SENSATION AND
PERCEPTION
Alazar Tesfaye (MA)
April, 2023
Presentation outline
Presentation objectives Perception
Meaning of sensation and perception Visual perception
The differences and similarities of sensation and perception
Selection
The factors affecting sensation and perception Environmental/stimulus factors
Th principles of sensation and perception Psychological factors
Physiological factors
Organization
Sensation
Gestalt principles of grouping
Sensory thresholds Form perception
Movement perception
Absolute Threshold
perceiving distance / depth perception
Difference threshold Maintaining perceptual constancy
Just noticeable difference (JND) Perceptual illusion (visual illusion)
Weber’s law Interpretation
Signal detection theory Beliefs
Sensory Adaptation Emotions
Expectations
Sensory Deprivation
Extrasensory perception (ESP)
Sensory Overload
Telepathy
Clairvoyance
Precognition
Psycho kinesis
Sensation
Sensation refers to the process of sensing our
environment through our sense organs and send it
to the brain.
TOUCH TASTE SMELL SIGHT SOUND
Sensation
SENSORY SENSORY
THRESHOLDS
The point at which a stimulus causes a sensation within A reduction in ADAPTATION
sensitivity to a stimulus after
an individual. constant exposure to it.
Sensory Thresholds
Absolute Thresholds Difference Thresholds
Absolute Thresholds
◦ It is the point where something becomes noticeable to our senses.
◦ It’s the softest sound we can hear or the slightest touch we can feel.
◦ It is the point at which a stimuli goes from undetectable to detectable sates to
our senses
Difference Thresholds
◦ It is the difference in the level of the stimulus needed for a person to recognize that a change has
occurred.
◦ It’s the just noticeable difference of the stimuli (JND).
◦ Weber’s law: the amount of change that is necessary to be noticed is systematically related to
the intensity of the original stimulus.
◦ (E.g. Imagine holding a five pound weight and one pound was added. Most of us would notice this difference. But what if we holding fifty
pound weight and one pound was added? Would we notice?)
◦ Signal detection theory: the ability to detect what we want to focus on and ignore or minimize
everything else.
Sensory Adaptation
Sensory Deprivation Sensory Overload
N.B. Too much or too little sensory experience is harmful to the body.
Perception
Perception refers to the process by which the brain
selects, organizes, and interprets these sensations.
TOUCH TASTE SMELL SIGHT SOUND
Perception
SELECTION ORGANIZATION INTERPRETATIO
Focusing attention on certain
stimuli in our environment.
Arranging information into
meaningful and digestible patterns. selected.
N
Assigning meaning to the information
Visual Perception
SELECTION
There are factors that influence the process of selective attention
ENVIRONMENTAL PSYCHOLOGICAL PHYSIOLOGICAL
FACTORS FACTORS FACTORS
Environmental/stimulus Factors: when the focus of attention is attracted to
objects or events that possess unusual characteristics or that provide strong
stimulation to the sense organs.
INTENSITY SIZE CONTRAST
REPETITIO MOVEMEN NOVELTY
N T
Intensity
The more intense the stimulus
the more it will be attended.
E.g. A bright color will attract us
more than the dull one.
Size
we tend to notice larger
compered to smaller one.
Contrast
what contrasts with the
surrounding environment
attracts attention easily.
Repetition
A fleeting stimulus will not
catch our attention as easily
as one which is repeated.
Movement
Something which moves is
more likely to attract attention
than something stationary.
Novelty
A sudden or unexpected stimulus
is likely to catch our attention
more easily than the one we have
been expecting or that we have
encountered
Psychological Factors: the focus of attention is also affected by certain
characteristics of individuals.
MOTIVATION PERSONALITY AND
INTEREST
MOTIVATION Personality and Interest
what we choose to hear or perceive is For example, in a football game, an ex-player
determined largely by your current level of may give attention to the football game, his wife,
satisfaction or deprivation. a singer, may give attention to the music in the
stadium, and a friend, a commentator, may give
E.g. when you are hungry. You are much more
attention to the way the referee is handling crisis
likely to notice TV commercials for doughnuts,
situations in the play.
hamburger, pizza than those for cars or
detergent.
Physiological
Factors
One of the major physiological
factors in selection is the presence of
specialized cells in the brain called
Feature detectors (feature analyzers)
that respond only to certain sensory
information.
Visual Perception
ORGANIZATION
There are factors that influence the process of organization
GESTALT LAW FORM MOVEMENT
OF GROUPING PERCEPTION PERCEPTION DEPTH PERCEPTUAL PERCEPTION
PERCEPTION CONSTANCY ILLUSION
Gestalt law of grouping
Gestalt principles of grouping, it describe how humans group similar
elements, recognize patterns and simplify complex images when we perceive
objects. Humans naturally perceive objects as organized patterns.
Form perception
SIMILARIT PROXIMITY CONTINUIT CLOSURE FIGURE
Y Y AND
GROUND
FIGURE AND
GROUND
The tendency of the visual system to
simplify a scene into the main object
that we are looking at (the figure)
and everything else that forms the
background (or ground).
The concept of figure-ground perception is
often illustrated with the classic "faces or
vases" illusion, also known as the Rubin
vase.
Depending on whether you see the black or
the white as the figure, you may see either
two faces in profile (meaning you perceive
the white color as the figure) or a vase in
the center (meaning you see the dark color
as the figure).
Similarity
When things appear to be
similar to each other, we group
them together. And we also tend
to think they have the same
function.
Proximity
The principle of proximity tells we
perceive elements that are close to
each other appear to be related.
Even if there are more objects, the
ones that are closer seems to be
more correlative than elements that
are placed farther.
Continuity
Elements that are arranged on a
line or curve are perceived to be
more related than elements not
on the line or curve.
Closure
We look at a complex arrangement
of visual elements, we tend to look
for a single, recognizable pattern.
In other words, when you see an
image that has missing parts, your
brain will fill in the blanks and make
a complete image so you can still
recognize the pattern.
Movement perception
REAL MOVEMENT APPARENT
MOVEMENT
Real movement Apparent movement
1. An image moves across the retina. 1. Phi-phenomena /stroboscopic
A succession of still pictures projected fast on a
2. The eyes move in the head to follow the path
screen gives a false impression of movement
of the moving object
2. Auto-kinetic
It is caused by the slight movement of the eye’s
focal point
3. Induced
occurs when a moving object creates apparent
movement on a relatively static object
Depth Perception: helps us estimate an object’s
distance and full shape.
MONOCULAR CUES BINOCULAR CUES
Perceptual constancy
SIZE CONSTANCY SHAPE CONSTANCY BRIGHTNESS
CONSTANCY
Size constancy
The ability to perceive an object
as being the same size despite
the fact that the size of its retinal
image changes depending on its
distance from the observer.
Shape constancy
It refers to the phenomenon in
which the percept of the shape of
a given object remains constant
despite changes in the shape of
the object's retinal image.
Brightness
constancy
The tendency to perceive a
familiar object as having the
same brightness under different
conditions of illumination.
Perceptual illusion
PONZO ILLUSION HORIZONTAL MULLER LAYER MOON ILLUSION
VERTICAL ILLUSION
ILLUSION
Ponzo illusion
It tricks our brain into presuming
that the upper of the two lines
must be longer, because it
appears due solely to its
background to somehow be “in
the distance”.
Horizontal
vertical illusion
It refers to the human tendency
to overestimate or underestimate
the length of a vertical line
as opposed to a horizontal line
when these lines bisect (cross)
one another.
Muller layer
illusion
Illusion in which two lines of
the same length appear to be
of different lengths.
Moon illusion
An optical illusion in which the
moon appears larger when it is
closer to the horizon than when
it is higher in the sky.
Visual Perception
INTERPRETATIO
N
There are factors that influence the process of interpretation
BELIEFS EMOTIONS EXPECTATION
S
Extrasensory Perception, also called the sixth sense, includes claimed
reception of information not gained through the recognized physical senses, but
sensed with the mind.
TELEPATHY CLAIRVOYANC PRECOGNITIO PSYCHO
E N KINESIS
Telepathy: direct transference of thought Clairvoyance: the claimed ability to gain
from one person (sender or agent) to information about an object, person,
another (receiver or percipient) without location, or physical event through
using the usual sensory channels of extrasensory perception.
communication.
Precognition: knowledge of future events, Psycho kinesis: also called telekinesis,
with emphasis not upon mentally causing it’s the action of mind on matter, in which
events to occur but upon predicting those objects are supposedly caused to move or
the occurrence of which the subject claims change as a result of mental concentration
has already been determined. upon them.
Thank you for your attention!
I hope you enjoyed the presentation! 😉😊
