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(1) an inadequate understanding of a perceived object that goes beyond the bounds of ordinary errors of perception; illusions represent a phenomenon that is largely unconscious and not subject to voluntary correction; (2) false, unrealizable hopes and dreams.

An examination of a few examples of illusory perception may be found in authors of antiquity (Aristotle, Lucretius, and Vi-truvius). During the Renaissance and in modern times, interest in illusion was cultivated by studies in optics and elaboration of the theory of perspective. However, it was only with the work of S. Oppel (1854, Germany) that the study of illusions acquired a systematic character. Illusion was first interpreted as an independent phenomenon by Gestalt psychology (M. Wertheimer, 1912, Germany). The most significant investigations of illusion in contemporary psychology have been conducted by the schools of the Soviet psychologist D. N. Uznadze and the Swiss psychologist J. Piaget.

So-called opticogeometric illusions (optical illusions)—that is, illusions in perceiving weight, time, various types of seeming and induced movement, and effects of a succession of fixed arrangements—are generally known; illusions that arise under complex special conditions have also been studied. Each illusion produces in experiments its own curve of errors of perception, which are determined by quantitative indexes.

The majority of illusions are either weakened (primary illusions) or strengthened (secondary illusions) with age, thus revealing a close connection with the total course of perceptual development, specifically with the formation of its constancy. Illusions have long been used in art, making possible special effects of expressiveness. It is necessary to take account of the laws of illusory perception in any type of direct observation and evaluation and also in architecture and the design of manufactured articles.


Illusions in medicine. Illusory deceptions of the senses can occur in healthy persons, but are characteristic mainly of persons with acute or chronic mental disturbances. They often arise as a result of fatigue, exhaustion, fear, or an anxious-depressed state. A suspicious attitude toward the environment can cause illusions—for example, a fearful traveler in the forest is capable of mistaking a bush for a hidden malefactor; to a delirious patient, spots on the wall may appear to be trees or animals; an intoxicated alcoholic may hear reproaches and abuse addressed to himself in the speech of the street crowd.

Illusions may be visual, auditory, tactile, gustatory, or olfactory. They differ from hallucinations by the presence of a real object of perception. Besides illusions as psychopathological phenomena, there are “physical illusions”—phenomena that are observed by everyone, regardless of mental peculiarities.



Gregori, R. L. Glaz i mozg. Moscow, 1970.
Piaget, J. Les Mecanismes perceptifs. Paris, 1961.
Carraher, R.G., and J. B. Thurston. Optical Illusions and the Visual Arts. New York, 1966.
References in periodicals archive ?
The Museum of Illusions, which was formally inaugurated at the Muscat Grand Mall on Monday, will give you a first-hand experience of these things.
The Museum of Illusions, which is managed by a young Omani entrepreneur, is located in the newly launched expanded section of the mall.
I'm privileged to share with you some of my favorite illusions that I have created over the years.
Dr Mike Pickard's clever transformation of LS Lowry's 'Returning from Work' has earned him a shortlisting in the international visual science competition, Best Illusion of the Year.
Created with high-quality fragrance oils, Lasting Illusions launched last fall with nine SKUs.
Visual illusions demonstrate the ways in which the brain creates a mental representation that differs from the physical world," said Martinez-Conde.
Knowing the details of the airport where you plan to land can help a pilot mitigate the risks of these illusions.
In each of the illusions, the authors demonstrate their pervasiveness and the effect they have on behavior.
The Illusions of Entrepreneurship: The Costly Myths That Entrepreneurs, Investors, and Policy Makers Live By" is an examination of modern entrepreneurship and what makes it all tick.
The Foundation of the American Academy of Ophthalmology and its Museum of Vision have created and made available two free downloadable teacher workbooks, Eye Openers: Exploring Optical Illusions and Art and Vision: Seeing in 3-D[R].
Joseph Haj, DIRECTOR: In this adaptation by Tony Kushner of Corneille's play--it's more Kushner than Corneille--a sorcerer conjures up three illusions for a father who's searching for his son, whom he hasn't seen in 15 years.
His goal is to help mental health professionals create effective treatment strategies for patients whose problems are fueled by and organized around powerful illusions about themselves and their world.