The Cornsweet illusion, also known as the Craik–O'Brien–Cornsweet illusion or the Craik–Cornsweet illusion, is an optical illusion that was described in detail by Tom Cornsweet in the late 1960s.[1]Kenneth Craik and Vivian O'Brien had made earlier observations in a similar vein.[2]
In an example of the Cornsweet illusion, the whole left half of this rectangle seems to be lighter than the right. In fact they have the same brightness, apart from the gradients in the center.The same image as above, but the edge in the middle is hidden: the left and right part of the image appear as the same color.
The original version of the illusion involved a rapidly spinning black-and-white disk, painted in a way that would create the appearance of a gradient effect when in motion.[3] An equivalent static version of illusion is composed of a gray rectangle where the left half fades to a lighter shade as it approaches a vertical center line, and the right half fades to a darker gray approaching the same line. As a result, the whole left half of the rectangle appears lighter than the right half, but in fact the brightness of both areas is exactly the same. This can be seen by blacking out the region containing the edge.
This phenomenon is similar to the phenomenon of simultaneous contrast and Mach bands, but differs from it in two important respects.
In Mach bands, the effect is seen only on areas that are close to the intensity gradient. In the Craik–O'Brien–Cornsweet illusion, a very small area (the central "edge") affects the perception of entire large areas, portions of which are distant from the edge.
In the Cornsweet illusion, the region adjacent to the light part of the edge appears lighter, and the region adjacent to the dark part of the edge appears darker, just the opposite of the usual contrast effects.
The actual distribution of luminance in the picture, and the typical perception of luminance.
A far more convincing and dramatic version of the effect can be seen in the article by Purves, Lotto, and Nundy,[4] where it is presented within a quasi-realistic image of solid, illuminated objects.[5] These writers give an explanation of this and other illusions, in which the visual system and brain are posited to generate percepts on an empirical basis that is much like a reflex. In their words, "... [perception] accords not with the features of the retinal stimulus or the properties of the underlying objects, but with what the same or similar stimuli have typically signified in the past."[citation needed]
Referencesedit
^Cornsweet T (1970) Visual Perception. New York: Academic Press.
^Colman, Andrew M. (2015), "Craik–O'Brien effect", A Dictionary of Psychology (4th ed.), Oxford University Press, pp. 175–176, ISBN9780191057847
^Lotto, R. Beau. "The Cornsweet Illusion, Figure 2". researchgate.net. Retrieved 4 November 2021.
^Purves D., Lotto R.B., Nundy S. (2002) Why We See What We Do, American Scientist 90(3):236-243.
cornsweet, illusion, also, known, craik, brien, craik, optical, illusion, that, described, detail, cornsweet, late, 1960s, kenneth, craik, vivian, brien, made, earlier, observations, similar, vein, example, whole, left, half, this, rectangle, seems, lighter, t. The Cornsweet illusion also known as the Craik O Brien Cornsweet illusion or the Craik Cornsweet illusion is an optical illusion that was described in detail by Tom Cornsweet in the late 1960s 1 Kenneth Craik and Vivian O Brien had made earlier observations in a similar vein 2 In an example of the Cornsweet illusion the whole left half of this rectangle seems to be lighter than the right In fact they have the same brightness apart from the gradients in the center The same image as above but the edge in the middle is hidden the left and right part of the image appear as the same color The original version of the illusion involved a rapidly spinning black and white disk painted in a way that would create the appearance of a gradient effect when in motion 3 An equivalent static version of illusion is composed of a gray rectangle where the left half fades to a lighter shade as it approaches a vertical center line and the right half fades to a darker gray approaching the same line As a result the whole left half of the rectangle appears lighter than the right half but in fact the brightness of both areas is exactly the same This can be seen by blacking out the region containing the edge This phenomenon is similar to the phenomenon of simultaneous contrast and Mach bands but differs from it in two important respects In Mach bands the effect is seen only on areas that are close to the intensity gradient In the Craik O Brien Cornsweet illusion a very small area the central edge affects the perception of entire large areas portions of which are distant from the edge In the Cornsweet illusion the region adjacent to the light part of the edge appears lighter and the region adjacent to the dark part of the edge appears darker just the opposite of the usual contrast effects The actual distribution of luminance in the picture and the typical perception of luminance A far more convincing and dramatic version of the effect can be seen in the article by Purves Lotto and Nundy 4 where it is presented within a quasi realistic image of solid illuminated objects 5 These writers give an explanation of this and other illusions in which the visual system and brain are posited to generate percepts on an empirical basis that is much like a reflex In their words perception accords not with the features of the retinal stimulus or the properties of the underlying objects but with what the same or similar stimuli have typically signified in the past citation needed References edit Cornsweet T 1970 Visual Perception New York Academic Press Colman Andrew M 2015 Craik O Brien effect A Dictionary of Psychology 4th ed Oxford University Press pp 175 176 ISBN 9780191057847 Lotto R Beau The Cornsweet Illusion Figure 2 researchgate net Retrieved 4 November 2021 Purves D Lotto R B Nundy S 2002 Why We See What We Do American Scientist 90 3 236 243 Archived copy https web archive org web 20150228222043 https www americanscientist org include popup fullImage aspx key a 2F9TzeCnMGhUDKw5aZ77Tg4fFGhe5fVLOriginal was at http www americanscientist org include popup fullImage aspx key a 9TzeCnMGhUDKw5aZ77Tg4fFGhe5fVL Quasi realistic image from Purves Lotto and Nundy 2002 showing a much more convincing presentation of the Cornsweet illusion Further reading editPurves D Shimpi A Lotto RB 1999 An empirical explanation of the Cornsweet effect J Neurosci 19 8542 8551 Purves D Lotto RB 2003 Why We See What We Do An Empirical Theory of Vision Sunderland MA Sinauer Associates Purves D Lotto RB 2004 The Cornsweet effect Encyclopedia of Neuroscience 3rd edition Elsevier Science Publishing Co External links editCraik O Brien Cornsweet Illusion by Michael Bach Retrieved from https en wikipedia org w index php title Cornsweet illusion amp oldid 1148594406, wikipedia, wiki, book, books, library,
