Sensation and Perception
By
Course Instructor: Samreen Umar
Lecturer at Department of Psychology, UOS
Defining Sensation and Perception
Sensation
Input of sensory information
Process of receiving, converting, and
transmitting information from the outside
world
It occurs when energy in the external
environment or the body stimulates receptors
in the sense organs.
Perception
The process by which the brain organizes
and interprets sensory information.
It refers to interpretation of what we take in
through our senses. The way we perceive
o u r e n v i r o n m e n t i s w h a t m a ke s u s
different from other animals and different
from each other
Perception is inf lu enced by a person's
experiences, motives, expectations, and
Sensation & Perception
Processes
Absolute Threshold
The smallest quantity of physical energy that
can be reliably detected by an observer.
Difference Threshold
The smallest difference in stimulation that
can be reliably detected by an observer when
two stimuli are compared.
Absolute Sensory Thresholds
Vision:
A single candle flame from 30 miles on a dark,
clear night
Hearing:
The tick of a watch from 20 feet in total quiet
Smell:
1 drop of perfume in a 6-room apartment
Touch:
The wing of a bee on your cheek, dropped from
1 cm
Taste:
1 tsp. Sugar in 2 gal. water
Vision
The eye captures light and focuses it on the
visual receptors, which convert light energy
to neural impulses sent to the brain
Hearing
Audition (hearing) occurs via sound
waves, which result from rapid
changes in air pressure caused by
vibrating objects
Receptors located in the inner ear
(cochlea) tiny hair cells that convert
sound energy to neural impulses sent
along to brain
An Ear on the World
Taste: Savoury Sensations
Gustation - (taste) receptors are taste buds on tongue.
Four basic tastes: sweet, salty, sour and bitter
Smell: The Sense of Scents
Airborne chemical molecules enter the nose and
circulate through the nasal cavity.
Receptors at the top of the nasal cavity detect
these molecules.
Sensitivity to Touch
Vestibular sense (sense of balance)
results from receptors in inner ear
Kinesthesis - (body posture, orientation
, and body movement) results from
receptors in muscles, joint and tendons
Skin senses detect touch (pressure,
temperature and pain)
Principles of perception
Gestalt Psychologist believed that the whole is different from the
sum of its parts. In other words, the brain creates a perception that
is more than simply the sum of available sensory inputs, and it does
so in predictable ways. Gestalt psychologists translated these
predictable ways into principles by which we organize sensory
information. As a result, Gestalt psychology has been extremely
influential in the area of sensation and perception.
Gestalt principles such as figure-ground relationship, grouping by
proximity or similarity, the law of good continuation, and closure are
all used to help explain how we organize sensory information. Our
perceptions are not infallible, and they can be influenced by bias,
prejudice, and other factors
Figure-ground relationship.
According to this principle, we tend to segment our
visual world into figure and ground. Figure is the object
or person that is the focus of the visual field, while the
ground is the background
Proximity
Another Gestalt principle for organizing sensory stimuli
into meaningful perception is proximity. This principle
asserts that things that are close to one another tend to
be grouped together
Similarity
According to this principle, things that are alike tend to be
grouped together is Similarity. For example, When looking at
this array of dots, we likely perceive alternating rows of colors.
We are grouping these dots according to the principle of
similarity.
Law of continuity
The law of continuity suggests that we are more
likely to perceive continuous, smooth flowing lines
rather than jagged, broken lines
Principle of closure
The principle of closure states that we
organize our perceptions into
complete objects rather than as a
series of parts
According to Gestalt theorists, pattern
perception, or our ability to discriminate
among different figures and shapes, occurs by
following the principles described above. You
probably feel fairly certain that your perception
accurately matches the real world,
Perception is a complex process. Built from
sensations, but influenced by our own
experiences, biases, prejudices, and cultures,
perceptions can be very different from person
to person
Role of perception in human
cognition
Perception refers to the ability of the mind to
ap p re he nd o b j e c t s t hro ug h t he se nso ry
modalities of sight, hearing, smell touch and
taste while cognition is the thinking about the
perceptions in terms of individual previous
experience. Hence cognitive process may entail
the re c al l o f p re v i o us e x p e ri e nc e o r the
evaluation of the objects perceived
