Sensation and Perception
Chapter 3
LO 3.1 Sensation and the central nervous system
Sensation
• Sensation - the activation of receptors in the various
sense organs.
• Sensory receptors - specialized forms of neurons.
• Sense organs:
• eyes
• ears
• nose
• skin
• taste buds
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Eye Sensory Receptors
Ear Sensory Receptors
Nose Sensory Receptors
Skin Sensory Receptors
Sensation and Perception
Stimulus
energy
•Heat
•Light
Sensory receptor
•Eyes
•Nose
•Skin
Sensation
Neural
impulse
Brain
•Visual
•Olfactory
Perception
LO 3.1 Sensation and the central nervous system
Sensory Thresholds
• Absolute threshold - smallest amount of energy needed
for a person to consciously detect a stimulus (50% of
time)
• Just noticeable difference smallest difference between
two stimuli that is detectable (50% of time)
•
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LO 3.1 Sensation and the central nervous system
Habituation and Sensory
Adaptation
• Habituation - tendency of the brain to stop attending
to constant, unchanging information.
• Sensory adaptation - tendency of sensory receptor
cells to become less responsive to a stimulus that is
unchanging.
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Light
Amplitude
Wavelength
LO 3.2
What is light
Psychological Aspects to Light
• Brightness - amplitude
of the wave; higher
waves brighter; lower
waves dimmer.
Saturation
Color
• Color - length of the
wave; long
wavelengths red;
short waves blue
• Saturation - purity of
the color people see
Brightness
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LO 3.3
How eyes see and see color
Structure of the Eye
Cornea
Pupil
• Cornea – clear membrane that
covers surface of eye; protects
eye and focuses most of light
coming into eye.
• Pupil – hole through which light
from the visual image enters
eye.
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LO 3.3 How eyes see and see color
Structure of the Eye
• Iris - round muscle; can change
the size of the pupil, letting more
or less light into the eye; helps
focus the image.
• Lens – suspended by muscles;
finishes the focusing process
begun by the cornea.
Lens
Iris
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LO 3.3 How eyes see and see color
Retina, Rods, and Cones
• Photoreceptors that
respond to various light
waves
Retina
• Rods – receptors
responsible for noncolor vision and
sensitivity to dim light.
• Cones – receptors
responsible for color
vision and sharpness of
vision.
Cone
Optic nerve
Rod
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Visual Field of left eye
Optic
nerve
Visual field of right eye
Optic chasm
Primary visual area
LO 3.3 How eyes see and see color
Color Vision
• Trichromatic theory - theory of
color vision that proposes three
types of cones: red, blue, and
green.
• Opponent-process theory theory of color vision that
proposes four primary colors with
cones arranged in pairs: red and
green, blue and yellow
Or
Or
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LO 3.3 How eyes see and see color
Color Blindness
• Monochrome colorblindess - either have no cones or
have cones that are not working at all.
• Red-green colorblindess - either the red or the green
cones are not working.
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LO 3.4
Sound
• Amplitude –volume
(how soft or loud a
sound is).
• Wavelength –
frequency or pitch
• Purity –timbre (a
richness in the tone
of the sound).
•
What is sound
Amplitude
Wavelength
Quieter
Louder
http://www.youtube.com/watch
?v=2RkaD9nAv34.
Deeper pitch
Higher pitch
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LO 3.4 What is sound
Structure of the Ear
• Auditory canal - short
tunnel that runs from
the pinna to the
eardrum
• Eardrum - thin section
of skin that tightly
covers the opening into
Eardrum
the middle part of the
Auditory canal
ear
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Structure of the Ear
• When sound waves hit the eardrum, it
vibrates and causes three tiny bones in
the middle ear to vibrate.
• Hammer
• Anvil
• Stirrup
Hammer
Hammer
Stirrup
Anvil
LO 3.4 What is sound
Structure of the Ear
• Cochlea - snail-shaped structure of the inner ear that
is filled with fluid.
• Organ of Corti – rests in the basilar membrane;
contains receptor cells for sense of hearing.
Organ of Corti
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Structure of the Ear
http://www.youtube.com/watch?v=
7a2aoZeZhZ8&feature=related
http://www.youtube.com/watch?v=
8wgfowbbTz0&feature=related
Auditory nerve - bundle
of axons from the hair
cells in the inner ear;
receives neural
message from the
organ of Corti.
Auditory
nerve
LO 3.4 What is sound
Theories of Pitch
• Pitch - frequency of the sound waves; higher
frequencies are perceived as higher pitches.
• Place theory - states that different pitches are
experienced by the stimulation of hair cells in
different locations on the organ of Corti.
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LO 3.4 What is sound
Theories of Pitch
• Frequency theory - states that pitch is related to the
speed of vibrations in the basilar membrane.
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LO 3.6 Senses of taste and smell
Taste
• Taste buds – taste receptor cells in mouth;
responsible for sense of taste
• Gustation - the sensation of a taste.
• Five Basic Tastes:
• Sweet
• Sour
• Salty
• Bitter
• “Brothy”
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LO 3.6 Senses of taste and smell
Taste
Bitter
Taste
pore
Receptor
cell
Sour
Salty
Sweet
Nerve
fiber
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LO 3.6 Senses of taste and smell
Smell
• Olfaction (olfactory
sense) – sense of
smell.
• Olfactory bulbs areas of the brain that
receive information
from the olfactory
receptor cells.
Receptor
Olfactory
bulb
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LO 3.7 Touch, pain, motion and balance
Somesthetic Senses
• Somesthetic senses - the
skin senses, the kinesthetic
sense, and the vestibular
senses.
1. Skin senses - the sensations
of touch, pressure,
temperature, and pain.
1. Kinesthetic sense - sense of
the location of body parts in
relation to the ground and
each other.
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LO 3.7 Touch, pain, motion and balance
Somesthetic Senses
3. Vestibular senses the sensations of
movement, balance
• Sensory conflict
theory in which the
information from
the eyes conflicts
with the information
from the vestibular
senses resulting in
dizziness.
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LO 3.8 Perception and perceptual constancies
Perception and Constancies
• Perception - the method by which the
sensations experienced at any given
moment are interpreted and organized in
some meaningful fashion.
•
http://www.youtube.com/watch?v=L3AgO6H0H98
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Constancy
• Size constancy - the
tendency to interpret an
object as always being
the same actual size,
regardless of its
distance.
Constancy
• Shape constancy - the
tendency to interpret
the shape of an object
as being constant, even
when its shape changes
on the retina.
Constancy
• Brightness constancy –
the tendency to
perceive the apparent
brightness of an object
as the same even when
the light conditions
change.
LO 3.9 Gestalt principles of perception
Gestalt Principles
• Figure–ground - the tendency to perceive
objects as existing on a background.
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Gestalt Principals
• Reversible figures - visual
illusions in which the figure and
ground can be reversed.
Gestalt Principals
LO 3.9 Gestalt principles of perception
Gestalt Principles
Similarity
Proximity
Continuity
Closure
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LO 3.10 Perceiving the world in three dimensions
Development of Perception
• Depth perception - the ability to perceive the world in
three dimensions
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LO 3.10 Perceiving the world in three dimensions
Monocular Cues
• Monocular cues (pictorial depth cues) – cues for
perceiving depth based on one eye only.
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LO 3.10 Perceiving the world in
three dimensions
Monocular cues
Linear Perspective
Texture gradient
Areal perspective
Relative size
Binocular Cues
• Binocular cues - cues for
perceiving depth based on
both eyes.
1. Convergence - the
rotation of the two eyes
to focus on a single
object, resulting in
greater convergence for
closer objects and
lesser convergence if
objects are distant.
Focal
point
Left
Right
Far
Near
Binocular Cues
• Binocular disparity - the difference in images
between the two eyes, which is greater for objects
that are close and smaller for distant objects.
LO 3.11 Visual illusions
Perceptual Illusions
Müller-Lyer illusion
LO 3.11 Visual illusions
Perceptual Illusions
Moon Illusion
LO 3.11 Visual illusions and other factors influencing perception
Perceptual Illusions
• Illusions of Motion:
• Stroboscopic motion - seen in motion pictures, in
which a rapid series of still pictures will appear to
be in motion.
LO 3.11 Visual illusions and other factors influencing perception
Factors that Influence Perception
• Perceptual expectancy- the tendency to perceive
things a certain way because previous experiences
or expectations influence those perceptions.