Sensation and Perception Chapter 3 Sensation is the activation of receptors in the sense organs like eyes, ears, nose, skin, and taste buds. This physical sensory information is transmitted to the brain via neurons through a process called transduction. The brain then interprets this sensory information through perception. Perception involves organizing and making sense of sensations. [/SUMMARY]

1. Sensation and Perception
Chapter 3

2. Sensation
• Sensation - the activation of receptors in
the various sense organs.
• Sensory receptors - specialized forms of
neurons.
• Sense organs:
• Eyes – Visual Sensation
• Ears – Auditory Sensation
• Nose- Olfactory Sensation
• Skin – Tactile Sensation
• Taste buds (tongue) – Gustatory
Sensation

3. So where do vision and
hearing (& the other senses)
• The Brain!happen?
• The physical energy in
the environment is
detected by the eyes,
ears, etc. but we can‘t
see, hear, etc. until the
brain interprets them—
i.e., makes sense of
them. So in a way, we
see, hear, smell, etc. in
our brains!

4. Transduction
• Transforming
signals into neural
impulses.
• Information goes
from the senses to
the thalamus , then
Remember Ethan in Sky High. He
to the various areas changes his body to slime. Solid
form to liquid form. Change from
in the brain. one form of energy to another.
Transduction is transforming physical
energy into neural impulses

6. Sensory Thresholds
• Just noticeable difference
or the difference
threshold) - the smallest
difference between two
stimuli that is detectable
50 percent of the time.

7. Sensory Thresholds
• Absolute threshold - the smallest
amount of energy needed for a
person to consciously detect a
stimulus 50 percent of the time it
is present.

8. Subliminal Sensation
• Subliminal stimuli - stimuli that are below
the level of conscious awareness.
• Just strong enough to activate the sensory
receptors but not strong enough for people
to be consciously aware of them.
• Limin - ―threshold‖
• Sublimin - ―below the threshold.‖
• Subliminal perception – process by why
subliminal stimuli act upon the
unconscious mind, influencing behavior.

9. Perception of Minimal Stimuli
• Subliminal Perception
• The concept of subliminal perception is
well known to the general public.
• Subliminal perception is the idea that a stimulus
can influence behavior even when it is so weak
or brief that we do not perceive it consciously.
• There is concern that subliminal perception can
powerfully manipulate human behavior.

10. Perception of Minimal Stimuli
• What does ―subliminal‖ mean?
• When the term ―subliminal‖ is used, it
refers to the quality of being ―below the
(sensory) threshold.‖
• Scientists use it to indicate that the
stimulus was not consciously detected in a
given presentation.
• Because the only way to know if a stimulus
has been detected is to ask, it is very
difficult to interpret the results of research
on subliminal stimuli.

11. Perception of Minimal Stimuli
• What subliminal perception cannot
do
• Claims that subliminal stimuli in
advertisements can make people buy
things are unsupportable.
• This claim has been tested repeatedly
and no evidence has been found.
• Advertisements in American culture
have little need of subliminal stimuli.
They are overtly and effectively
manipulative.

12. Perception of Minimal Stimuli
• What subliminal perception cannot do
• Messages in music (recorded backwards
or superimposed) cannot make people do
anything, evil or otherwise.
• This claim has also been repeatedly tested
under controlled conditions.
• No one listening to the messages can discern
these messages.
• No one‘s behavior has been changed after
listening to music containing messages.

13. Perception of Minimal Stimuli
• What subliminal perception cannot do
• Subliminal audiotapes just don‘t work
• Claims that addictions can be overcome, self-
esteem can be improved, and general self-
improvement can be achieved through the use
of subliminal audiotapes are also unsupported.
• Any results achieved through the use of these
tapes can be attributed to the placebo effect or
to the individual user‘s motivation to improve.

14. Perception of Minimal Stimuli
• What subliminal perception can do
• Some subtle effects on subsequent
perception and emotion have been
supported
• ―Priming‖ individuals to see an object in
subsequent presentations has been achieved
through repeated presentations (Bar &
Biederman, 1998)
• Emotional states can be influenced by
subliminal presentation of messages that may
be perceived as emotionally loaded (Masling et
al., 1991)

15. Perception of Minimal Stimuli
• Subliminal perception
• The fact that subliminal perception can
influence behavior at all is interesting.
• But the effects overall are much smaller
than people hope or fear.

16. 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.

17. Somesthetic Senses
• Somesthetic senses - the body senses
consisting of the skin senses, the kinesthetic
sense, and the vestibular senses.
• ―Soma‖ – body
• ―Esthetic‖ - feeling
1. Skin senses - the sensations of touch,
pressure, temperature, and pain.
• Sensory receptors in the skin
• Gate-control theory - pain signals must pass through a
―gate‖ located in the spinal cord.

21. Somesthetic Senses
2. Kinestheticsense - sense of the location
of body parts in relation to the ground
and each other.
• Proprioceptive receptors (proprioceptors)
3. Vestibular senses - the sensations of
movement, balance, and body position.
Tells us where our body is oriented in
space.

22. Vestibular Sense
• Tells us where our
body is oriented in
space.
• Our sense of
balance.
• Located in our
semicircular canals
in our ears.

23. Kinesthetic Sense
• Tells us where our
body parts are.
• Receptors located
in our muscles and
joints.

25. Perception and Constancies
• Perception - the method by which
the sensations experienced at any
given moment are interpreted and
organized in some meaningful
fashion.
• Mental interpretation of sensation
results in perception

26. Perception and Constancies
PERCEPTION = SENSATION +
MEANINGFUL
INTERPRETATION
Ex: Smell we experience due to the
burning of an object is sensation and
understanding that the burning object is
rubber is PERCEPTION

27. Sensation and Perception
Sensation: your window to the world
Perception: interpreting what comes
in your window.

28. Perception and Constancies
• Size constancy - the tendency to interpret an
object as always being the same actual size,
regardless of its distance.
• Shape constancy - the tendency to interpret
the shape of an object as being constant,
even when its shape changes on the retina.
• Brightness constancy – the tendency to
perceive the apparent brightness of an object
as the same even when the light conditions
change.

30. Shape constancy

31. Gestalt Principles
• Figure–ground - the tendency to
perceive objects, or figures, as
existing on a background.
• Reversible figures - visual illusions
in which the figure and ground can
be reversed.

34. Do you see
an old lady
or a young
lady?

35. Do you see a
rabbit or a
duck?

36. The white and black stripes on
these zebras can be reversed –
both can serve as either figure or
ground.

37. Some Laws of Perceptual Organization
Gestalt Principles
• Closure - the tendency to
complete figures that are
incomplete.
Ex : While proof reading missing
letters escape from our attention &
our minds fill up the gap !

38. Laws of Perceptual Organization
Gestalt Principles
• Continuity - the tendency to
perceive things as simply as
possible with a continuous pattern
rather than with a complex, broken-
up pattern.( Organization of
perception appears to be going
infinitely in the same direction)
Ex : Cinema scenes though not individually, when
they run in a sequence at the rate of 15 frames per
second, they appear to be one and continuous

39. Laws of Perceptual Organization
Gestalt Principles
• Pragnanz – Pragnanz means compact but
significant. In perceiving we do not add the
different sensations received and edit them
so as to get at the meaningful interpretation
of the object perceived. We always perceive
anything as a whole configuration or pattern
so that it is simple, meaningful and stable.
Ex: On seeing a man riding a cycle, we do not
perceive the cycle and the rider separately, it appears
as a whole unit to us. The mental act of ‗organizing‘
takes place during perception
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40. Laws of Perceptual Organization
• Similarity - the tendency to perceive
things that look similar to each
other as being part of the same
group.
• Proximity - the tendency to
perceive objects that are close to
each other as part of the same
grouping. Menu

41. Menu

42. Depth Perception
• Depth perception - the ability to
perceive the world in three dimensions.
• Studies of depth perception
• Visual cliff experiment
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43. Perceptual Illusions
• Illusions are wrong / mistaken
perceptions
• Our perceptions are not always
true and accurate. Sometimes
errors do creep in our
perception when our mind
wrongly interpret the sensory
input, which is otherwise known
as ILLUSION

44. Perceptual Illusions
• Illusion of movement : Ex: A spot of
light in dark appears to be moving
around
• Illusion of perceptive : Ex: Two
parallel lines appears to meet at
along distance

45. Perceptual Illusions
• Müller-Lyer illusion - illusion of line length that
is distorted by inward-turning or outward-
turning corners on the ends of the lines,
causing lines of equal length to appear to be
different.
• Moon illusion – the moon on the horizon
appears to be larger than the moon in the
sky.
• Apparent distance hypothesis

49. Factors that Influence Perception
• Perceptual set (perceptual expectancy) - the
tendency to perceive things a certain way
because previous experiences or
expectations influence those perceptions.
• Top-down processing - the use of preexisting
knowledge to organize individual features into
a unified whole.
• Bottom-up processing - the analysis of the
smaller features to build up to a complete
perception.

52. Applying Psychology
• Extrasensory Perception (ESP) - claim of
perception that occurs without the use of
normal sensory channels such as sight,
hearing, touch, taste, or smell.
• Telepathy - claimed ability to read another person‘s thoughts, or
mind reading.
• Clairvoyance - supposed ability to ―see‖ things that are not actually
present.
• Precognition - supposed ability to know something in advance of its
occurrence or to predict a future event.
• Parapsychology - the study of ESP, ghosts,
and other subjects that do not normally fall
into the realm of ordinary psychology.

55. The Doorway to Psychology
You cannot know anything except through
the senses –
Anaxagoras
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