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1. Introduction to Psychology
Sensation and Perception

2. Sensation
• Sensory information
• Includes vision, hearing, smell,
taste, touch balance, body
position, movement, pain, and
temperature
• Absolute threshold
• Messages that are presented
below the threshold for conscious
awareness are called subliminal
messages.
• Difference threshold

3. Perception
• How sensory information is interpreted and consciously
experienced
• Sensation is a physical process, whereas perception is
psychological
• Attention and motivation determine what is sensed
versus what is perceived
• Sensory adaptation

4. Anatomy of Vision

5. Photoreceptors in the Fovia Detect Light

6. From Eye to Brain
Note the optic nerve, optic chiasm and the pathways to the occipital lobe,
where visual sensations are processed into perceptions

7. Visual Information in the Brain
Visual information is processed in parallel pathways which can
generally be described as the “what pathway” (the ventral pathway)
and the “where/how” pathway (the dorsal pathway)

8. Light Waves and the Electromagnetic Spectrum
Light enters the eye as a wave

9. The Visible Spectrum
Different wavelengths of light are associated with our perception of
different colors

10. Two Theories of How We See
Color
Trichromatic
• The cones respond to three
wavelengths that represent
red, blue, and green.
• All colors can be produced by
combining red, blue, and
green.
• Applies to visual processing
on the retina
Opponent Process
• Color is coded in opponent
pairs: black-white, yellow-
blue, and green-red.
• Cells of the visual system are
excited by one of the
opponent colors and inhibited
by the other.
• Explains why we can’t see
greenish-red and why there
are afterimages.
• Applies once the signal
moves past the retina on its
way to the brain

11. Depth Perception
• Depth perception: ability to perceive spatial
relationships in (3-D) space
• Binocular cues
• Monocular cues

12. Anatomy of the Auditory System

13. Sound Waves
• Sound waves travel
into our ears at
various speeds and
amplitudes
• Higher amplitudes
are associated with
louder sounds
• High-frequency
sound waves are
perceived as high-
pitched sounds

14. Two Theories of Pitch
Perception
Temporal
• Frequency is coded by
the activity level of a
sensory neuron.
• Applies to frequencies
of up to 4000 Hz
Place
• Different portions of the
basilar membrane are
sensitive to sounds of
different frequencies
• Place contributes to pitch
perception for frequencies
under 4000 Hz.
• Much higher frequency
sounds can only be encoded
using place cues.

15. Sound Localization
Monaural (one-eared) Each
pinna interacts with incoming
sound waves differently,
depending on the sound’s
source relative to our bodies.
Binaural (two-eared) cues:
1. Interaural level difference
2. Interaural timing difference

16. Types of Hearing Loss
• Deafness
• Congenital deafness
• Conductive hearing loss
• Sensorineural hearing loss

17. Taste
Molecules from the food and beverages we consume dissolve in our
saliva and interact with taste receptors on our tongue (below) and in
our mouth and throat

18. Smell
Olfactory receptors are proteins with pockets that identify molecules
of chemicals in the air. This information is transmitted from the
olfactory bulb to the brain

19. Touch
Specific receptors in the skin convert stimulation to electrical nerve impulses,
a process called transduction
• Mechanoreceptors (below) respond to mechanical stimuli, such as
stroking, stretching, or vibration of the skin
• Thermoreceptors respond to cold or hot temperatures
• Chemoreceptors respond to certain types of chemicals either applied
externally or released within the skin

20. Pain
Pain is adaptive because it makes us aware of an injury, and it
motivates us to remove ourselves from the cause of that injury
• Neuropathic pain
• Inflammatory pain
• Nociceptors are subtypes of chemoreceptors or
mechanoreceptors that fire specifically to potentially tissue-
damaging stimuli
Expectations and context shape how we experience pain

21. Pain and the Somatosensory Cortex
Pain is signaled via fast-
conducting A-fibers,
which project to the
somatosensory cortex
This part of the cortex is
somatotopically
organized—that is, the
sensory signals are
represented according to
where in the body they
stem from

22. Pain Processing Pathways

23. The Vestibular System
The major sensory
organs of the vestibular
system are located next
to the cochlea in the
inner ear

24. Proprioception and Kinesthesia
Definition Example
Vestibular Sense
Sensory system that contributes to
balance and the sense of spatial
orientation.
You have an ear infection
and feel dizzy.
Propioception Perception of body position.
You step off a curb and
know where to put your
foot. You push an elevator
button and control how
hard you have to press
down with your fingers.
Kinesthesia
Perception of the body’s movement
Key component in muscle m emory and
hand-eye coordination.
You are aware of your arm
movement while swinging
a golf club.

25. Gestalt Principles of Perception
The brain creates a perception that is more than simply
the sum of available sensory inputs

26. Figure-Ground Relationship
The concept of figure-
ground relationship
explains why this image
can be perceived either as
a vase or as a pair of
faces

27. Proximity
The Gestalt principle of proximity suggests that you see
(a) one block of dots on the left side and (b) three
columns on the right side

28. Similarity
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

29. Continuation
Continuation would suggest that
we are more likely to perceive this
as two overlapping lines, rather
than four lines meeting in the
center

30. Closure
Closure suggests that we will perceive a complete circle
and rectangle rather than a series of segments

31. Multimodal Perception
Multimodal perception is the effect stimulation of multiple
senses has on perception.
• Multimodal phenomena
• McGurk Effect
• Rubber Hand Illusion
• Crossmodal phenomena
• Double flash illusion
• Ventriloquism effect

32. Why Do Psychologists Use Illusions?
Perception scientists create illusions to explore perception, what parts of the
brain are involved in interpretation of the illusion, and what variables
increase or diminish the strength of the illusion.

33. Practice Question
Based on what you have learned about pain, how might
we treat pain other than pharmaceuticals?

34. Quick Review
• What is the difference between sensation and
perception?
• How does vision work?
• How do people see color and depth?
• How does hearing work?
• What are the basic anatomy and functions of taste,
smell, touch, pain, and the vestibular sense?
• What is perception?
• What are some examples of gestalt principles and
multimodal perception?