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.     

Overshadowing and blocking of the orientation-contingent color aftereffect: Evidence for a conditioning mechanism

Orientation-contingent color aftereffects have been interpreted by nonassociative mechanisms (adaptation of neural units that are both color and orientation specific) and by associative mechanisms (conditioning resulting from the pairing of pattern and hue). To evaluate associative accounts, contingent aftereffects were induced by exposing subjects to compound chromatic grid patterns consisting of two component gratings: one was horizontal or vertical, and the other a left- or right-learning diagonal. The ability of a component grating to elicit a color aftereffect depended on the relative salience and the aftereffect training history of the grating components. That is, orientation-contingent color aftereffects, like other conditional responses, display overshadowing and blocking. The results suggest that conditioning contributes to these aftereffects.     

Mystery of the anti-McCollough effect

The McCollough Effect (ME) is a complex perceptual aftereffect that remains of interest half a century after its discovery. It is argued that a recently reported variant, dubbed the anti-McCollough effect, is not the reverse of the ME, with aftereffect colors in the same direction as the inducing stimuli. A red-horizontal stimulus leads to a reddish aftereffect not because of red-horizontal parings, but despite them. The anti-ME is a weak standard-direction ME produced by complementary afterimage colors (afterimage green with horizontal), rather than by environmental colors, first shown decades ago. It is not a new type of contingent aftereffect. The red-horizontal pair does not interfere with the afterimage green-horizontal pair it produces because a single color-orientation pairing provides more ambiguous input than does the standard two orientation-color pairings (red-horizontal, green-vertical) of the ME. It is also argued that not even one orientation-contingent color aftereffect is convincingly shown in the "anti"-ME, let alone, as has previously been suggested, two simultaneous orientation-contingent color aftereffects in opposite directions at different levels of the visual system, in which the higher-level effect suppresses the downstream effect from reaching consciousness. The "anti"-ME can be explained by existing theories of contingent aftereffects, including perceptual-learning theory.     

The associative basis of contingent color aftereffects.

According to a conditioning analysis of the orientation-contingent color aftereffect (McCollough effect, ME), orientation stimulus (grids) become associated with color. Contrary to this interpretation are reports that simple forms cannot be used to elicit illusory color and that the ME is not degraded by decreasing the grid-color correlation. The present results indicate: (a) Form stimuli can contingently elicit color aftereffects; (b) even a non-patterned stimulus--the lightness of a frame surrounding a colored area--can contingently elicit color aftereffects; (c) this frame lightness-contingent aftereffect, like the ME, persists for at least 24 hr; and (d) the frame lightness-contingent aftereffect can be used to demonstrate that correlational manipulations affect the ME, as they affect other types of conditional responses.     

Orientation constancy of the McCollough effect

Two different techniques were used to determine the orientation constancy of orientation-contingent color aftereffects, McCollough effects. The results from both investigations agree and indicate That the aftereffect fails to exhibit orientation constancy other than that which can be explained by ocular countertorsion. Thus, the retinal rather than phenomenal orientation of the adaptation stimuli appears to be the determinant of aftereffect orientation. In fact, it is concluded that the aftereffect can be used to accurately monitor torsional eye position over long periods of time.     

Text-contingent color aftereffects: A reexamination

Five experiments reexamined color aftereffects contingent on the semantic properties of text (Allan, Siegel, Collins, & MacQueen, 1989). The influence of different assessment techniques and the effect of eye movements and overlapping contour information on the induction of color aftereffects by word and nonword letter strings were determined. Experiment 1 showed that no aftereffect was found when a traditional method of assessing color aftereffects was used. Experiments 2 and 4 demonstrated color aftereffects forboth words and nonwords, but only when subjects fixated the same locus during induction and testing and only when assessed with the technique described by Allan et al. (1989). If, however, eye movements were made during induction, no color aftereffect was obtained (Experiment 3). Induction to nontext patterns with properties similar to those of text but with fewer overlapping contours resulted in a strong color aftereffect (Experiment 5). These results suggest that the color aftereffect contingent on text is very weak and is not dependent on semantic factors, but that it is a product of induction to local color and orientation information.     

Simple and contingent aftereffects of perceived duration in vision and audition

After repeated presentations of a long inspection tone (800 or 1,000 msec), a test tone of intermediate duration (600 msec) appeared shorter than it would otherwise appear. A short inspection tone (200 or 400 msec) tended to increase the apparent length of the intermediate test tone. Thus, a negative aftereffect of perceived auditory duration occurred, and a similar aftereffect occurred in the visual modality. These aftereffects, each involving a single sensory dimension, aresimple aftereffects. The following procedures producedcontingent aftereffects of perceived duration. A pair of lights, the first short and the second long, was presented repeatedly during an inspection period. When a pair of test lights of intermediate duration was then presented, the first member of the pair appeared longer in relation to the second. A similar aftereffect occurred in the auditory modality. In these latter aftereffects, the perceived duration of a test light or tone is contingent—dependent—on its temporal order, first or second, within a pair of test stimuli. An experiment designed to test the possibility of cross-modal transfer of contingent aftereffects between audition and vision found no significant cross-modal aftereffects.     

Orientation-specific luminance aftereffects

Prolonged viewing of bright vertical (horizontal) gratings alternating with dim horizontal (vertical) gratings generates negative brightness aftereffects that are contingent on the orientation of orthogonal test gratings. The effect is measured by a brightness cancellation technique, similar to the color cancellation technique used in measuring McCollough effects. Like the latter, brightness aftereffects appear to persist for long periods. The magnitude of these aftereffects is a positive monotonic function of the luminance difference between the inducing gratings, and it depends on the conditions of induction; monocular induction generates larger aftereffects than binocular induction does. The aftereffect transfers interocularly, although its magnitude in the contralateral eye is substantially attenuated; binocular measurement, following monocular induction, results in even smaller aftereffects. An attempt to understand these findings within the computational model of brightness perception developed by Grossberg and Mingolla (1985a, 1985b) is presented.     

Contrast and frequency competition for orientation-contingent color aftereffects

A “competition” paradigm was developed to examine separately the effects of pattern contrast and spatial frequency characteristics on the strength of orientation-contingent color aftereffects (McCollough effects). After adapting to alternately presented red/black and green/black square-wave gratings (one horizontal, one vertical), 11 subjects viewed seven different kinds of test patterns. Unlike Standard McCollough effect test stimuli, the present patterns had variable luminance profiles running both horizontally and vertically within each test pattern area. Forced choice responses were used to determine which aftereffect color (red or green) appeared, as characteristics of vertical and horizontal luminance profiles were varied separately among test stimulus types. We conclude that pattern contrast and human contrast sensitivity account for aftereffect colors in such stimuli. When contrast is taken into consideration, aftereffects are not predicted by similarity between adaptation and test pattern Fourier characteristics, nor are they predicted by the width, per se, of pattern elements.     

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.     

Contingent color aftereffects: Reassessing old conclusions

Although there is considerable evidence supporting an associative interpretation of contingent color aftereffects, there are data that appear inconsistent with this interpretation. New findings from seven experiments are presented indicating that, contrary to earlier claims, contingent color aftereffects are observed after induction with (1) single orthogonal black bars on colored backgrounds, (2) geometric forms, and (3) two orthogonal grids of the same color. The results of these experiments are relevant to an associative interpretation of contingent color aftereffects, as well as to assessing alternative interpretations of the phenomenon.     

Monocular-contingent and binocular-contingent aftereffects

Alternate monocular and binocular exposure to complementary stimulation can yield opposite but coexisting aftereffects that are contingent on whether the test display is viewed with one eye or two eyes. The motion aftereffect was studied by adapting each eye separately to a contracting spiral and both eyes together to an expanding spiral. The stationary test spiral subsequently appeared to be expanding when viewed monocularly, but to be contracting when it was seen with both eyes open. With respect to the McCollough effect, after monocular exposure to red-vertical and green-horizontal gratings and binocular exposure to red-horizontal and green-vertical gratings, the appearance of the color of the test gratings when viewed with one eye was different from that when viewed with both eyes. Opposite, coexisting aftereffects induced by complementary stimulation can be interpreted as evidence that there are unique binocular aspects to visual function.     

Color aftereffects contingent on perceptual organization

The present experiment demonstrated that (a) cognitive organizational factors influence an orientation-contingent color (McCollugh) aftereffect, and (b) adaptation to colored gratings affected the perceptual organization of a reversible figure. Following adaptation to colored gratings, color aftereffects were reported in only one of two organizations of a reversible figure, and the colors conformed to the subjective contours of the test pattern rather than exclusively to the regions defined by horizontal and vertical pattern elements. In addition, an organization of the reversible figure that segregated vertical and horizontal pattern elements was dominant subsequent to adaptation.     

The influence of imagery ability on color aftereffects produced by physically present and imagined induction stimuli

Two methods of induction were used to produce orientation-contingent color aftereffects for observers assigned to one of three groups (high, medium, and low) on the basis of self-rated imagery ability. In Experiment 1, observers were required to make magnitude estimates of color aftereffects following inspection of stimulus patterns normally used to produce McCollough effects (e.g., red vertical contours, green horizontal contours). Experiment 2 was a partial replication of Experiment 1, with additional induction conditions in which observers were required to imagine the presence of appropriately oriented contours when particular homogeneous color patches were presented. The results indicated that self-rated imagery ability was not a significant factor in differentiating between observers’ performance when orthodox induction procedures were used (Experiment 1). In addition, there were no reliable indications (Experiment 2) that imagined stimulus attributes can be effectively substituted for real stimulus attributes in order to produce orientation-contingent color aftereffects. The results are discussed in terms of their implications for the use of imagery-induced perceptual phenomena as a paradigm for investigating the possibility of common neural mechanisms in perception and imagination; in addition, the general implications of the results for understanding the functional significance of self-reported imagery ability are examined.     

Internally augmented displays: contingent aftereffects as performance aids

Previous research on visual contingent aftereffects has been concerned with examining the effects of various parameters (e.g., spatial frequency and luminance) on the adaptation to, and decay of, contingent aftereffects. The current study tested the viability of using visual contingent aftereffects in a display context. Using established characteristics of contingent aftereffects, a program of contingent aftereffect adaptation was designed. Studies were conducted to determine if subjects who were adapted to see visual contingent aftereffects invoked by a visual display could achieve more rapid or certain identification of a display under low luminance conditions. The results confirmed (a) that contingent aftereffects can improve performance on a visual discrimination task requiring information from a display and (b) that contingent aftereffects are more enhanced at low levels of illumination.     

Color aftereffect contingent on text

During adaptation, two different letter strings (each five or six letters) were presented to subjects alternately, one in green and the other in magenta. The extent to which these letter strings subsequently elicited a color aftereffect was assessed. In different experiments, the chromatic letter strings consisted of words and nonwords. The results indicated that letter strings that form English words can contingently elicit a color aftereffect. This was the case even when the words were anagrams. There was no evidence that nonword letter strings could contingently elicit such an aftereffect, even when the nonwords conformed to English orthography. The results are relevant to understanding other contingent color aftereffects (McCollough effects), illusory color noted by computer operators who work at monochrome (green or amber) displays, and the processing of text.     

Visual aftereffect of texture density contingent on color of frame

An aftereffect of perceived texture density contingent on the color of a surrounding region is reported. In a series of experiments, participants were adapted, with fixation, to stimuli in which the relative density of two achromatic texture regions was perfectly correlated with the color presented in a surrounding region. Following adaptation, the perceived relative density of the two regions was contingent on the color of the surrounding region or of the texture elements themselves. For example, if high density on the left was correlated with a blue surround during adaptation (and high density on the right with a yellow surround), then in order for the left and right textures to appear equal in the assessment phase, denser texture was required on the left in the presence of a blue surround (and denser texture on the right in the context of a yellow surround). Contingent aftereffects were found (1) with black-and-white scatter-dot textures, (2) with luminance-balanced textures, and (3) when the texture elements, rather than the surrounds, were colored during assessment. Effect size was decreased when the elements themselves were colored, but also when spatial subportions of the surround were used for the presentation of color. The effect may be mediated by retinal color spreading (Pöppel, 1986) and appears consistent with a local associative account of contingent aftereffects, such as Barlow’s (1990) model of modifiable inhibition.     

Contingent aftereffects: lateral interactions between color and motion

A randomly dotted yellow disk was rotated at a speed of 5 rpm, alternating in direction every 10 sec. Its change in direction of rotation was paired with a change in surround color, which was either red or green. After 15 min of exposure, observers reported vivid motion aftereffects contingent on the color of both the stationary disk and the surround, even though during adaptation only motion or color was associated with either alone. In further experiments, it was established that a change in color (or direction of motion) of the disk could be associated with a change in direction of motion (or color) of the surround. Such lateral effects were found even when a wide (5 degree) annulus was introduced between the disk and the surround during adaptation and testing. Furthermore, the aftereffects generalized to the annulus, which was not associated with either color or motion during adaptation. However, when the disk alone was adapted to color and motion, no generalization to the surround was found (and vice versa), suggesting that the effects are not produced by adaptation of large receptive fields or by scatter of light within the eye. The results appear to conflict with the ideas that contingent aftereffects are confined to the adapted area of the retina and that they are built up by links between single-duty neurones, and with an extreme view of the segregation of color and motion early in human vision.     

Buildup and decay of a three-dimensional rotational aftereffect obtained with a three-dimensional figure

Gaps in past literature have raised questions regarding the kinds of stimuli that can lead to three-dimensional (3-D) rotation aftereffects. Further, the characteristics of the buildup and decay of such aftereffects are not clear. In the present experiments, rotation aftereffects were generated by projections of cube-like stimuli whose dynamic perspective motions gave rise to the perception of rotation in unambiguous directions; test stimuli consisted of similar cubes whose rotation directions were ambiguous. In experiment 1, the duration of the adaptation stimulus was varied and it was found that the 3-D rotation aftereffect develops with a time constant of approximately 26 s. In experiment 2, the duration between adaptation and testing was varied. It was found that the 3-D rotation aftereffect has a decay constant of about 9 s, similar to that observed with 2-D motion aftereffects. Experiment 3 showed that the rotation aftereffects were not simple depth aftereffects. To account for these aftereffects and related data, a modification of an existing neural-network model is suggested.     

Visual motion influences the contingent auditory motion aftereffect

In this study, we show that the contingent auditory motion aftereffect is strongly influenced by visual motion information. During an induction phase, participants listened to rightward-moving sounds with falling pitch alternated with leftward-moving sounds with rising pitch (or vice versa). Auditory aftereffects (i.e., a shift in the psychometric function for unimodal auditory motion perception) were bigger when a visual stimulus moved in the same direction as the sound than when no visual stimulus was presented. When the visual stimulus moved in the opposite direction, aftereffects were reversed and thus became contingent upon visual motion. When visual motion was combined with a stationary sound, no aftereffect was observed. These findings indicate that there are strong perceptual links between the visual and auditory motion-processing systems.