Perception
The process of organizing and interpreting
information, enabling us to recognize
meaningful objects and events.
Auditory Illusions
If the sounds do not work click here for link.
Absolute Threshold
• The smallest amount
of a stimuli we can
detect about half of
the time.
Subliminal Messages
Do you hear
"Now he
uses
marijuana.“?
Do you hear
“Ah, see me.
I'm not too
young”?
• Stimuli below our
absolute threshold.
• Backmasking
• 25th frame
• Do Subliminal
Messages work?
• Probably a placebo
effect
Do you hear Pass the
Do you
backwards.
Hear
gunhear"Play
now. It kills
the
words
sung.“?
love,
the love is cold”?
(Just Notable Difference)
Difference Threshold
The smallest amount of change needed to detect in a stimulus before we detect a
change.
Weber’s Law
• Computes the Just
Noticeable Difference.
• The change needed is
proportional to the
original intensity of the
stimulus.
• The more intense the
stimulus the more
change is needed to
notice the difference.
• 8% for vision.
Perceptual Ideas
Signal Detection theory
• Absolute thresholds
are not really
absolute.
• Things like motivation
or physical state can
effect what we
sense.
• False Positives
• False Negatives
My wife could sleep through a war, but if
one of our sons even whimpers, she is up!!!
Top-Down Processing
• We perceive by filling
the gaps in what we
sense.
• I _ant ch_co_ate ic_
cr_am.
• Based on our
experiences and
schemas.
• If you see many old men
in glasses, you are more
apt to process a picture
of an old man (even when
you may be in error).
Bottom-Up Processing
• Also called feature
analysis.
• We use the features
on the object itself
to build a
perception.
• Takes longer that
top-down but is more
accurate.
Click to see an example
of bottom –up
processing.
Figure Ground Relationship
Our first perceptual
decision is what is the
image is the figure and
what is the background.
Gestalt Psychology
• Gestalt psychologists focused on
how we GROUP objects together.
• We innately look at things in groups
and not as isolated elements.
• Proximity (group objects that are
close together as being part of
same group)
• Similarity (objects similar in
appearance are perceived as being
part of same group)
• Continuity (objects that form a
continuous form are perceived as
same group)
• Closure (like top-down
processing…we fill gaps in if we can
recognize it)
Constancy
• Objects change in
our eyes constantly
as we or they
move….but we are
able to maintain
content perception
• Shape Constancy
• Size Constancy
• Brightness
Constancy
Perceived Motion
• Stroboscopic effect
(flip book effect)
• Phi phenomenon
• Autokinetic Effect
(if people stare at a
white spotlight in a
dark room, it
appears to move.)
Depth Cues
• Eleanor Gibson and her
Visual Cliff Experiment.
• If you are old enough to
crawl, you are old enough
to see depth perception.
• We see depth by using
two cues that researchers
have put in two
categories:
• Monocular Cues
• Binocular Cues
Monocular Cues
• You really only need
one eye to use these
(used in art classes to
show depth).
• Linear Perspective
• Interposition
• Relative size
• Texture gradient
• Shadowing
Binocular Cues
• We need both of our
eyes to use these cues.
• Retinal Disparity (as an
object comes closer to
us, the differences in
images between our
eyes becomes greater.
• Convergence (as an
object comes closer our
eyes have to come
together to keep
focused on the object).