OPTICAL ILLUSIONS• An experience of seeming to see something that does not exist or that is other than it appears.• Something that deceives ones eyes and causes such an experience.
OPTICAL ILLUSIONS• 1915, a cartoonist named W.E. Hill ﬁrst published this drawing• Is it a drawing of a pretty young girl looking away from us? Or is it an older woman looking down at the ﬂoor?• Titled, "Mother, Father, and daughter"
OPTICAL ILLUSIONS• They have been observed even in early history • ex. moon appearing larger on horizon• The architecture of ancient Greece reveals a knowledge of certain optical illusions in the efforts to over come them.• The study of optical illusions did not engage the attention of scientists until a comparatively recent period
OPTICAL ILLUSIONS• Result from information gathered by the eye being processed in the brain to give a perception that does not tally with a physical measurement of the stimulus source. • Literal optical illusions that create images that are different from the objects that make them • Physiological ones that are the effects on the eyes and brain of excessive stimulation of a speciﬁc type • Cognitive illusions, the result of unconscious inferences.
PHYSIOLOGICAL ILLUSIONS• Presumed to be the effects on the eyes or brain of excessive stimulation or interaction with contextual or competing stimuli of a speciﬁc type • Brightness, color, position, tile, size, movement, etc.• The theory is that a stimulus follows its individual dedicated neural path in the early stages of visual processing, and that intense or repetitive activity in that or interaction with active adjoining channels cause a physiological imbalance that alters perception.
COGNITIVE ILLUSIONS• Assumed to arise by interaction with assumptions about the world, leading to "unconscious inferences" • First suggested in the 19th century by Hermann Helmholtz.• Cognitive illusions are commonly divided into ambiguous illusions, distorting illusions, paradox illusions, or ﬁction illusions.
COGNITIVE ILLUSIONS• Object Consistencies • The brain has the ability to understand familiar objects as having a consistent shape or size • Unfamiliar objects, however, do not always follow the rules of shape constancy and may change when the perspective is changed.
COGNITIVE ILLUSIONS• Future Perception • Researcher Mark Changizi has a more imaginative take on optical illusions, saying that they are due to a neural lag which most humans experience while awake. • Changizi asserts that the human visual system has evolved to compensate for neural delays by generating images of what will occur one-tenth of a second into the future • This foresight enables humans to react to events in the present, enabling humans to perform reﬂexive acts like catching a ﬂy ball and to maneuver smoothly through a crowd. • Illusions occur when our brains attempt to perceive the future, and those perceptions dont match reality.
ILLUSIONS IN ART• Illusionscan be used to create space, motion, and perspective qualities in an art work.• Well known artists include: • M. C. Escher, Salvador Dali, Marcel Duchamp, etc.