Transcript Sensation and Perception

Psychology, 4/e by Saul Kassin
CHAPTER 3:
Sensation and Perception
Sensation and Perception
Measuring the Sensory Experience
Sensation
Perception
Extrasensory Perception
Psychology, 4/e by Saul Kassin
©2004 Prentice Hall
Sensation and Perception
 Sensation

The processes by which our sense organs
receive information from the environment.
 Transduction

The process by which physical energy is
converted into sensory neural impulses.
 Perception

The processes by which people select,
organize, and interpret sensations.
Psychology, 4/e by Saul Kassin
©2004 Prentice Hall
Sensation & Perception Processes
Psychology, 4/e by Saul Kassin
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Measuring Sensory Experience
Research and Theory
 Psychophysics

The study of the relationship between
physical stimulation and subjective
sensations.
 Signal-Detection Theory

The theory that detecting a stimulus is
jointly determined by the signal and the
subject’s response criterion.
Psychology, 4/e by Saul Kassin
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Measuring Sensory Experience
Thresholds
 Absolute Threshold

The smallest amount of stimulation that can
be detected.
 Just Noticeable Difference (JND)

The smallest amount of change in a stimulus
that can be detected.
Psychology, 4/e by Saul Kassin
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Measuring Sensory Experience
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
 Taste: 1 teaspoon sugar in 2 gallons of water
 Touch: The wing of a bee on your cheek, dropped
from 1 cm
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Sensation
 Vision
 Hearing
 Other Senses
 Keeping the Signals Straight
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Vision
The Electromagnetic Spectrum
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Vision
Structures of the Human Eye
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Vision
Structures of the Human Eye
 Cornea

Clear outer membrane that bends light to
focus it in the eye.
 Pupil

The hole in the iris through which light
passes.
 Lens

The structure that focuses light on the retina.
Psychology, 4/e by Saul Kassin
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Vision
The Retina
•The rear
of the eye
where
rods and
cones
convert
light into
neural
impulses.
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Vision
Visual Pathways
Optic Nerve
•Pathway that
carries visual
information
from the eyeball
to the brain.
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Vision
Hubel & Wiesel’s Experiment
 Some cells in the visual cortex respond only to
certain types of visual information, for example, a
diagonal line moving up and down.
 These cells are called feature detectors.
Psychology, 4/e by Saul Kassin
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Vision
Trichromatic Theory
 T. Young (1802) & H.
von Helmholtz (1852)
both proposed that the
eye detects 3 primary
colors: red, blue, &
green.
 All other colors can be
derived by combining
these three.
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Vision
Afterimage
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Vision
The Color Wheel
 Spectral colors vary
from violet-blue to red
 470 to 700 nanometer
wavelength
 Opponent colors are
directly across from each
other on the wheel.
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Vision
Test of Color Deficiency
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Vision
Opponent-Process Theory
Color vision is derived from three pairs
of opposing receptors. The opponent
colors are blue and yellow, red and
green, and black and white.
 Theory explains afterimages and color
deficiency.

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Hearing
The Human Ear
Audition
•The
sense of
hearing
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Hearing
Auditory Localization
The ability to judge
from which direction a
sound is coming
 Sounds from different
directions are not
identical as they arrive at
left and right ears.
 The brain calculates a
sound’s location by using
differences in timing and
intensity.

Psychology, 4/e by Saul Kassin
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Hearing
Hearing Disabilities
 Conduction Hearing Loss

Caused by damage to the eardrum or bones
in the middle ear.
 Sensorineural Hearing Loss

Caused by damage to the structures of the
inner ear.
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Hearing
Common Sounds and the Noise They Produce
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Other Senses
Olfactory System
•Structures
responsible
for the
sense of
smell
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Other Senses
Nets of taste-receptor
Taste
cells
This is a photograph of
tongue surface (top),
magnified 75 times.
10,000 taste buds line the
tongue and mouth.
Children have more taste
buds than adults do.
There are four primary
tastes: sweet, salty, sour,
and bitter.
Psychology, 4/e by Saul Kassin


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
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Buds
Other Senses
Sensitivity to Touch
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Other Senses
The Thermal Grill
Temperature
 When a person grasps
two braided water pipes
– one with cold water
running through it and
one with warm water –
the sensation is “burning
hot” and painful.
 There are two separate
pathways for warmth and
cold.
Psychology, 4/e by Saul Kassin
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Other Senses
Pain
 Gate-control Theory

Theory that the spinal cord contains a
neurological “gate”that blocks pain signals
for the brain when flooded by competing
signals.
 Psychological control

Mind over sensation, distraction
Psychology, 4/e by Saul Kassin
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Other Senses
Coordination
 Kinesthetic System

Structures distributed throughout body that
sense position and movement of body parts.
 Vestibular System

The inner ear and brain structures that
afford a sense of equilibrium.
Psychology, 4/e by Saul Kassin
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Keeping the Signals Straight
 Synesthesia

Rare condition in which stimulation in one
sensory modality triggers sensations in
another sensory modality.
 Each sensory system designed to operate
separately from the others.
 Selective Adaptation

A decline in sensitivity to a stimulus as a
result of constant exposure.
Psychology, 4/e by Saul Kassin
©2004 Prentice Hall
Perception
Perceptual Organization
Perceptual Constancies
Depth and Dimension
Perceptual Set
The World of Illusions
Perceptual Organization
Reversible Figures

Drawings that one can
perceive in different
ways by reversing
figure and ground.
 Gestalt Psychology

School of thought
rooted in the idea that
the whole is different
from the sum of its
parts.
Psychology, 4/e by Saul Kassin
©2004 Prentice Hall
Perceptual Organization
Gestalt Laws of Grouping
 Proximity

Seeing 3 pair of lines in A
 Similarity

Seeing columns of orange
and red dots in B
 Continuity

Seeing lines that connect 1
to 2 and 3 to 4 in C
 Closure

Seeing a horse in D
Psychology, 4/e by Saul Kassin
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Perceptual Organization
Identifying Objects
 Geons (geometric
icons) are simple 3D
component shapes.
 A limited number are
stored in memory.
 Geons are combined
to identify essential
contours of objects.
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Perceptual Constancies
 Size Constancy

The tendency to view an object as constant
in size despite changes in the size of the
retinal image.
 Shape Constancy

The tendency to see an object as keeping its
form despite changes in orientation.
Psychology, 4/e by Saul Kassin
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Perceptual Constancies
The Ames Room
 A specially-built room that
makes people seem to
change size as they move
around in it
 The room is not a
rectangle, as viewers
assume it is.
 A single peephole prevents
using binocular depth cues.
Psychology, 4/e by Saul Kassin
©2004 Prentice Hall
Perceptual Constancies
Shape Constancy
 Even though these images cast shadows of
different shapes, they still are seen as round.
Psychology, 4/e by Saul Kassin
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Depth and Dimension
 Depth Perception

The use of visual cues to estimate depth and
distance.
 Convergence

A binocular cue involving the turning
inward of the eyes as an object gets closer.
 Binocular Disparity

A binocular cue whereby the closer an object
is, the more different the image is in each
retina.
Psychology, 4/e by Saul Kassin
©2004 Prentice Hall
Depth and Dimension
Monocular Depth Cues

Distance cues that enable the perception of
depth with one eye.
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Relative Image Size
Texture Gradient
Linear Perspective
Interposition
Atmospheric Perspective
Relative Elevation
Familiarity
Psychology, 4/e by Saul Kassin
©2004 Prentice Hall
Depth and Dimension
The Visual Cliff
 Devised by Eleanor
Gibson and Richard Walk
to test depth perception in
infants and animals.
 Provides visual illusion of
a cliff.
 Caregiver stands across
the gap.
 Babies are not afraid until
about the age they can
crawl.
Psychology, 4/e by Saul Kassin
©2004 Prentice Hall
Perceptual Set
 What is seen in the center figures depends on the
order in which one looks at the figures:
 If scanned from the left, a man’s face is seen.
 If scanned from the right, a woman’s figure is
seen.
Psychology, 4/e by Saul Kassin
©2004 Prentice Hall
Perceptual Set
Context Effects
 The same physical
stimulus can be
interpreted differently
depending on
perceptual set, e.g.,
context effects.
 When is the middle
character the letter B
and when is it the
number 13?
Psychology, 4/e by Saul Kassin
©2004 Prentice Hall
The World of Illusions
The Müller-Lyer Illusion

Illusion in which
the perceived
length of a line is
altered by the
position of other
lines that enclose it
Psychology, 4/e by Saul Kassin
©2004 Prentice Hall
The World of Illusions
The Ponzo Illusion
Illusion in which the
perceived line length
is affected by linear
perspective cues.
 Side lines seem to
converge
 Top line seems farther
away


But the retinal images
of the red lines are
equal.
Psychology, 4/e by Saul Kassin
©2004 Prentice Hall
Extrasensory Perception
The Case for ESP
The Case against ESP
The Continuing Controversy
The Case for ESP
 Extrasensory Perception (ESP)


The ability to perceive something without
ordinary sensory information.
This has not been scientifically demonstrated.
 Parapsychologists distinguish between three
types of ESP:



Telepathy – Mind-to-mind communication
Clairvoyance – Perception of remote events
Precognition – Ability to see future events
Psychology, 4/e by Saul Kassin
©2004 Prentice Hall
The Case against ESP
ESP Cards
 J. B. Rhine conducted many experiments on ESP
using stimuli such as these.
 Rhine believed that his evidence supported the
existence of ESP, but his findings were flawed..
Psychology, 4/e by Saul Kassin
©2004 Prentice Hall
The Continuing Controversy
 The ganzfield procedure
 Researchers disagree about the reliability of
studies done to replicate the ganzfield test.
 Visit www.randi.org/ for information about
the James Randi Educational Foundation’s
million-dollar paranormal challenge.
Psychology, 4/e by Saul Kassin
©2004 Prentice Hall