1. SENSATION
AND
PERCEPTION

5. Sensation and Perception
I. Detecting, Processing and
Interpreting Experiences
II. Sensory Receptors
III. Sensory Thresholds
IV. Habituation and Sensory Adaptation
V. The Sensory Organs
VI. Perceiving Sensory Stimuli

6.  SENSATION
the process of receiving stimulus
energies from the external
environment
- sensory organs:
eyes (visual system)
ears (auditory)
nose (olfactory)
tongue (gustatory)
skin (tactile)

7.  PERCEPTION
the process of
organizing and Prior experiences
interpreting Expectations
sensory Memory
information to Biases
give it meaning.

8. Why is it important to study
sensation and perception?
 The purpose of perception is:
1) to represent information from the
outside world internally;
2) adaptation that improves a species’
chances for survival; and
3) to help in designing devices to restore
perception to those who have lost some
(or all) and also to devise treatments for
other perceptual problems.

9. Have you ever experienced
(or seen someone) bumping into a
clear window glass because you
did not know that it was there?

10.  BOTTOM-UP PROCESSING
- Sensory receptors register information
about the external environment and send it
up to the brain for analysis and
interpretation.
 TOP-DOWN PROCESSING
- Starts out with cognitive processing at the
higher levels of the brain.
- Cognitive processes include knowledge,
beliefs and expectations.

11. JIGSAW PUZZLE

12. SENSORY RECEPTORS
 All sensation begins with sensory receptors.
 Sensory receptors are specialized cells
that detect and transmit stimulus
information to sensory nerves and the
brain.

13. SENSORY THRESHOLDS
 Buzzing mosquito?
 Difference between regular Coke and Coke
Zero?

14. SENSORY THRESHOLDS
 Absolute threshold
- Minimum amount of energy that a person
can detect
 Difference threshold
- just noticeable difference (jnd)
- the degree of difference that must exist
between two stimuli before the difference is
detected.

15. SENSORY THRESHOLDS
 Absolute Threshold
- Orange juice
- One tablespoon?
- Two tablespoon?
- Three tablespoon!
- Watching TV while your roommate is
sleeping.
- Volume?

16. 
2 4 6 9 1213

17. Approximate Absolute Thresholds
 Vision
- A candle flame at 30 miles on a dark, clear night.
 Hearing
- A ticking watch at 20 feet under quiet conditions.
 Smell
- One drop of perfume diffused throughout 3 rooms
 Taste
- A teaspoon of sugar in 2 gallons of water
 Touch
- The wing of a fly falling on your cheek from a distance
of one centimeter.

18.  Difference Threshold
- Watching TV while your roommate is
sleeping.
- Your roommate, suddenly wakes-up.
- Also wants to watch the TV!
- Volume?

19. JND!
No JND!

2 4 6 9 1213

20.  A student late for his class.
10: 03 – late?
10:05 – late?
10: 10 – late?
10:15 – late!!!
It takes 15 minutes for a student to be
detected as late.
Absolute or difference threshold?
*Depends on the individual who perceives and
the condition of the environment.

21.  Subliminal Perception
- the ability to detect information below the
level of conscious awareness.
- JAMES VICARY (1957)
- “Eat Popcorn”; “Drink Coke”
- .003 second once every 5 secs.
- The sales of popcorn and coke increased!
- HOAX!
- Subliminal perception does not work in
advertising.

22. HABITUATION AND SENSORY
ADAPTATION
 The lower centers of the brain sort through
sensory stimulation and “ignore” or prevent
conscious attention to stimuli that do not
change.
 Sound of aircon
 Smell of garbage
 Reading your readings?

23.  Sensory adaptation
- The sensory receptor cells become less
responsive to an unchanging stimulus.
- The receptors are no longer sending signals
to the brain.
 Habituation
- The sensory receptor cells are still
responding to the stimulus, but the lower
centers of the brain are not sending
the signals from those receptors in the
cortex.

24. QUESTIONS?