PerceptionPerceptionChapter 6Chapter 6
Perceptual Organization Form Perception Motion Perception Perceptual Constancy
Perceptual Interpretation Sensory Deprivation and
Restored Vision Perceptual Adaptation Perceptual Set Perception and Human Factor
The process of selecting, organizing, andinterpreting sensory information, which enables us
to recognize meaningful objects and events.
Selective AttentionPerceptions about objects change from moment to
moment. We can perceive different forms of theNecker cube; however, we can only pay attention
to one aspect of the object at a time.
Example: Cocktail Party Effect
Inattentional blindness refers to the inabilityto see an object or a person in our midst.
Simmons & Chabris (1999) showed that halfof the observers failed to see the gorilla-suited assistant in a ball passing game.
Change blindness is a form of inattentionalblindness in which two-thirds of individuals
giving directions failed to notice a change in theindividual asking for directions.
1998 Psychonomic Society Inc. Image provided courtesy of Daniel J. Simmons.
Change Blindness Video
Illusions provide good examples inunderstanding how perception is organized.Studying faulty perception is as important as
studying other perceptual phenomena.
Which line is longer?
In this picture, thevertical dimensionof the arch lookslonger than the
However, both areequal.
Rick Friedman/ Black Star
Illusion of a Worm
The figure on the right gives the illusion of a blue hazyworm when it is nothing else but blue lines identical
to the figure on the left.
1981, by perm
ission of Christoph R
edies and Lothar Spillm
ann and Pion Limited, London
It takes a great deal of effort to perceive this figure intwo dimensions.
ith kind permission of Elsevier Science-N
L. Adapted from
. & R
ichards, W. Parts of recognition. C
ognition, 63, 29-78
Organization of the visual field into objects(figures) that stand out from their surroundings
Time Savings Suggestion,
2003 Roger Sheperd.
When vision competes with our othersenses, vision usually wins a phenomena
called visual capture.
Visual Capture Examplee.g., movie projector voices (vision overtakes hearing)
This can be true with other senses as welle.g., finger touch and various tones; feeling like were moving when
simply watching an action movie18
Sensory and Perception BlendHow do we form meaningful perceptions from
We organize it!Gestalt psychologists showed that a figure formed
a whole different than its surroundings.
Our brains do a heck of a lot more than just merelyregister information about the world!
Gestalt Psychologists: Grouping
After distinguishing the figure from the ground,our perception needs to organize the figure into
a meaningful form using grouping rules.
Grouping & Reality
Although grouping principles usually help us constructreality, they may occasionally lead us astray.
Both photos by W
alter Wick. R
eprinted from G
agazine. . 1983 PC
es Limited Partnership
Naturally we look forpatterns in life
In addition to visualpatterns, we alsoconcoct patterns withour other senses
e.g., We tend to hear clocks gotick TICK tick TICK, but inreality, the sounds are thesame-tick tick tick tick,
Depth perception enables us to judge distances.Gibson and Walk (1960) suggested that human
infants (crawling age) have depth perception. Evennewborn animals show depth perception.
Binocular Cues:Need the use of two eyes
Retinal disparity: Images from the two eyes differ. Trylooking at your two index fingers when pointing them
towards each other half an inch apart and about 5 inchesdirectly in front of your eyes. You will see a finger
sausage as shown in the inset.
Convergence: Neuromuscular cues. When two eyes moveinward (towards the nose) to see near objects and outward
(away from the nose) to see faraway objects.*Two eyes are better than one!
Monocular Cues:Can use eyes together or either eye alone
Relative Size: If two objects are similar in size, weperceive the one that casts a smaller retinal image
to be farther away.
Interposition: Objects that occlude (block) otherobjects tend to be perceived as closer.
agritte, The Blank Signature, oil on canvas, N
ational Gallery of A
rt, Washington. C
ollection of M
r. and Mrs. Paul M
ellon. Photo by Richard C
Relative Clarity: Because light from distant objectspasses through more light than closer objects, we
perceive hazy objects to be farther away thanthose objects that appear sharp and clear.
Texture Gradient: Indistinct (fine) texture signalsan increasing distance.
Eric Lessing/ A
rt Resource, N
Relative Height: We perceive objects that are higher in ourfield of vision to be farther away than those that are lower.
Image courtesy of Shaun P. V
ecera, Ph. D.,
adapted from stim
uli that appered in Vecrera et al., 2002
Relative motion: Objects closer to a fixation point movefaster and in opposing direction to those objects that are
farther away from a fixation point, moving slower and inthe same direction. This is how we compute objects
Linear Perspective: Parallel lines, such as railroadtracks, appear to converge in the distance. The
more the lines converge, the greater theirperceived distance.
orker Collection, 2002, Jack Ziegler from
ll rights reserved.
Light and Shadow: Nearby objects reflect more light intoour eyes than more distant objects. Given two identical
objects, the dimmer one appears to be farther away.
From Perceiving Shape From
Shading by Vilayaur
achandran. 1988 by Scientific A
All rights reserved.
Motion PerceptionMotion Perception: Objects traveling towards usgrow in size and those moving away shrink in
size. The same is true when the observer moves toor from an object.
Phi Phenomenon: When lights flash at a certainspeed they tend to present illusions of motion.Neon signs use this principle to create motion
Two lights flashing one after the other.One light jumping from one point to another: Illusion of motion.
Perceiving objects as unchanging even asillumination and retinal images change. Perceptualconstancies include constancies of shape and size.
Shape Constancy 36
Stable size perception amid changing size of thestimuli.
The distant monster (below, left) and the top redbar (below, right) appear bigger because of
From Shepard, 1990
hoisnet/ The Image B
Both girls in the room are of similar height.However, we perceive them to be of differentheights as they stand in the two corners of the
Both photos from S. Schwartzenberg/ The Exploratorium
The Ames room is designed to demonstrate the size-distance illusion.
The color and brightness of square A and B are the same.Co
Perceiving familiar objects as having consistentcolor even when changing illumination filters
the light reflected by the object.
Color Constancy 42
Visual Illusions Video
Immanuel Kant (1724-1804) maintained thatknowledge comes from our inborn ways of
organizing sensory experiences.
John Locke (1632-1704) argued that we learn toperceive the world through our experiences.
How important is experience in shaping ourperceptual interpretation?
e.g., Amadou Diallo and police incident
What happens when we have sensationwithout perception?
After cataract surgery,blind adults were ableto regain sight. These
individuals coulddifferentiate figure andground relationships,yet they had difficultydistinguishing a circle
and a triangle(Von Senden, 1932).