What is an optical illusion?
Q: What is an optical illusion?
A: An optical illusion is a visual image that differs from reality. It occurs when the information gathered by the eye is processed in the brain to give a perception that does not match with a physical measurement of the stimulus source.
Q: What are the three main types of visual illusions?
A: The three main types of visual illusions are literal optical illusions, physiological illusions, and cognitive illusions. Literal optical illusions create images which are different from the objects that make them, physiological illusions are caused by over-stimulation of brightness, colour, size, position, tilt or movement; and cognitive illusions occur as a result of unconscious inferences made by the brain.
Q: How do we perceive things according to Hermann von Helmholtz?
A: According to Hermann von Helmholtz's model of perception, we use our brains to work out what it is we are looking at based on sense data and past experience. This involves using memory and logic at a fast rate but can sometimes fail resulting in an illusion.
Q: What does Richard Gregory think about how our brains perceive things?
A: Richard Gregory believes that our brain makes an hypothesis about what's out there based on sense data and previous knowledge and experience which can sometimes lead to wrong decisions resulting in an illusion.
Q: What does Mark Changizi think causes optical illusions?
A: Mark Changizi believes that optical illusions occur due to a 'neural lag' where light hits the retina but takes one-tenth of a second for the brain to translate it into a visual perception. He suggests that humans have evolved to compensate for this neural delay by generating images of what will occur one-tenth of a second into the future which can sometimes lead to wrong perceptions resulting in an illusion.
Q: How do scientists explain most cases of illusory phenomena?
A: Scientists generally explain most cases of illusory phenomena as being caused by how our brains work on sense data to produce meaningful perceptions which can sometimes be incorrect leading us to see something differently than reality creating an illusion.
