An illusion is a distortion of the senses,
revealing how the brain normally organizes
and interprets sensory stimulation
Sensations can be defined as the passive process of
bringing information from the outside world into the body
and to the brain. The process is passive in the sense that
we do not have to be consciously engaging in a "sensing"
What your mind feels or registers.
Perception can be defined as the active process
of selecting, organizing, and interpreting the
information brought to the brain by the senses.
What your mind fells or registers and also
Optical illusions are
intriguing example of
how easily the mind
can get confused.
recognize the face in
this painting but if you
look at his hair, you'll
see that he is fighting a
Are the squares above marked A & B
the same color or different?
Proof: They are the same. The
shadow causes an illusion of white.
Adelson`s „Checker-shadow illusion“
Adelson EH (1993)
Perceptual organization and
the judgment of brightness.Science 262:2042-2044
Luminance & Contrast
Which line is longer?
They are actually the same size.
Eye-movement theory: Arrowheads influence
extent of eye movements
Pictures converted in our brain from 2-
dimensional drawings to represent 3-
Different level of explanation – does not
propose a mechanism for perception
Well established, although some ‘loopholes’
have been found
Cochran’s photo of his ‘freemish’ crate (1966).
Adelbert Ames, Jr. (1946) – concept by
Special viewpoint – monocular
Floor, ceiling, some walls, & windows are
Appears as a normal
A split between perception & expectation
Apparent cubic perspective overrides sense of
Robert Shepherd – use
relationship to the horizon
to judge size