Top-Down versus Bottom-Up
Perception
•
Top-Down
– Perceive the whole and then individual parts as
needed.
– Experience-driven as opposed to stimulus or inputdata driven.
– Quick and highly inferential but also a source of
misperception.
•
Bottom-up
– Perceive the individual parts and organize them into a
whole, if possible.
– Information available in the stimulus itself.
Arranged by Dr. Gordon Vessels 2005
Bottom-Up Processing
Prior Knowledge, Experience,
etc.
Perception
Stimuli Processing
Stimuli Input
Created by Dr. Gordon Vessels 2005
David Marr’s Computational
Bottom-Up Approach
• Marr wanted to understand mechanisms
of vision rather than just behaviors
associated with it.
• …he wanted to link neurophysiology
with psychology.
• He took an information processing view
of the mind…
• …and aimed to describe perception in
terms of computations on sense data…
• …to extract high level visual experience.
Source: Bell, Vaughan (2004). Perception and perceptual distortion. A PPT presentation retrieved at
http://www.cardiff.ac.uk/psych/home/bellv1/ Used here with the author’s written permission. Slide arrangement by Vessels, 2005.
Marr’s Stages of Visual
Processing
• Marr proposed there were distinct stages
of processing in visual perception:
» Stage 1: Raw Primal Sketch
» Stage 2: Complete Primal Sketch
» Stage 3: 2½D Sketch
» Stage 4: Full 3D Representation
Source: Bell, Vaughan (2004). Perception and perceptual distortion. A PPT presentation retrieved at
http://www.cardiff.ac.uk/psych/home/bellv1/ Used here with the author’s written permission. Slide arrangement by Vessels, 2005.
Stage 1: Raw Primal Sketch
This involves the extraction of information
regarding edges and intensity changes.
Source: Bell, Vaughan (2004). Perception and perceptual distortion. A PPT presentation retrieved at
http://www.cardiff.ac.uk/psych/home/bellv1/ Used here with the author’s written permission. Slide arrangement by Vessels, 2005.
Stage 2: Complete Primal Sketch
• After the Raw Primal Sketch…
• Marr [proposed]… we create a
Complete Primal Sketch by grouping
surfaces and common areas.
• The Gestalt Psychologists of the early
19th Century demonstrated many
different ways in which we can group
objects.
Source: Bell, Vaughan (2004). Perception and perceptual distortion. A PPT presentation retrieved at
http://www.cardiff.ac.uk/psych/home/bellv1/ Used here with the author’s written permission. Slide arrangement by Vessels, 2005.
Stage 3: 2½D Sketch
• After gaining information about
groupings and surfaces, the viewer needs
some spatial information.
• Marr called this stage the 2½D Sketch to
emphasis that this stage does not give a
full 3D representation.
• Rather, just an estimate of the spatial
locations of objects and materials in
relation to the viewer.
Source: Bell, Vaughan (2004). Perception and perceptual distortion. A PPT presentation retrieved at
http://www.cardiff.ac.uk/psych/home/bellv1/ Used here with the author’s written permission. Slide arrangement by Vessels, 2005.
2½ D Sketch: Depth Cues
• We perceive much information
from which we infer depth:
» Binocular disparity
» Texture gradients
» Occlusion
» Convergence
» Relative Size
Source: Bell, Vaughan (2004). Perception and perceptual distortion. A PPT presentation retrieved at
http://www.cardiff.ac.uk/psych/home/bellv1/ Used here with the author’s written permission. Slide arrangement by Vessels, 2005.
Stage 4: 3D Representation
• The final stage of Marr’s theory.
• A full 3D description of our spatial
environment involving the
identification of the structure of
objects and materials in our visual
field.
• It allows us to work out the 3D
environment from a non-egocentric
point-of-view.
Source: Bell, Vaughan (2004). Perception and perceptual distortion. A PPT presentation retrieved at
http://www.cardiff.ac.uk/psych/home/bellv1/ Used here with the author’s written permission. Slide arrangement by Vessels, 2005.
Gregory on Top-Down Perception
• Gregory proposes that we use our prior
“experience of the world to shape how we
perceive” stimuli we encounter in it.
• His theory of perception is called Top-Down,
• Which means we use activated conceptual
schemas and memory networks (our stored
knowledge), more or less automatically and
subconsciously, to shape our perceptions or
to interpret our sensory input ― sometimes
correctly and sometimes not.
• He confirmed many of his theoretical
propositions using visual illusion research.
Primary source Bell, Vaughan (2004). Perceptions and perceptual distortions, a PPT show accessed at
http://www.cf.ac.uk/psych/home/bellv1/conf/VaughanPerceptionLecture2004.ppt#1. Written permission granted 5-5-05.
Top-Down Processing
Culture
Social Class
Personality
Temperament
Prior Stimuli
Perceived
Values
Beliefs
Prejudices
Attitudes
Occupation
Education
Immediate
Mental Set
Prior Knowledge,
Experience, etc.
Present Fatigue
Energy Level
Needs, Moods
Mental Health
Long-term Memory
Schemas
Specific Life
Experiences
Perception
Stimuli Processing
Stimuli Input
Created by Dr. Gordon Vessels 2005
Presence of
Authority
Knowledge
Vocabulary
If all of these people were at the same football game, who among them was most likely to
have perceived what actually happened on a controversial play where the receiver may
have fumbled the ball before his knees touched the ground? Whose perceptions were the
most bottom up? Whose perceptions were the most top-down and thus influenced and
quickened in terms of inference by their present needs, biases, and heightened emotion?
Whose perception may have been the most accurate and objective based on his or her
knowledge of the game? When the head referee reviewed the replays, did he use topdown or bottom-up perception primarily? What top-down influence may have made it
possible for his perceptions to have been highly accurate? Did these people literally see
something different? Do they really believe what they claimed to have seen?
What do you see? The
word liar in script or
cursive? A face looking
down? Those shown
artwork with faces were
more inclined than
others to see the word
liar.
What do you see? A face looking
down? The word Liar in script or
cursive? Those who first read stories
about deception were more inclined
than others to see the word Liar.
Arranged by Dr. Gordon Vessels 2004
Top-Down &
Bottom-Up Processing
Prior Knowledge, Experience,
etc.
Perception
Stimuli Processing
Stimuli Input
Created by Dr. Gordon Vessels 2005