Producing the effect
To obtain the effect, first look at a test image similar to below on the left. It contains oppositely oriented gratings of lines.. Next, stare alternately at two induction images shown on the right below. One image should show one orientation of grating (here horizontal) with a colored background (red) and the other should show the other orientation of grating (here vertical) with a different, preferably oppositely colored background (green). Each image should be gazed at for several seconds at a time, and the two images should be gazed at for a total of several minutes for the effect to become visible. Stare approximately at the center of each image, allowing the eyes to move around a little. After several minutes, look back to the test image; the gratings should appear tinted by the opposite color to that of the induction gratings (i.e., horizontal should appear greenish and vertical pinkish).
Properties of the effect
The McCollough effect is remarkable because it is long-lasting. McCollough originally reported that these aftereffects may last for an hour or more. They can last much longer than that, however. Jones and Holding (1975) found that 15 minutes of induction can lead to an effect lasting 3 months.
The effect is different from colored afterimages, which appear superimposed on whatever is seen and which are quite brief. It depends on retinal orientation (tilting the head by 45 degrees makes the colors in the above example disappear; tilting the head by 90 degrees makes the colors reappear such that the gravitationally vertical grating now looks green), and because inducing the effect with one eye leads to no effect being seen with the other eye. However, there is some evidence of binocular interactions.
Any aftereffect requires a period of induction (or adaptation) with an induction stimulus (or, in the case of the McCollough effect, induction stimuli). It then requires a test stimulus on which the aftereffect can be seen. In the McCollough effect as described above, the induction stimuli are the red horizontal grating and the green vertical grating. A typical test stimulus might show adjacent patches of black-and-white vertical and horizontal gratings (as above). The McCollough-effect colors are less saturated than the induction colors.
The induction stimuli can have any different colors. The effect is strongest, however, when the colors are complementary, such as red and green, and blue and orange. A related version of the McCollough effect also occurs with a single color and orientation. For example, induction with only a red horizontal grating makes a black-and-white horizontal test grating appear greenish whereas a black-and-white vertical test grating appears colorless (although there is some argument about that). Stromeyer (1978) called these non-redundant effects. According to him, the classic effect with induction from two different orientations and colors simply makes the illusory colors more noticeable via contrast.
The effect is specific to the region of the retina that is exposed to the induction stimuli. This has been shown by inducing opposite effects in adjacent regions of the retina (i.e., from one region of the retina verticals appear pink and horizontals appear greenish; from an adjacent region of the retina, verticals appear greenish and horizontals appear pink). Nevertheless, if a small region of the retina is exposed to the induction stimuli, and the test contours run through this region, the effect spreads along those test contours. Of course, if the induced area is in the fovea (central vision) and the eyes are allowed to move, then the effect will appear everywhere in the visual scene visited by the fovea.
The effect is also optimal when the thickness of the bars in the induction stimulus matches that of those in the test stimulus (i.e., the effect is tuned, albeit broadly, to spatial frequency). This property led to non-redundant effects being reported by people who had used computer monitors with uniformly colored phosphors to do word processing. These monitors were popular in the 1980s, and commonly showed text as green on black. People noticed later when reading text of the same spatial frequency, in a book say, that it looked pink. Also a horizontal grating of the same spatial frequency as the horizontal lines of the induction text (such as the horizontal stripes on the letters "IBM" on the envelope for early floppy disks) looked pink.
A variety of similar aftereffects have been discovered not only between pattern and color contingencies, but between movement/color, spatial frequency/color and other relationships. All such effects may be referred to as McCollough Effects or MEs.
Explanations of the effect
McCollough's paper sparked hundreds of scientific papers on the effect.
Explanations of the McCollough effect appear to fall in to three camps. McCollough indicated color adaptation of edge sensitive neurons in lower, monocular regions of the visual cortex.
A functional explanation of MEs has been posited in the form of an error-correcting device (ECD) whose purpose is to maintain an accurate internal representation of the external world. Consistent pairings of color and oriented lines are not found frequently in natural environments, thus consistent pairing may indicate pathology of the eye. An ECD might compensate for such pathology by adjusting the appropriate neurons to a neutral point in adaptation to orientation contingent color.
A third explanation points to the contribution of classical conditioning to normal homeostatic regulation. MEs are explained by the same mechanisms as pharmacological withdrawal symptoms, thus the "pharmacological CR is expressed as pharmacological adaptation (tolerance) in the presence of the drug, and withdrawal symptoms in the absence of the drug" and the "chromatic CR is expressed as chromatic adaptation in the presence of colour, and the ME in the absence of colour". By this account MEs are of no adaptive value, but have been selected for as a domain-general ability to anticipate events. This is related to opponent-process theory.
It is worth noting that these theories do not predict or explain the anti-McCollough effect.
Neurophysiological explanations of the effect have variously pointed to the adaptation of cells in the lateral geniculate nucleus designed to correct for chromatic aberration of the eye, to adaptation of cells in the visual cortex jointly responsive to color and orientation (this was McCollough's explanation) such as monocular areas of cortical hypercolumns, to processing within higher centers of the brain (including the frontal lobes), and to learning and memory. In 2006, the explanation of the effect was still the subject of debate, although there was a consensus in favor of McCollough's original explanation.
MEs do not transfer interocularly and from this it seems reasonable to deduce that the effect occurs in an area of the visual system prior to V1-4B, where binocular cells first occur.
The anti-McCollough effect
Recently, a new effect in the opposite direction of the McCollough effect was discovered and has been termed the anti-McCollough effect. This effect may be induced by alternating pairings of gratings in parallel alignment, one achromatic (black and white) and the other black and a single color (say black and red). If the color used was red, then after the induction phase the achromatic grating appeared slightly red. This effect is distinct from the classical effect in three important regards; the perceived color of the aftereffect is the same as the inducer's color, the perceived color of the aftereffect is weaker than the classical effect, and the aftereffect shows complete interocular transfer. Like the classic effect, the anti-McCollough effect (AME) is long lasting. Despite producing a less saturated illusory color, the induction of an AME may override a previously induced ME.
Given that AMEs do transfer interocularly, it is reasonable to suppose that they must occur in higher, binocular regions of the brain. Despite producing a less saturated illusory color, the induction of an AME may override a previously induced ME, providing additional weight to the argument that AMEs occur in the higher visual areas than MEs.
Explanations of the effect by adaptation of edge-detectors, functional ECDs, and classical conditioning are compelling but may have to be adjusted for the inclusion of AMEs, if the AME can be shown to replicate by independent labs.
The development of increasingly accurate representation of the visual appearances of things has a long history in art. It includes elements such as the accurate depiction of the anatomy of humans and animals, of perspective and effects of distance, and of detailed effects of light and colour. The Art of the Upper Paleolithic in Europe achieved remarkably lifelike depictions of animals, and Ancient Egyptian art developed conventions involving both stylization and idealization that nevertheless allowed very effective depictions to be produced very widely and consistently. Ancient Greek art is commonly recognised as having made great progress in the representation of anatomy, and has remained an influential model ever since. No original works on panels or walls by the great Greek painters survive, but from literary accounts, and the surviving corpus of derivative works (mostly Graeco-Roman works in mosaic) it is clear that illusionism was highly valued in painting. Pliny the Elder's famous story of birds pecking at grapes painted by Zeuxis in the 5th century BC may well be a legend, but indicates the aspiration of Greek painting. As well as accuracy in shape, light and colour, Roman paintings show an unscientific but effective knowledge of representing distant objects smaller than closer ones, and representing regular geometric forms such as the roof and walls of a room with perspective. This progress in illusionistic effects in no way meant a rejection of idealism; statues of Greek gods and heroes attempt to represent with accuracy idealized and beautiful forms, though other works, such as heads of the famously ugly Socrates, were allowed to fall below these ideal standards of beauty. Roman portraiture, when not under too much Greek influence, shows a greater commitment to a truthful depiction of its subjects.
Bas-de-page of the Baptism of Christ, "Hand G" (Jan van Eyck?), Turin-Milan Hours. An advanced illusionistic work for c 1425, with the dove of the Holy Ghost in the sky.
The art of Late Antiquity famously rejected illusionism for expressive force, a change already well underway by the time Christianity began to affect the art of the elite. In the West classical standards of illusionism did not begin to be reached again until the Late medieval or Early Renaissance period, and were helped by the development of new techniques of oil painting which allowed very subtle and precise effects of light to be painted using very small brushes and several layers of paint and glaze. Scientific methods of representing perspective were developed in Italy and gradually spread across Europe, and accuracy in anatomy rediscovered under the influence of classical art. As in classical times, idealism remained the norm.
The accurate depiction of landscape in painting had also been developing in Early Netherlandish and Renaissance painting, and was then brought to a very high level in 17th century Dutch Golden Age painting, with very subtle techniques for depicting a range of weather conditions and degrees of natural light. After being another development of Early Netherlandish painting, by 1600 European portraiture could give a very good likeness in both painting and sculpture, though the subjects were often idealized by smoothing features or giving them an artificial pose. Still life paintings, and still life elements in other works, played a considerable role in developing illusionistic painting, though in the Netherlandish tradition of flower painting they long lacked "realism", in that flowers from all seasons were typically used, either from the habit of assembling compositions from individual drawings, or as a deliberate convention; the large displays of bouquets in vases, though close to modern displays of cut flowers that they have influenced, were entirely atypical of 17th century habits, where flowers were displayed one at a time. Intriguingly, having led the development of illusionic painting, still life was to be equally significant in its abandonment in Cubism.
In his writings and art criticisms during the mid-1960s art critic/artist Donald Judd claimed that illusionism in painting undermined the artform itself. Judd implied that painting was dead, claiming painting was a lie and because it depicted the illusion of 3-dimensions on a flat surface. Judd claimed that painting needed to recognize its objecthood in real space and reject illusion. Donald Judd wrote in “Specific Objects” in 1965:
Three dimensions are real space. That gets rid of the problem of illusionism and of literal space, space in and around marks of color… Actual space is intrinsically more powerful and specific than paint on a flat surface.
The Wonderful World of Patrick Hughes
Patrick Hughes (born 20 October 1939) is a British artist working in London. He is the creator of “reverspective”, an optical illusion on a 3-dimensional surface where the parts of the picture which seem farthest away are actually physically the nearest.
His first “reverse perspective” or “reverspective” was Sticking Out Room(1964), which was a life-size room for the Institute of Contemporary Arts (ICA) in 1970. He returned to explore the possibilities of reverspective in 1990 with Up the Line and Down the Road (1991) Since then, his reverspectives have been shown in London, New York, Santa Monica, Seoul, Chicago, Munich and Toronto.
He explains reverspective:
‘Reverspectives are three-dimensional paintings that when viewed from the front initially give the impression of viewing a painted flat surface that shows a perspective view. However as soon as the viewer moves their head even slightly the three dimensional surface that supports the perspective view accentuates the depth of the image and accelerates the shifting perspective far more than the brain normally allows. This provides a powerful and often disorienting impression of depth and movement. The illusion is made possible by painting the view in reverse to the relief of the surface, that is, the bits that stick farthest out from the painting are painted with the most distant part of the scene’
The picture surface of Vanishing Venice (above) is 3-dimensional, made of two pyramids protruding towards the viewer with the tops cut off: the bases of the pyramids are farthest away (flat against the wall). The two lighter rectangles which appear to be in the distance at the end of the buildings are the flat tops and thus the part of the image physically nearest to the viewer (see diagram below).
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