12 Mind-Bending Perceptual Illusions

Examples of perceptual constancy include brightness constancy, color constancy, shape constancy, and size constancy.

A misperception of a stimulus object, event, or experience, or a stimulus that gives rise to such a misperception or misconception; more generally any misleading, deceptive, or puzzling stimulus or the perceptual experience that it generates.

• The Power of Top-Down Processing. To get the ball rolling, here’s a good example of how expectations guide perception.
• The Skye Blue Café Wall Illusion.
• Confetti.
• The Rice Wave Illusion.
• The Tilted Road Illusion.
• Lightness Illusion.
• The Dynamic Ebbinghaus.
• The Dynamic Müller-Lyer Illusion.

In other words, illusions are cognitive experiences, not purely perceptual ones: to appreciate an illusion we must have awareness of the discrepancy between our perceptual reality and the physical world; such awareness drives both on perceptual and cognitive material, but it is conflicting only at a cognitive level.

when the representation at the eye (retinal image) is variant with change in observer position, posture, and movement. These constancies are consequent on stimuli for object distance and observer posture and motion. When the retinal image is invariant and these stimuli are manipulated, perceptual illusions occur.

Visual illusions occur due to properties of the visual areas of the brain as they receive and process information. In other words, your perception of an illusion has more to do with how your brain works — and less to do with the optics of your eye.

Perceiver-distortion illusions Many common visual illusions are perceptual: they result from the brain’s processing of ambiguous or unusual visual information. Other illusions result from the aftereffects of sensory stimulation or from conflicting sensory information.

Some common synonyms of illusion are delusion, hallucination, and mirage. While all these words mean “something that is believed to be true or real but that is actually false or unreal,” illusion implies a false ascribing of reality based on what one sees or imagines.

Hallucinations vs Illusions The difference between hallucinations and illusions is that while hallucinations occur in the absence of any real external stimuli, illusions are episodes produced as a result of a mismatch between the external stimuli and its perception by the individual.

There are many causes of hallucinations, including:

• Being drunk or high, or coming down from such drugs like marijuana, LSD, cocaine (including crack), PCP, amphetamines, heroin, ketamine, and alcohol.
• Delirium or dementia (visual hallucinations are most common)

Treatment. To date, there is no successful method of treatment that “cures” musical hallucinations. There have been successful therapies in single cases that have ameliorated the hallucinations. Some of these successes include drugs such as neuroleptics, antidepressants, and certain anticonvulsive drugs.

Because we don’t know the exact mechanism of the auditory hallucinations, there is no single treatment for musical ear syndrome. Some people treat their hallucinations by changing their medications, or taking up meditation to manage stress levels.

If there is no underlying medical condition, changes to lifestyle may lessen the frequency of hallucinations. Getting enough sleep and avoiding drugs and alcohol can reduce their frequency. If hypnagogic hallucinations cause disrupted sleep or anxiety, a doctor might prescribe medication.

There is no definitive treatment for musical hallucinations. Treatment is aimed to treat the underlying cause if it is known. The majority of cases in which treatment has been effective depended on the resolution of the underlying cause (improving auditory deprivation, suspending the responsible pharmaceutical…).