The document discusses basic principles of sensation and perception including: - Bottom-up and top-down processing in sensory analysis. - Transduction which converts stimulus energies into neural impulses. - Absolute and difference thresholds and how they operate in processing sensory information. - Sensory adaptation which diminishes sensitivity with constant stimulation across the senses. - Perceptual sets which influence perception through expectations and experiences.

1. PART 7
© T.G. Lane 2018
1 BASIC PRINCIPLES OF SENSATION AND PERCEPTION
SECTIONS
SENSATION AND PERCEPTION
Ѱ
7
Psychology, Twelfth Edition (Myers, D. G.)
2 VISION
3 THE OTHER SENSES

2. LEARNING OBJECTIVES
• Discuss and identify differences between bottom-up and
top-down-processing
• Explain the process of transduction through use of sensory
systems
• Discuss how absolute and difference thresholds operate when
processing sensory information
• Identify examples of different types of perceptual sets
• Discuss how the human eye processes light energy into visual
information
SENSATION AND PERCEPTIONPART7
© T.G. Lane 2018

3. LEARNING OBJECTIVES
• Discuss how Gestalt psychologists understand perceptual
organization, and how figure-ground and grouping
principles contribute to human perceptions
• Discuss how humans perceive depth perception, motion,
perception, and perceptual constancy
• Discuss how perceptual adaptation works
• Discuss how the gate-control theory helps to explain pain
• Discuss how pain can be examined using psychology’s three
levels of analysis
SENSATION AND PERCEPTIONPART7
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4. SENSATION AND PERCEPTIONPART7
SECTION
AND PERCEPTION
BASIC PRINCIPLES OF SENSATION
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5. 1
Test Your Brain:
Perception
Video
SENSATION AND PERCEPTIONPART7:SENSATIONANDPERCEPTION
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6. SENSING THE WORLD: SOME BASIC PRINCIPLES1
What are sensation and perception? What do we mean by
bottom-up processing and top-down processing?
1:
Sensation and perception blend into one continuous process.
• sensation: the process by which
our sensory receptors and
nervous system receive and
represent stimulus energies from
the environment
• perception: the process of
organizing and interpreting
sensory information, enabling
us to recognize meaningful
objects and events
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© T.G. Lane 2018

7. SENSING THE WORLD: SOME BASIC PRINCIPLES1
Sensory analysis in humans occurs through two ways:
bottom-up processing and top-down processing.
• bottom-up processing: analysis
that begins with the sensory
receptors and works up to the
brain’s integration of sensory
information (i.e. it used to fill in
the gaps)
• top-down processing: information
processing guided by higher level
mental processes, as when one
conducts perceptions drawing on
one’s experiences and expectations
(i.e. what is anticipated)
Video Clip
Video Clip
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8. SENSING THE WORLD: SOME BASIC PRINCIPLES1
Describe how bottom-up and top-
down processing are used here.
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9. 2
TRANSDUCTION
What three steps are basic to all humans’ sensory systems?2:
• receive sensory stimulation, often
using specialized receptor cells
• transfer that stimulation into neural
impulses
• deliver the neural information to
your brain
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10. 2
TRANSDUCTION
The process of converting one form of energy into another that
your brain can use is called transduction.
• transduction: conversion of one form of energy into
another; in sensation, the transforming of stimulus
energies, such as sights, sounds, and smells, into neural
impulses our brain can interpret
SENSING THE WORLD: SOME BASIC PRINCIPLES
Chemical
Molecules
Chemical
Molecules
Sound
Waves
Light
Energy
Pressure/ Temperature/
Pain
Stimuli for the Human Senses
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11. SENSING THE WORLD: SOME BASIC PRINCIPLES1
• Absolute thresholds can vary with age (e.g.
as humans get older, recognition of high
pitch sounds gets lower).
absolute threshold: the minimum stimulation needed
to detect a particular stimulus 50 percent of the time
(awareness of faint stimuli)
THRESHOLDS
What are the absolute and difference thresholds, and do stimuli
below the absolute threshold have any influence?
3:
Absolute Threshold
• At slightly below the absolute threshold, one
can still detect a stimulus some of the time.
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12. SENSING THE WORLD: SOME BASIC PRINCIPLES1
• subliminal: below one’s
absolute threshold for
conscious awareness
THRESHOLDS
Subliminal Stimulation
Some entrepreneurs aim to penetrate unconscious awareness through
the use of subliminal messaging in order to produce suggestive powers.
• At slightly below the
absolute threshold, one
can still detect a stimulus
some of the time.
VideoClipVideoClip
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13. SENSING THE WORLD: SOME BASIC PRINCIPLES1
THRESHOLDS
Subliminal Stimulation
Under certain conditions, one can be affected by stimuli so weak
that it is unnoticed. One example of this is through priming.
priming: the activation, often
unconsciously, of certain assoc-
iations, thus predisposing one's
perception, memory, or response
Example: participants that are asked
to make sentences using negative
words (masking stimulus)– later
results in rude behavior)
VideoClipVideoClip
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14. SENSING THE WORLD: SOME BASIC PRINCIPLES1
THRESHOLDS
Difference Threshold
To function effectively, humans need thresholds low enough to
allow them to detect important sights, sounds, textures, tastes, and
smell; this concept is called the difference threshold.
• difference threshold: the
minimum differences between
two stimuli required for detection
50 percent of the time; also
termed as the just noticeable
difference
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15. SENSING THE WORLD: SOME BASIC PRINCIPLES1
SENSORY ADAPTATION
What is the function of sensory adaptation?4:
• A person’s ability to withstand an unpleasant stimuli (e.g. odor)
involves sensory adaptation.
• sensory adaptation: diminished sensitivity as a
consequence of constant stimulation
• Sensory adaptation can
occur through all five of
the human senses (e.g.
fixed eyesight results in
fading vision); the
human senses require
being stimulated and
excited.
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16. SENSING THE WORLD: SOME BASIC PRINCIPLES1
PERCEPTUAL SET
How do our experiences, contexts, emotions, and motivation
influence our perceptions?
5:
Through experience, we come to expect certain results; those
expectations may give us a perceptual set.
perceptual set: a mental predisposition to perceive one
thing and not another
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17. SENSING THE WORLD: SOME BASIC PRINCIPLES1
PERCEPTUAL SET
Hearing
Cheer Up vs. Geer Up
Taste
Taste Comparisons
Sight Baby Girl vs. Baby Boy
Colors
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18. SENSING THE WORLD: SOME BASIC PRINCIPLES1
A given stimulus may trigger radically different perceptions, partly
because of our differing set, but also because of the immediate
context.
CONTEXT EFFECTS
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19. SENSATION AND PERCEPTIONPART7
SECTION
VISION
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20. VISION2
THE EYE
The Stimulus Input: Light Energy
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21. VISION2
THE RETINA
• retina: the light sensitive membrane at the back
of the eye containing the receptor rods and
cones plus layers of neurons that begin the
processing of visual information
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22. VISION2
THE RETINA
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23. VISION2
THE RETINA
Parts of the retina include the rods, cones, and optic nerve.
• rods: retinal receptors that detect black, white,
and gray; necessary for peripheral and twilight
vision, when cones don’t respond
• cones: retinal receptor cells that are
concentrated near the center of the
retina and that function in daylight or in
well-lit conditions; the cones detect fine
detail and give rise to color sensations
• optic nerve: the nerve that carries neural impulses
from the eye to the brain (i.e. where the thalamus
will receive and distribute the information)
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24. VISION2
THE RETINA
When an image is focused on the retina, that image is casted
upside down. The retina’s millions of receptor cells convert
particles of light energy into neural impulses and forward those to
the brain (causing the image to appear right-side up).
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25. VISION2
VISUAL INFORMATION PROCESSING
How does the brain processes visual information?6:
• At the entry level, the retina
processes information before
routing it via the thalamus to
the brain’s cortex.
• The retina’s neural layers
help to encode and analyze
the sensory information
from its rods and cones.
• Information is then passed on
through ganglion cells,
through axons making up the
optic nerve, to one’s brain
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26. VISION2
VISUAL INFORMATION PROCESSING
• There is a certain
temporal lobe region of
the brain that enables
humans to perceive
faces and if damaged
one might not recognize
other forms or objects.
Feature Detection
• feature detection: nerve cells in the brain that respond
to specific features of the stimulus, such as shape, angle,
or movement
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27. VISION2
VISUAL INFORMATION PROCESSING
• The human brain is capable of parallel processing which
allows for being able to do many things at once.
Parallel Processing
• parallel processing: the processing of
many aspects of a problem
simultaneously; the brain’s natural
mode of information processing for
many functions, including vision;
contrasts with the step-by-step
(serial) processing of most computers
and of conscious problem solving.
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28. VISION2
VISUAL INFORMATION PROCESSING
Features of Parallel Processing
The brain divides a visual scene into subdimensions, such as color,
movement, form, and depth.
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29. VISION2
VISUAL INFORMATION PROCESSING
Color Vision
• Color, like all aspects of
vision, resides not in the
object but in the theater of
the human brain, as evident
by one dreaming in color.
Where does color reside?7:
• For about 1 person in 50
(usually male), are color
deficient.
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30. PERCEPTUAL ORGANIZATION2
How did the Gestalt psychologists understand perceptual
organization?
9:
• German psychologists noticed that
when given a cluster of sensations,
people tend to organize them into a
gestalt in order to form meaningful
interpretations.
• gestalt: an organized whole; gestalt
psychologists emphasized our
tendency to integrate pieces of
information into meaningful wholes
• The idea is that the whole is greater than the
sum of its parts.
VISUAL ORGANIZATION
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31. PERCEPTUAL ORGANIZATION2
FORM PERCEPTION
Figure and ground
First, the eye-brain system
distinguishes any object
(figure) from its area
surroundings (ground)
Humans organize stimuli into
a figure seen against a ground
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32. PERCEPTUAL ORGANIZATION2
FORM PERCEPTION
Grouping
Second, the eye-brain system must also
organize the figure into a meaningful form
• To bring order and form to basic
sensations, the human mind follow
certain rules for grouping stimuli
together.
• grouping: the perceptual
tendency to organize stimuli
into coherent groups (helps to
construct reality)
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33. PERCEPTUAL ORGANIZATION2
FORM PERCEPTION
Grouping Examples
proximity:
humans group
nearby figures
together
similarity:
humans group
similar figures
together
continuity:
humans perceive
smooth, continuous
patterns rather than
discontinuous ones
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34. PERCEPTUAL ORGANIZATION2
FORM PERCEPTION
Grouping Examples
closure:
humans fill in gaps to create a
complete, whole object
connectedness:
humans perceive certain
stimuli in single units or sets
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35. PERCEPTUAL ORGANIZATION2
DEPTH PERCEPTION
How do we see the world in three dimensions.10:
Depth perception enables humans to
estimate an object’s distance from
themselves.
• depth perception: the ability to see
objects in three dimensions although
the images that strike the retina are
two-dimensional; allow humans to
judge distance
The human brain constructs three dimensional
perceptions using information supplied by one
or both eyes
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36. PERCEPTUAL ORGANIZATION2
MOTION PERCEPTION
How do we perceive motion?11:
• The human brain can perceive continuous movement in a rapid series
of slightly varying images (e.g. film/sideshow)
• The human brain normally
computes motion based partly
on its assumption that
shirking objects
retreating/disappearing (not
getting smaller) and enlarging
objects are approaching; this
is an imperfect perception
(e.g. fast vs. slow objects)Video Clip
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37. PERCEPTUAL ORGANIZATION2
PERCEPTUAL CONSTANCY
• perceptual constancy: perceiving
objects as un-changing (having
consistent shapes, size, lightness, and
color) even as illumination and retinal
images change – this is a top-down
process
Humans must be able to recognize
objects without being deceived by
changes in their shape, size, brightness,
or color– an ability called perceptual
constancy.
How do perceptual constancies help us organize our sensations
into meaningful perceptions?
12:
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38. PERCEPTUAL ORGANIZATION2
PERCEPTUAL CONSTANCY
Color Constancy
color constancy:
perceiving familiar
objects as having
consistent color,
even if changing
illumination alters
the wavelengths
reflected by the
object
Humans perceive
objects not in
isolation but in
their environ-
mental context
(comparisons
govern our
perceptions)
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39. PERCEPTUAL ORGANIZATION2
PERCEPTUAL CONSTANCY
Shape and Size Constancies
• Sometimes an object whose
actual shape cannot change
seems to change shape with
the angle of one’s view.
• Humans perceive the form of
familiar objects as constant
even while our retinal image
of it changes; this is an
example of shape constancy
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40. PERCEPTUAL ORGANIZATION2
VISUAL INTERPRETATION
Humans have the ability to change their visual input in order to
make the world seem normal through the use of perceptual
adaptation.
• perceptual adaptation: in
vision, the ability to adjust to
an artificially displaced or
even inverted visual field
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41. SENSATION AND PERCEPTIONPART7
SECTION
THE OTHER SENSES
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42. PERCEPTUAL ORGANIZATION3
PAIN
How can we best understand pain?13:
• Pain is one’s body way of telling
them that something is wrong;
pain orders one to change their
behavior
• Individual pain sensitivity varies
depending on genes, physiology,
experience, attention, and
surrounding culture
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43. PERCEPTUAL ORGANIZATION3
PAIN
There is no one type of stimulus that triggers pain (as light
triggers vision).
• there are different nociceptors—
sensory receptors that detect
hurtful temperatures, pressure,
or chemicals
• gate-control theory: the
theory that the spinal cord
contains a neurological
“gate” that blocks pain
signals or allows them to
pass on to the brain
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44. PERCEPTUAL ORGANIZATION3
PAIN
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