This document provides an overview of Chapter 5 from a psychology textbook, which discusses sensation and perception. It begins with key questions about how sensation and perception affect individuals and the specific senses. It then outlines the 14 study units that will be covered, focusing on vision, hearing, taste, smell, and touch. These study units describe the physical stimuli detected by sensory receptors in each sensory system, and how the brain processes this sensory information into perceptions. Thresholds, adaptation, depth perception, motion perception, and object constancy are some of the topics addressed.

1. Chapter 5: Sensation and Perception

2. Chapter 5 Overview: Big Questions
• How Do Sensation and Perception Affect You?
• How Do You See?
• How Do You Hear?
• How Are You Able to Taste and Smell?
• How Do Your Feel Touch and Pain?

3. Chapter 5 Overview: Study Units
• 5.1 Your Senses Detect Physical Stimuli, and Your Brain Processes Perception
• 5.2 There Must Be a Certain Amount of a Stimulus for You to Detect It
• 5.3 Sensory Receptors in Your Eyes Detect Light
• 5.4 You Perceive Color Based on Physical Aspects of Light
• 5.5 You Perceive Objects by Organizing Visual Information
• 5.6 When You Perceive Depth, You Can Locate Objects in Space
• 5.7 Cues in Your Brain and in the World Let You Perceive Motion
• 5.8 You Understand That Objects Remain Constant Even When Cues Change
• 5.9 Receptors in Your Ears Detect Sound Waves
• 5.10 You Perceive Sound Based on Physical Aspects of Sound Waves
• 5.11 Receptors in Your Taste Buds Detect Chemical Molecules
• 5.12 Your Olfactory Receptors Detect Odorants
• 5.13 Receptors in Your Skin Detect Temperature and Pressure
• 5.14 You Detect Pain in Your Skin and Throughout Your Body

4. How Do Sensation and Perception Affect You?
5.1 Your Senses Detect Physical Stimuli, and Your Brain Processes Perception
5.2 There Must Be a Certain Amount of a Stimulus for You to Detect It

5. 5.1 Your Senses Detect Physical Stimuli, and Your Brain
Processes Perception (1)
Sensation: The sense organs’ detection of external
physical stimulus and the transmission of information
about this stimulus to the brain.
Perception: The processing, organization, and
interpretation of sensory signals in the brain; these
processes result in an internal neural representation of
the physical stimulus.

6. 5.1 Your Senses Detect Physical Stimuli, and Your Brain
Processes Perception (2)
From sensation to perception
• Sensory receptors: Sensory organs that detect
physical stimulation from the external world and
change that stimulation into information that can be
processed by the brain.
• Transduction: A process by which sensory
receptors change physical stimuli into signals that
are eventually sent to the brain.

7. 5.1 Your Senses Detect Physical Stimuli, and Your Brain
Processes Perception (3)

8. 5.1 Your Senses Detect Physical Stimuli, and Your Brain
Processes Perception (4)

9. 5.2 There Must Be a Certain Amount of a Stimulus for You to
Detect It (1)
Threshold to detect sensory information
• Absolute threshold: The smallest amount of
physical stimulation required to detect a sensory
input half of the time it is present.
• Difference threshold: The minimum difference in
physical stimulation required to detect a difference
between sensory inputs.
o Weber’s law
o Just-noticeable difference

10. 5.2 There Must Be a Certain Amount of a Stimulus for You to
Detect It (2)

11. 5.2 There Must Be a Certain Amount of a Stimulus for You to
Detect It (3)

12. 5.2 There Must Be a Certain Amount of a Stimulus for You to
Detect It (4)
Sensory adaptation
• A decrease in sensitivity to a constant level of
stimulation

13. How Do You See?
5.3 Sensory Receptors in Your Eyes Detect Light
5.4 You Perceive Color Based on Physical Aspects of Light
5.5 You Perceive Objects by Organizing Visual Information
5.6 When You Perceive Depth, You Can Locate Objects in Space
5.7 Cues in Your Brain and in the World Let You Perceive Motion
5.8 You Understand That Objects Remain Constant Even When Cues Change

14. 5.3 Sensory Receptors in Your Eyes Detect Light (1)
Every time you open your eyes, nearly half your brain
springs into action.

15. 5.3 Sensory Receptors in Your Eyes Detect Light (2)
Focusing light in the eye is an intricate process:
• Light waves pass through the cornea, the thick,
transparent outer layer.
• The light then passes through the pupil, the small
opening that looks like a dark circle.
• The iris, a circular muscle, gives eyes their color and
controls the pupil’s size to determine how much
light enters the eye.
• Behind the iris, muscles change the shape of the
lens, the adjustable, transparent structure behind
the pupil; this structure focuses light on the retina,
resulting in a crisp visual image.

16. 5.3 Sensory Receptors in Your Eyes Detect Light (3)

17. 5.3 Sensory Receptors in Your Eyes Detect Light (4)
Rods and cones
• Retina: The thin inner surface of the back of the eyeball; this
surface contains the sensory receptors.
• Rods: Sensory receptors in the retina that detect light waves
and transduce them into signals that are processed in the brain
as vision. Rods respond best to low levels of illumination and
therefore do not support color vision or detection of fine detail.

18. 5.3 Sensory Receptors in Your Eyes Detect Light (5)
Rods and cones
• Cones: Sensory receptors in the retina that detect
light waves and transduce them into signals that are
processed in the brain as vision. Cones respond best
to higher levels of illumination, and therefore they
are responsible for letting us see color and fine
detail.
o Each retina holds approximately 120 million
rods and 6 million cones. Near the center of the
retina is a small region called the fovea where
cones are densely packed.

19. 5.3 Sensory Receptors in Your Eyes Detect Light (6)
From the eye to the brain
• Information about what the eye has sensed is delivered to the
ganglion cells.
• The axons of each ganglion cell are gathered into a bundle. This
bundle is called the optic nerve.
• There are blind spots in your left and right visual fields, where the
optic nerve exits the retina.
• Half of the axons in the optic nerves cross to the other side of the
brain. The rest of the axons stay on the same side of the brain.
o The point where the axons cross is known as the optic
chiasm.
• The information passes through the thalamus and travels to the
primary visual cortex in the occipital lobes.

20. 5.4 You Perceive Color Based on Physical Aspects of Light (1)
Physical experience of color
• For humans, visible light consists of electromagnetic
waves ranging in length from about 400 to 700
nanometers.
o The amplitude is the height of the light wave
from base to peak; people experience this
quality as brightness.
o The wavelength of the light wave is the distance
from peak to peak. This distance determines
your perception of both hue and saturation.

21. 5.4 You Perceive Color Based on Physical Aspects of Light (2)

22. 5.4 You Perceive Color Based on Physical Aspects of Light (3)
Hue refers to the distinctive
characteristics that place a
particular color in the spectrum.

23. 5.4 You Perceive Color Based on Physical Aspects of Light (4)
Trichromatic theory
• There are three types of cone receptor cells in the
retina that are responsible for color perception.
Each type responds optimally to different but
overlapping ranges of wavelengths.

24. 5.4 You Perceive Color Based on Physical Aspects of Light (5)

25. 5.4 You Perceive Color Based on Physical Aspects of Light (6)
Opponent-process theory
• The idea that ganglion cells in the retina receive
excitatory input from one type of cone and
inhibitory input from another type of cone, creating
the perception that some colors are opposites

26. 5.4 You Perceive Color Based on Physical Aspects of Light (7)

27. 5.5 You Perceive Objects by Organizing Visual Information (1)
The founders of Gestalt
psychology postulated a series
of laws to explain how our
brains group the perceived
features of a visual scene into
organized wholes.

28. 5.5 You Perceive Objects by Organizing Visual Information (2)
Figure and ground
• An object is a figure that is distinct from the
background. The background is referred to as the
ground.

29. 5.5 You Perceive Objects by Organizing Visual Information (3)
Grouping
• The visual system’s organization of features and
regions to create the perception of a whole, unified
object

30. 5.5 You Perceive Objects by Organizing Visual Information (4)

31. 5.5 You Perceive Objects by Organizing Visual Information (5)
Bottom-up processing
• The perception of objects is due to analysis of environmental
stimulus input by sensory receptors; this analysis then
influences the more complex, conceptual processing of that
information in the brain.
Top-down processing
• The perception of objects is due to the complex analysis of prior
experiences and expectations within the brain; this analysis
influences how sensory receptors process stimulus input from
the environment.
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32. 5.6 When You Perceive Depth, You Can Locate Objects in
Space (1)
Binocular depth cues
• Cues of depth perception that arise because people
have two eyes
Monocular depth cues
• Cues of depth perception that are available to each
eye alone

33. 5.6 When You Perceive Depth, You Can Locate Objects in
Space (2)
Binocular depth perception
• Binocular disparity: We use both eyes to perceive
depth through binocular disparity, where each
retina has a slightly different view of the world.

34. 5.6 When You Perceive Depth, You Can Locate Objects in
Space (3)

35. 5.6 When You Perceive Depth, You Can Locate Objects in
Space (4)
Monocular depth perception

36. 5.7 Cues in Your Brain and in the World Allow You to Perceive
Motion (1)
• Motion aftereffects may occur when you gaze at a
moving image for a long time and then look at a
stationary scene.
• The waterfall effect is a momentary impression that
the new scene is moving in the opposite direction
from the moving image.
o If you stare at a waterfall and then turn away,
the new scenery may seem to move upward for
a moment.
o Motion aftereffects are strong evidence that
motion-sensitive neurons exist in the brain.

37. 5.7 Cues in Your Brain and in the World Allow You to Perceive
Motion (2)
Stroboscopic motion
• Movies are made up of still
images, each of which is
slightly different from the one
before it. When the series is
presented fast enough, we
perceive the illusion of
motion pictures.
o This perceptual illusion
is called stroboscopic
motion.

38. 5.8 You Understand That Objects Remain Constant Even
When Cues Change (1)
Object constancy
• Correctly perceiving objects as staying the same in
their size, shape, color, and lightness, across viewing
conditions that yield different physical input to the
eyes

39. How Do You Hear?
5.9 Receptors in Your Ears Detect Sound Waves
5.10 You Perceive Sound Based on Physical Aspects of Sound Waves

40. 5.9 Receptors in Your Ears Detect Sound Waves (1)

41. 5.9 Receptors in Your Ears Detect Sound Waves (2)
From the ear to the brain
• The process of hearing begins when sound waves arrive at the
shell-shaped structure of your outer ear.
o The shell shape of the outer ear increases the ear’s ability
to capture sound waves and then funnel the waves down
the auditory canal.

42. 5.9 Receptors in Your Ears Detect Sound Waves (3)
• Eardrum: A thin membrane that marks the
beginning of the middle ear; sound waves cause the
eardrum to vibrate.
• Cochlea: A coiled, bony, fluid-filled tube in the inner
ear that houses the sensory receptors.
o Running through the center of the cochlea is the
thin basilar membrane.
• Hair cells: Sensory receptors located in the cochlea
that detect sound waves and transduce them into
signals that ultimately are processed in the brain as
sound.

43. 5.10 You Perceive Sound Based on Physical Aspects of Sound
Waves (1)
Loudness and pitch of sounds
• The height of the sound waves is called the
amplitude.
o Amplitude determines our perception of
loudness.
• The distance between peaks of sound waves is the
wavelength.
o The time between the peaks in wavelength is
called the frequency.
o The frequency of the waves determines the
pitch of the sound, from high to low.

44. 5.10 You Perceive Sound Based on Physical Aspects of Sound
Waves (2)

45. 5.10 You Perceive Sound Based on Physical Aspects of Sound
Waves (3)
Temporal and place coding
• Temporal coding: The perception of lower-pitched
sounds is a result of the rate at which hair cells are
stimulated by sound waves of lower frequencies.
• Place coding: The perception of higher-pitched
sounds depends on the point on the basilar
membrane where hair cells are stimulated by sound
waves of varying higher frequencies.

46. 5.10 You Perceive Sound Based on Physical Aspects of Sound
Waves (4)
Localization
• The ear estimates the location of a sound based first
on when the sound arrives and second on the
amplitude, or intensity, of the sound wave.

47. 5.10 You Perceive Sound Based on Physical Aspects of Sound
Waves (5)

48. 5.10 You Perceive Sound Based on Physical Aspects of Sound
Waves (6)
Vestibular sense
• Our vestibular sense allows us
to maintain balance.
o The vestibular sense
uses information from
receptors in structures of
the inner ear called the
semicircular canals.

49. How Are You Able to Taste and Smell?
5.11 Receptors in Your Taste Buds Detect Chemical Molecules
5.12 Your Olfactory Receptors Detect Odorants

50. 5.11 Receptors in Your Taste Buds Detect Chemical Molecules (1)

51. 5.11 Receptors in Your Taste Buds Detect Chemical Molecules (2)
From the mouth to the brain
• Taste buds: Structures, located in papillae on the
tongue, that contain the sensory receptors.
• Papillae: Structures on the tongue that contain
groupings of taste buds.
o The taste information is sent to other brain
regions through a set of nerves, primarily the
facial nerve.
o After processing by the thalamus, the
information is further processed in the primary
gustatory cortex.

52. 5.11 Receptors in Your Taste Buds Detect Chemical Molecules (3)
Five main tastes
• Sweet, sour, salty, bitter, and umami (Japanese for
“savory” or “yummy”) are the five basic taste
qualities.
o As of 2007, umami is the most recently
recognized taste sensation.
• Supertasters are highly aware of flavors and
textures and are more likely than others to feel pain
when eating very spicy foods.
o Supertasters have nearly six times as many taste
buds as normal tasters.

53. 5.11 Receptors in Your Taste Buds Detect Chemical Molecules (4)
Taste preference
• The texture of food affects taste preferences.
• Whether the food causes discomfort affects
preference.
o Spicy chilies
• Cultural influences on food preferences begin in the
womb.

54. 5.12 Your Olfactory Receptors Detect Odorants (1)
When a dog is out for a walk, why does it sniff virtually
every object and creature it encounters?
• The sense of smell, which is also called olfaction, is
the dog’s main way of perceiving the world.
• Dogs have 40 times more olfactory receptors than
humans do.
• Dogs are 100,000 to 1 million times more sensitive
to odors than humans are.
Humans have evolved to rely much more on vision.

55. 5.12 Your Olfactory Receptors Detect Odorants (2)

56. 5.12 Your Olfactory Receptors Detect Odorants (3)
From the nose to the brain
• Olfactory epithelium: A thin layer of tissue, deep
within the nasal cavity, containing the olfactory
receptors; these sensory receptors produce information
that is processed in the brain as smell.
o Chemical molecules are called odorants.
• Olfactory bulb: A brain structure above the olfactory
epithelium in the nasal cavity; from this structure, the
olfactory nerve carries information about smell to parts
of the brain, including the primary olfactory cortex.
o Unlike all other forms of sensory information, smell
signals bypass the thalamus.

57. 5.12 Your Olfactory Receptors Detect Odorants (4)
Variety of smells
• There are thousands of olfactory receptors in the
olfactory epithelium, but there are about 350 types
(Miller, 2004).
o Each receptor responds to different odorants.
o According to a recent estimate, humans can
distinguish more than a trillion odorants
(Bushdid, Magnasco, Vosshall, & Keller, 2014).

58. 5.12 Your Olfactory Receptors Detect Odorants (5)
Smell perception
• Information about whether a smell is pleasant or
unpleasant is processed in the brain’s prefrontal
cortex.
• The smell’s intensity is processed in the amygdala, a
brain area involved in emotion and memory.
o Most people are pretty bad at identifying odors
by name.
o Women tend to be better at detecting smells
than men are.

59. How Do You Feel Touch and Pain?
5.13 Receptors in Your Skin Detect Temperature and Pressure
5.14 You Detect Pain in Your Skin and Throughout Your Body

60. 5.13 Receptors in Your Skin Detect Temperature and Pressure (1)
From the skin to the brain
• Warm receptors: Sensory receptors in the skin that
detect the temperature of stimuli and transduce it into
information processed in the brain as warmth.
• Cold receptors: Sensory receptors in the skin that
detect the temperature of stimuli and transduce it into
information processed in the brain as cold.
• Pressure receptors: Sensory receptors in the skin that
detect tactile stimulation and transduce it into
information processed in the brain as different types of
pressure on the skin.
• Touch information travels first through the thalamus
and then to the primary somatosensory cortex, which
processes the information.

61. 5.13 Receptors in Your Skin Detect Temperature and Pressure (2)

62. 5.13 Receptors in Your Skin Detect Temperature and Pressure (3)
Perception of touch
• Penfield discovered that electrical stimulation of the
primary somatosensory cortex could evoke the
perception of touch in different regions of the body.
o For the most sensitive regions of the body, such
as the lips and fingers, a great deal of the cortex
is dedicated to processing touch.

63. 5.13 Receptors in Your Skin Detect Temperature and Pressure (4)
Kinesthetic Sense
• Our Kinesthetic sense tells us
how our body and limbs are
positioned in space.
o Kinesthetic sensations
come from receptors in
muscles, tendon, and
joints.

64. 5.14 You Detect Pain in Your Skin and Throughout Your Body (1)
Two types of pain receptors
• Fast fibers: Sensory receptors in the skin, muscles,
organs, and membranes around both bones and
joints; these myelinated fibers quickly convey
intense sensory input to the brain, where it is
perceived as sharp, immediate pain.
• Slow fibers: Sensory receptors in the skin, muscles,
organs, and membranes around both bones and
joints; these unmyelinated fibers slowly convey
intense sensory input to the brain, where it is
perceived as chronic, dull, steady pain.

65. 5.14 You Detect Pain in Your Skin and Throughout Your Body (2)
Gate control theory
• We experience pain when pain receptors are
activated and a neural “gate” in the spinal cord
allows the signals through to the brain (Melzack &
Wall, 1982).
• These ideas were radical in that they depict pain as
a perceptual experience within the brain rather
than simply a response to nerve stimulation.

66. 5.14 You Detect Pain in Your Skin and Throughout Your Body (3)
Controlling pain
• Distraction can reduce your perception of pain.
o Listening to music is an extremely effective way
to reduce postoperative pain, perhaps because it
helps patients relax.