Transcript Chapter 5 Perceiving the World

Chapter 5
Perceiving the World
Some Key Terms
• Perception: How we assemble sensations
into meaningful patterns
• Bottom-up processing: Analyzing information
starting at the bottom (small units) and going
upward to form a complete perception
• Top-down processing: Pre-existing
knowledge that is used to rapidly organize
features into a meaningful whole
Selective Attention
• Giving priority to a particular incoming message.
• Dividing Attention: Allotting mental space or effort to
various tasks or parts of a task
Perceptual Expectancies
• Perceptual expectancy (set): Past
experiences, motives, contexts, or
suggestions that prepare us to perceive in a
certain way
Attention and Perception
• Inattentional blindness: Failure to perceive
a stimulus that is in plain view, but not the
focus of attention
• Orientation response: Bodily changes that
prepare an organism to receive
information from a particular stimulus
Perceptual Grouping
• Figure–ground organization: Inborn; part of a
stimulus stands out as an object (figure)
against a plainer background (ground)
• Reversible gigure: Figure and ground that
can be reversed
A challenging example of perceptual organization. Once the camouflaged insect
(known as a giant walking stick) becomes visible, it is almost impossible to view the
picture again without seeing the insect.
Fig. 5-6, p. 156
Gestalt Principles of Organization
• Nearness: Stimuli that are near each other tend
to be grouped together
• Similarity: Stimuli that are similar in size, shape,
color, or form tend to be grouped together
• Continuation, or continuity: Perceptions tend
toward simplicity and continuity
Gestalt Principles of Organization (cont)
• Closure: Tendency to complete a figure so that it
has a consistent overall form
• Contiguity: Nearness in time and space;
perception that one thing has caused another
• Common region: Stimuli that are found within a
common area tend to be seen as a group
More on Perception
• Size constancy: Perceived size of an object
remains constant, despite changes in its retinal
image size
• Native perception: A perceptual experience
based on innate processes
Convergence
• For a simple illustration of convergence, have students
focus on a distant point and then bring a finger up into
the line of sight. The finger will appear “transparent”
because the line of sight is nearly parallel. If students
then look directly at the finger, it will once again become
“solid” (convergence). A variation on this (which also
illustrates retinal disparity and fusion) involves again
fixating on a distant point. This time the tips of the index
fingers of both hands should be brought together in the
line of sight, about twelve inches from the eyes. Students
should see a small “sausage” forming and disappearing
between their fingertips as the two retinal images
overlap.
(a) Linear perspective. (b) Relative size. (c) Light and
shadow. (d) Overlap. (e) Texture gradients. Drawings
in the top row show fairly “pure” examples of each of
the pictorial depth cues. In the bottom row, the
pictorial depth cues are used to assemble a more
realistic scene.
Fig. 5-15, p. 162
Some More Key Terms
• Empirical perception: A perception strongly
influenced by prior experience
• Shape constancy: The perceived shape of
an object is unaffected by changes in its
retinal image
• Brightness constancy: Apparent brightness
of an object stays the same under
changing lighting conditions
What do you see in this
painting?
This painting by abstract
artist Al Held is 9 feet by
9 feet. If you process the
painting “bottom-up,” all
you will see is two small
dark geometric shapes.
Would you like to try
some top-down
processing? Knowing the
painting’s title will allow
you to apply your
knowledge and see the
painting in an entirely
different way.
The title? It’s The Big N.
Can you see it now?
Fig. 5-1, p. 151
Depth Perception
• Definition: Ability to see three-dimensional
space and to accurately judge distances
• Visual cliff: Apparatus that looks like the
edge of an elevated platform or cliff on one
side and a tabletop on the other
Depth
• Depth cues: Features of the environment,
and messages from the body, that supply
information about distance and space
• Binocular depth cue: Depth cue that can be
sensed with two eyes
• Monocular depth cue: Depth cue that can be
sensed with one eye
Muscular Cues for Depth Perception
• Retinal disparity: Discrepancy in the images
that reach the right and left eyes
• Stereotopic vision: Three-dimensional sight;
perception of space and depth caused by the
fact that the eye receives different images
Relative Motion (Motion Parallax)
• Nearby objects move a lot as your head
moves; distant objects move slightly
• People are more likely to say trucks are
moving faster than cars because they
are bigger
On a dry lake bed, relative size is just about the only depth cue available for
judging the camera’s distance from this vintage aircraft. What do you
estimate the distance to be? For the answer, look ahead to
Fig. 5-16, p. 163
Fig. 5-21, p. 165
Some Illusions
• Moon illusion: Apparent change in size that
occurs as the moon moves from the horizon
(large moon) to overhead (small moon)
• Apparent-distance hypothesis: Horizon
seems more distant than the night sky
Fig. 5-8a, p. 156
Fig. 5-8b, p. 156
Fig. 5-29, p. 170
Fig. 5-20, p. 165
Perceptual Habits
• Ingrained patterns of organization and
attention
– Other-race effect: Tendency to be better at
recognizing faces from one’s own racial
group than faces from other racial or ethnic
groups
– Active movement: Self-generated action;
accelerates perceptual adaptation
– Korean Monks
Perceptual Comparisons
• 4 volunteers are going to guess my height and
weight
• They leave the classroom
• Two more volunteers stand on either side of me
for each person guessing
• Rest of class, write down their guesses
• Did the guesses change based on who was
around me?
Context
• Context: Information surrounding a stimulus;
affects perception
• Frames of reference: Internal standards for
judging stimuli
Fig. 5-24a, p. 166
Illusions: Is What You See What You Get?
• Illusion: Length, position, motion, curvature, or
direction is constantly misjudged
• Hallucination: When people perceive objects or
events that have no basis in external reality
• Stroboscopic movement: Illusory motion
perceived when objects are shown in rapidly
changing positions
Müller-Lyer Illusion
• Two equal-length lines tipped with inward or
outward pointing V’s appear to be of different
length; based on experience with edges and
corners of rooms and buildings
Extrasensory Perception (ESP)
• Purported ability to perceive events in ways
that cannot be explained by known capacities
of sensory organs
• Parapschology: Study of ESP and other psi
phenomena (events that seem to defy
accepted scientific laws)
Parapsychological “Abilities”
• Clairvoyance: Purported ability to perceive
events at a distance or through physical
barriers
• Telepathy: Purported ability to read minds
• Precognition: Purported ability to
accurately predict the future
• Psychokinesis (mind over matter):
Purported ability to influence inanimate
objects by willpower
More ESP Terms
• Zener cards: Deck of 25 cards, each having one
of five symbols
• Run of luck: Statistically unusual outcome that
could occur by chance alone (e.g., getting five
heads in a row, two jackpots within six pulls of a
slot machine)
• Throughout your lecture, I made a small but
novel gesture every few minutes. The gesture
should be something that would draw little
attention if done once. Did you become aware of
the gesture as it was repeated? Or were you
used to it? Discuss their perceptions near the
end of the session.
Stroop Effect
• Handouts