TYPES OF OPTICAL ILLUSIONS
PERCIEVING OPTICAL ILLUSIONS-
1. Role of eye
2. Role of Brain
• FACTORS CAUSING OPTICAL
• NATURAL OPTICAL ILLUSIONS
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 percept that does not tally with a physical
measurement of the stimulus source.
When we experience a visual illusion we may see
something that is not there or fail to see something
that is there or even see something that different
from what is there!
Because of this dissociation between perception and
reality, visual illusions demonstrate the ways in
which the brain can fail to recreate the physical
world. By studying these failings, we can learn
about the computational methods that the brain
uses to construct visual experience.
TYPES OF OPTICALTYPES OF OPTICAL
There are 3 main types of optical
LITERAL OPTICAL ILLUSIONS
COGNITIVE OPTICAL ILLUSIONS
I. LITERAL OPTICAL ILLUSIONS
Literal optical illusions are those illusions that create images
that are different from the objects that make them.
Physiological illusions are
presumed to be the effects
on the eyes or brain of
excessive stimulation of a
specific type - brightness,
tilt, color, movement, etc.
The theory is that stimuli
have individual dedicated
neural paths in the early
stages of visual processing,
and that repetitive
stimulation of only one or a
few channels causes a
that alters perception
III.III. COGNITIVE ILLUSIONSCOGNITIVE ILLUSIONS
Cognitive illusions are assumed to arise by interaction with in-built
assumptions or 'knowledge' of the world, leading to "unconscious
inferences", an idea first suggested in the 19th century. Cognitive
illusions are commonly divided into:
PARADOX ILLUSIONS OR FICTION ILLUSIONS
Ambiguous illusions are pictures or objects that elicit significant
changes in appearance. Perception will 'switch' between the alternates
as they are considered in turn as available data does not confirm a
single view. The Necker cube is a well known example. Another instance
is the Rubin vase.
1. AMBIGUOUS ILLUSIONS
Distorting illusions offer distortions of size, length, or
curvature.Example:cafe wall illusion
2. DISTORTING ILLUSIONS
Paradox illusions offer objects
that are paradoxical or
Penrose triangle is an illusion
dependent on a cognitive
adjacent edges must join.
3. PARADOX ILLUSIONS OR FICTION ILLUSIONS
ROLE OF BRAINROLE OF BRAIN
Retina isresponsible for converting light signals to neural signals.
Optic nerve starts at a point in retina called the blind spot
Optic chiasm:-the optic nerve meets here in the first part of the brain
The OCCIPITAL LOBE located posterior in the brain deals with vision
FACTORS CAUSING OPTICALFACTORS CAUSING OPTICAL
Following are the factors causing optical
3.Depth and distance
5.Lines and curves
Auroras are natural light displays in the sky, usually
observed at night, particularly in the polar zone. They
typically occur in the ionosphere
A mirage is a refraction phenomena in which the image of some object
appears displaced from its true position. A common example of a mirage
is the appearance of water some distance down the highway on a hot
BY THE WAY, HOW MANY LEGSBY THE WAY, HOW MANY LEGS
DOES THIS ELEPHANT HAS?DOES THIS ELEPHANT HAS?
Textbook of Medical Physiology by Arthur .C.
Elements of chordate anatomy By Charles K.
Biology textbook for class XII-NCERT