cesia illusions

CESIA (illusions, graphic design…)

José Luis CAIVANO caivano@fadu.uba.ar

University of Buenos Aires and National Council for Research Argentine Color Group

What is an illusion

First group of definitions:

Because of a non-symmetrical relationship between physical stimuli and the impressions we have through our senses, every percept is an illusion. (This makes the concept of illusion itself meaningless).

Bela Julesz 1971: Every percept is an illusion. Light energy of a certain wavelength that impinges on our retinal receptors, does not inherently contain any indication that it will be perceived by some organisms in color of a given brightness, hue and saturation.

Edwin Boring 1942: The lack of correspondence between sensation and stimulus is obvious in many known phenomena. In the sense that perception is normally dependent upon subjective factors as well as upon the stimulus, all perception is “illusory� in so far as it does not precisely mirror the stimulus. Strictly speaking the concept of illusion has no place in psychology, because no experience actually copies reality.

What is an illusion

Second group of definitions:

There exists a true interpretation of physical phenomena, and because of a wrong perception we are lead to a false interpretation.

There are right percepts and illusory percepts.

Carraher and Thurston 1966: A visual illusion is a visual experience in which a discrepancy exists between our perceptual judgement and the actual physical character of the original stimulus.

Kaufman 1974: An illusion appears when observers are unable to discriminate the actual physical properties of objects and give a report that is not compatible with the physical arrangements of objects.

Tolanski 1964: Illusions are due to the imperfections of both our optical apparatus and of our intellectual appreciation for the situation presented to the brain.

These can lead to false interpretations.

What is an illusion

Third group of definitions:

An illusion is not a contradiction between perception and physical reality, it is a contradiction between two or more perceptions.

Graham 1965: Illusions are effects of contrasting experiences.

Da Pos 1995: An experience which is conflicting with other experiences, usually with remembered experiences. Only one experience is not enough to be considered an illusion because it does not produce a perceptive mismatch.

This mismatch, which is a consequence of two contrasting experiences, is according to me the main factor attracting our curiosity and exciting our aesthetic pleasure.

Colin y Blakemore 1973: A visual illusion is a discrepancy between two independent detector systems in the brain.

Paul Klee Polyphonic white 1930

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