Chapter 3
SENSATION AND PERCEPTION
WHAT IS SENSATION?

Sensation is the process in which we receive,
transform, and process stimuli from the outside
world to create sensory experiences of vision,
touch, hearing, taste, smell and so on.

There are actually 7 body senses, not just the 5
we normally think of.
SENSATION

Sensory receptors- Specialized cells that detect
sensory stimuli and convert them into neural
impulses, which the brain uses to create the
sensations of our senses.

Absolute Threshold- The smallest amount of a
given stimulus a person can sense.
ABSOLUTE THRESHOLDS
Sense
Stimulus
Receptors
Threshold
Vision
Light energy
Rods and cones in
the eye
Flame from a single
candle 30 miles
away
Hearing
Sound waves
Hair cells in the
inner ear
Ticking of a watch
about 20 ft. away
Taste
Chemical
substances that
contact the tongue
Taste buds on the
tongue
One teaspoon of
sugar dissolved in 2
gallons of water
Smell
Chemical
substances that
enter the nose
Receptor cells in the One drop of
upper nostrils
perfume dispensed
in a small house
Touch
Movement of, or
pressure on, the
skin
Nerve endings in
the skin
The wing of a bee
falling on the cheek
from about 1 cm.
ERNST WEBER 1795-1878

Came up with the idea of difference threshold
or just-noticeable difference.

Difference Threshold- The minimal difference
between 2 stimuli that people can reliably
detect.
WEBER’S LAW

The amount you must change a stimulus to detect a
difference is given by a constant fraction or
proportion.
 Ex. Weber’s constant for noticing a difference in
weight is 1/50 or 2%
 If you were lifting a 50 lb. weight, you would
probably not notice a difference unless the weight
were increased or decreased by 2% (1 lb.).
WEBER’S LAW
If you were lifting a 50 lb. weight, you would
probably not notice a difference unless the
weight were increased or decreased by 2% (1
lb.).
 But, if you were lifting a 200 lb. weight, the
weight would have to be increased or reduced
by 4 lbs. (2%) to notice a difference.

SIGNAL DETECTION THEORY
 Detection
of a stimulus depends on
these factors
The intensity of the stimulus
The level of background stimulus
Biological and psychological
characteristics of the perceiver.
SIGNAL DETECTION THEORY

Physical condition can play a role in Signal
Detection
 Sense
of smell is more dull if your nose is stuffed or
if you have a cold.
 Alertness levels affect signal detection
 Motivation: Walking down a dark alley, staying
home alone (notice sounds).
 Hunger: Aromas or TV commercials when you
haven’t eaten in a while
SENSORY ADAPTATION

The process by which sensory receptors adapt
to constant stimuli by becoming less sensitive
to them.
 Cold swimming water
 Wristwatch, ring
 Music
 Odors ( i.e., men’s locker room)
PERCEPTION
 Perception-
The process by which the
brain interprets sensory information,
turning it into meaningful representations
of the external world.
 Through perception, our brain attempts to
make sense of the mass of sensory
stimuli that impinge on our sensory
organs.
ATTENTION: DID YOU NOTICE THAT?
 Attention
is the first step in perception.
 Through selective attention you limit your
attention to certain stimuli while filtering
out other stimuli.
 Selective attention prevents you from
being flooded with extraneous
information.
ATTENTION: DID YOU NOTICE THAT?
 We
pay more attention to stimuli that are
meaningful or emotionally significant.
 Motivational states, such as hunger or
thirst, play important roles in attention.
 When we are hungry, we are more likely
than when we’ve just eaten to pay
attention to odors wafting out of a
restaurant.
ATTENTION: DID YOU NOTICE THAT?
 Repeated
exposure may increase
attention to particular stimuli.
 On the other hand, exposure to a constant
stimulus can lead us to become
habituated, or accustomed, to a stimulus.
 Ex. The humming sound of an air
conditioner
MODES OF VISUAL PROCESSING: BOTTOM-UP
VS. TOP-DOWN
 Bottom-up
Processing- The brain
assembles specific features of shapes,
such as angles and lines, to form patterns
that we can compare with stored images
we have seen before.
 Bottom-up processing may also be used to
combine the individual elements of letters
and words into recognizable patterns.
MODES OF VISUAL PROCESSING: BOTTOM-UP
VS. TOP-DOWN
 Top-Down
Processing- perceiving patterns
as meaningful wholes- such as
recognizing faces of people we knowwithout needing to piece together their
components.
 Top-down is based on acquired experience
and knowledge with patterns, but it is not
perfect.
GESTALT LAWS OF GROUPING
 People
tend to group bits and pieces of
sensory information into unitary forms or
wholes.
 Gestalt psychologists described several
principles of grouping, including proximity,
similarity, continuity, closure, and
connectedness.
GESTALT LAWS OF GROUPING

Proximity- the principle that objects that are
near each other will be perceived as belonging
to a common set.
GESTALT LAWS OF GROUPING

Similarity- The principle that objects that are
similar will be perceived as belonging to the
same group.
GESTALT LAWS OF GROUPING

Continuity- The principle that a series of stimuli
will be perceived as representing a unified
form.
GESTALT LAWS OF GROUPING

Closure- The perceptual principle that people
tend to piece together disconnected bits of
information to perceive whole forms.
GESTALT LAWS OF GROUPING

Connectedness- The principle that objects
positioned together or moving together will be
perceived as belonging to the same group.
GESTALT USE IN SPORTS LOGOS
GESTALT USE IN SPORTS LOGOS
GESTALT USE IN SPORTS LOGOS
GESTALT USE IN SPORTS LOGOS
GESTALT USE IN SPORTS LOGOS