded that the effect studied by Over and Lovegrove is not the classical induced movement described by Duncker (1929/1938) but one due to periodic coincidence and noncoincidence of moving and stationary bars in grating patterns. This effect is absent when target and field bars are rendered more distinguishable by different colors.     

Absence of binocular interaction between spatial and color attributes of visual stimuli

The hypothesis that induction of the McCollough effect (spatially selective color aftereffects) entails adaptation of monocularly driven detectors tuned to both spatial and color attributes of the visual stimulus was examined in four experiments. The McCollough effect could not be generated by displaying contour information to one eye and color information to the other eye during inspection, even in the absence of binocular rivalry. Nor was it possible to induce depth-specific color aftereffects following an inspection period during which random-dot stereograms were viewed, with crossed and uncrossed disparity seen in different colored light. Masking and aftereffect in the perception of stereoscopic depth were also nonselective to color; in both cases, perceptual distortion was controlled by stereospatial variables but not by the color relationship between the inspection and test stimuli. The results suggest that binocularly driven spatial detectors in human vision are insensitive to wavelength.     

Dichoptic induction of movement aftereffects contingent on color and on orientation

Some comparative experiments on the dichoptic induction of the movement aftereffect (MAE) contingent on color and the MAE contingent on orientation are reported. Colorcontingent movement aftereffects could be evoked only when the eye which had viewed color during adaptation also viewed color during test sessions. When the apparent color of the test field was changed by binocular color rivalry, contingent movement aftereffects (CMAEs) appropriate to the suppressed color were reported. After dichoptic induction of the orientation-contingent MAE, aftereffects could be obtained whether the eliciting gratings and stationary test fields were presented together to either eye alone or were dichoptically viewed.     

Potential artifact in dichoptic backward masking.

Under some conditions a dark interval in the target eye may be concomitant with presentation of a dichoptic mask. Results show that this monoptic dark interval contributes to the over-all observed dichoptic masking effect.     

Induction of the McCollough effect II: Two different mechanisms

An orientation-specific chromatic aftereffect was observed when a single colored grating was used as an induction stimulus. The magnitude of the aftereffect was compared to that obtained when alternating orthogonal gratings in complementary hues were used as induction stimuli. The two-stimulus condition produced a stronger aftereffect than a single-stimulus condition. This facilitation was also obtained when a colored plain square with no grating was substituted for the second colored grating in the two-stimulus condition. The results suggest that the McCollough effect involves adaptation of two different mechanisms, one which is orientation-specific and one which is not.     

Perceptual masking: Peripheral vs central factors

Perceptual masking was studied under binocular and dichoptic conditions in order to separate peripheral and central interference effects. Under binocular conditions, when the test flash (TF) and the blanking flash (BF) fell on both retinas, both retroactive and proactive masking were demonstrated. Under dichoptic conditions, when the TF fell on one eye and the BF on the other eye, thus eliminating opportunity for intraretinal interference, there was partial retroactive perceptual masking and no proactive masking. These results suggest that binocular proactive masking is due to peripheral light adaptation, that binocular retroactive masking is due to both peripheral and central effects, and that dichoptic masking is due solely to central retrochiasmal interference. It is proposed that dichoptic retroactive perceptual masking affords a method of investigating central perception time, i.e., the time to consolidate a perceptual experience.     

Presence and absence of color selectivity in the motion aftereffect

It is controversial whether the magnitude of the motion aftereffect is greater when both inspection and test stimuli are the same color rather than different colors (color selectivity). The present experiments show that the extent of color selectivity in the classical motion aftereffect depends upon (1) the duration of the interval between inspection and test, and (2) the nature of the stimulation during this interval. These findings are consistent with previous reports of two phases in the motion aftereffect and are interpreted in terms of the known properties of sustained and transient cells in the human visual system.     

Checkerboard-specific color aftereffects: A failure to find effects of perceptual organization

Two experiments investigated the effects of differing perceptual organizations of reversible figures on McCollough aftereffects. Experiment 1 used colored checkerboard inducing stimuli and achromatic grating test stimuli. While some subjects tended to organize the checkerboards into rows and/or columns and others to organize them into obliques, these variations did not result in differences in aftereffect direction or magnitude. Experiment 2 induced an aftereffect with colored gratings and tested with checkerboards, gratings, and a reversible concentric octagon pattern. Perceptual organization had no effect on results for checkerboards, but was related to aftereffect strength for the octagon pattern. Indirect evidence suggests that, in the latter case, differences in aftereffect strength may have influenced the perceived organization, rather than vice versa. Finally, regardless of the specific organization perceived, spontaneous viewing of all test stimuli produced stronger aftereffects than were found when subjects reorganized the pattern. This may have resulted from a viewing strategy associated with reorganization, since similarly small aftereffects were found when subjects concentrated their attention on a single pattern element.     

Establishment and decay of orientation-contingent aftereffects of color

We have used a null method to measure the orientation-contingent aftereffects of color first described by McCollough. After alternately inspecting, for example, a green horizontal line grating and a magenta vertical line grating, the Os report that in achromatic test gratings the horizontal lines appear pinkish and the vertical lines appear greenish. We have used a special color-mixing projector to add variable amounts of green and magenta light to the test gratings until they appear matched and nearly achromatic. The colorimetric purity needed to achieve this null setting is a quantitative measure of the strength of the colored aftereffect. Following inspections of the colored patterns ranging from 15 sec to 150 min, six Os showed aftereffects lasting from a few minutes to 7 or more days. The indices of colorimetric purity increase with inspection time and decline with time after inspection. The decay function is not quite linear either on semilog or on log-log coordinates. The rate of decay is mainly dependent on the magnitude of the effect built up during inspection. We conclude that the buildup and decay of these aftereffects show some of the time characteristics usually associated with central adaptability rather than sensory adaptation.     

Developmental aspects of dichoptic viewing

Age-related performance changes on a dichoptic viewing task were examined with twenty-five (25) individuals in a cross-sectional design. Using a double-report procedure, subjects were asked to identify two different consonant-vowel graphemes presented separately to the same foveal area of each eye (i.e., dichoptic stimulation). Stimuli were presented at stimulus-onset asynchronies (SOAs) ranging from 0 to 300 msec in 50-msec steps. Results indicated that the number of both-correct trials (i.e., correct reports of both stimuli in a dichoptic pair) significantly increased with age, while single-correct trials (a correct report of only one stimulus in the pair) significantly decreased with age. In addition, the shape of the masking functions indicated lagging stimuli were reported more accurately than leading stimuli at SOAs of 50–300 msec for all subjects. Younger subjects exhibited peak masking effects for synchronous presentations (0-msec SOA) while older individuals showed peak masking at SOAs of 50 msec. Results suggest developmental performance changes noted in processing visual information parallel, to a remarkable degree, those observed in processing auditory information.     

Aftereffects in binocular rivalry

Five experiments are reported in which the aftereffect paradigm was applied to binocular rivalry. In the first three experiments rivalry was between a vertical grating presented to the left eye and a horizontal grating presented to the right eye. In the fourth experiment the rivalry stimuli consisted of a rotating sectored disc presented to the left eye and a static concentric circular pattern presented to the right. In experiment 5 rivalry was between static radiating and circular patterns. The predominance durations were systematically influenced by direct (same eye) and indirect (interocular) adaptation in a manner similar to that seen for spatial aftereffects. Binocular adaptation produced an aftereffect that was significantly smaller than the direct aftereffect, but not significantly different from the indirect one. A model is developed to account for the results; it involves two levels of binocular interaction in addition to monocular channels. It is suggested that the site of spatial aftereffects is the same as that for binocular rivalry, rather than sequentially prior.     

Effects of test-mask similarity on forward and backward masking of patterns by patterns

Summary Effects of test-mask similarity on the masking function were examined in two experiments. In Experiment 1, random bar patterns were used as test and mask stimuli. Bars were oriented in 135° oblique direction in test stimuli, and in 135° or 45° oblique direction in mask stimuli. The SOA was varied from 0 to 100 ms (backward masking). In Experiment 2, red and blue random dot patterns were used as both test and mask stimuli, with SOAs of –100 to 100 ms (forward and backward masking). The subject was asked to report the number of bars or dots as quickly as possible. The results of four subjects in one experiment and five in the other indicated that masking effects were generally greater when the test and mask stimuli were the same in orientation or color than when they were different. Slightly asymmetrical U-shaped functions were obtained both in the same and in different (orientation or color) conditions. A two-factor model with a similarity-related symmetrical integration process and a similarity-unrelated asymmetrical interuption process was considered.Experiment 1 was conducted by the first and third authors at Chiba University, and Experiment 2 was performed by the first and second authors at the University of Tokyo     

Orientation-specific aftereffects and illusions in the perception of brightness

Orientation-specific brightness aftereffects were found when vertical and horizontal gratings of the same space-average luminance were viewed following alternate exposure to vertical and horizontal gratings that differed in space-average luminance. The vertical test grating appeared bright following exposure to a dim vertical grating, and dim after a bright vertical grating had been viewed. This aftereffect did not occur when the adaptation gratings had been seen by one eye and the test gratings by the other eye. An orientation-specific illusion in the perception of brightness was also found, with the white sectors of a vertical grating appearing brighter against a background of horizontal lines than they did against a background of vertical lines. Both distortions imply that there are detectors in the human visual system that are conjointly tuned to luminance and contour orientation.     

Colored aftereffects produced with moving edges

Colored aftereffects that lasted as long as 6 weeks were produced with moving patterns of parallel black and white stripes or with black and white spirals. During adaptation, the patterns moved periodically in opposite directions, each direction paired with one illuminant, red or green. When the moving patterns were later viewed in white light, S saw the red and green colors, but they were related in the opposite way to the direction of motion. The red and green aftereffects were also produced by other pairs of illuminants, red and white, white and green, reddish-yellow and white, and white and greenish-yellow. The aftereffects did not occur unless, during adaptation, the stripes moved in both directions, each direction paired with a different color. The aftereffect was elicited by stripe motion over the retina—it was seen when the eye swept over a pattern of stationary stripes. The aftereffect desaturated when the retinal orientation of the stripes was changed from the adaptation orientation. Saturation was increased by longer exposure and slower speed during adaptation and by faster speed and a more rapid rate of altemation during the test. The luminance of the adaptation light seemed to have little effect. The aftereffect did not transfer from one eye to the other, and it did not change retinal locus, as was shown when clear images of a colored square that lasted several days were produced with a spiral. S ftxated the spiral’s center. The spiral rotated altemately in opposite directions. A red square with a green surround was projected on the center of the spiral when it rotated in one direction; a green square with a red surround was used when it rotated in the other direction. Following 50 min of adaptation, colored images of the squares were seen when the center of the spiral was ftxated and the direction of     

Variation in hue of a contour-contingent aftereffect due to color adaptation during inspection of the stimulus patterns

The McCollough Effect (a colored line-orientation-contingent aftereffect) has been attributed to the presence of edge detectors specific to wavelength in the human visual system. The present study tests this hypothesis by introducing unlined colored fields into the inspection condition and by comparing the subsequent aftereffect with the aftereffect induced by the inspection condition not including the unlined colored fields. The data indicate that the hues of the aftereffects differ, suggesting that the color and line stimuli may be processed by different populations of neural elements, and that the color-coded edge detector model is not adequate to account for the observations.     

Spatial-frequency masking with briefly pulsed patterns

Spatial-frequency masking was studied with briefly pulsed (25 ms) vertical gratings. The mask was a noise grating, and the test pattern was a sinusoidal grating. A low-frequency band of noise masked a low- but not high-spatial-frequency test grating when the patterns were presented simultaneously. A high-frequency band of noise did not mask a low-frequency test grating when the patterns were presented simultaneously or when the mask was presented after the test pattern (backward masking). Masking was, however, observed when the mask or test pattern was of sufficiently high contrast so that the stimuli had nonlinear distortion and thus produced DC shifts of the field luminance.