Author Topic: Optical illusion  (Read 298 times)

Offline Esrat

  • Jr. Member
  • **
  • Posts: 92
  • Test
    • View Profile
Optical illusion
« on: January 15, 2015, 02:46:05 PM »
An optical illusion (also called a visual illusion) is characterized by visually perceived images that differ from objective reality. The information gathered by the eye is processed in the brain to give a perception that does not tally with a physical measurement of the stimulus source. There are three main types: literal optical illusions that create images that are different from the objects that make them, physiological illusions that are the effects of excessive stimulation of a specific type (brightness, colour, size, position, tilt, movement), and cognitive illusions, the result of unconscious inferences. Pathological visual illusions arise from a pathological exaggeration in physiological visual perception mechanisms causing the aforementioned types of illusions.

Optical illusions are often classified into categories including the physical and the cognitive or perceptual, and contrasted with optical hallucinations.

Physiological illusions
Physiological illusions, such as the afterimages following bright lights, or adapting stimuli of excessively longer alternating patterns (contingent perceptual aftereffect), are 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, colour, 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.

Pathological visual illusions

A pathological visual illusion is a distortion of a real external stimulus and are often diffuse and persistent. Pathological visual illusions usually occur throughout the visual field, suggesting global excitability or sensitivity alterations. Alternatively visual hallucination is the perception of an external visual stimulus where none exists. Visual hallucinations are often from focal dysfunction and are usually transient.

Cognitive illusions
Cognitive illusions are assumed to arise by interaction with assumptions about the world, leading to "unconscious inferences", an idea first suggested in the 19th century by the German physicist and physician Hermann Helmholtz.Cognitive illusions are commonly divided into ambiguous illusions, distorting illusions, paradox illusions, or fiction illusions.

Offline Afroza Akhter Tina

  • Hero Member
  • *****
  • Posts: 720
  • Test
    • View Profile
Re: Optical illusion
« Reply #1 on: February 02, 2015, 02:04:19 PM »
interesting thing to know about  :)

Offline Afroza Akhter Tina

  • Hero Member
  • *****
  • Posts: 720
  • Test
    • View Profile
Re: Optical illusion
« Reply #2 on: February 23, 2015, 03:32:34 PM »
A bit difficult for me but good to know the important aspects,nice sharing ma'am

Offline Mosammat Arifa Akter

  • Full Member
  • ***
  • Posts: 166
  • Test
    • View Profile
Re: Optical illusion
« Reply #3 on: February 25, 2015, 03:11:26 PM »
Thanks for sharing
Mosammat Arifa Akter
Senior Lecturer(Mathematics)
General Educational Department
Daffodil International University