Visual Imagery
Imagery
Forming a picture in the mind without sensory input
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Mental imagery
Visual imagery
Paivio, Smyth and Yuille (1968)
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Subject studied word-pairs with each member varying in imagery
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High-High (H-H)
High-Low (H-L)
Low-High (L-H)
Low-Low (L-L)
Concrete words were
remembered better than
abstract words
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14
12
Mean No. Recalled
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10
8
6
4
2
0
H-H
H-L
L-H
L-L
Imagery
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Dual Coding Theory (Pavio, 1971)
Sensory Systems
representational
connections
Logogens (lexical
entries)
Images
referential
connections
Verbal Processes
Non-Verbal Processes
Imagery
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Are visual images different from verbal codes?
Kosslyn (1975)
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Sentence verification task [A 1 has 2 . ]
Semantic association between 1 and 2 varied
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A mouse has a back.
A mouse has whisker.
Subject told to for mental image of object or not
Condition
Example
No Imagery
Imagery
Low Association
A mouse has a back.
897 ms
1480 ms
Strong Association
A mouse has whisker.
825 ms
1605 ms
+72 ms
-125 ms
Scanning Mental Images
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Kosslyn (1973)
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Mental scanning task
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Focus on part of a mental image (or real picture)
Locate another part of the object
Scanning Mental Images
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Shepard and Metzler (1971)
Imagery Debate
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Do mental images exist?
Can we actually scan them, like a real picture?
Tacit knowledge explanation
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Subjects may behave how they think that they should
Subjects unconsciously use knowledge of spatial relations
Zenon Pylyshyn
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Are visual images supported by spatial relationships or
propositional relationships?
Spatial, or depictive, relationships
Propositional relationships
Imagery Debate
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Propositional theory (Pylyshyn, 1973)
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Mental images are stored as propositions between parts
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“All knowledge, including spatial knowledge and memory for images, can be
expressed in semantically-based propositions.”
Explains mental scanning results of Kosslyn (1973)
REAR DECK
(rear of)
(behind)
CABIN
(behind)
FRONT DECK
(top front of)
(side of)
(attached to)
WINSHIELD
PORTHOLE
ANCHOR
MOTOR
(bottom of)
PROPELLER
(front of)
HANDLE
*each link-node is a
propositional relationship
Imagery Debate
Spatial (depictive )
Representation
Propositional
Representation
“Sarah Palin
is on top of
the dinosaur.”
Evidence for Spatial Relations in Mental
Images
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To show evidence for spatial relations
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Performance (RTs) must vary as a function of distance
Distances cannot be confounded with propositional links
Kosslyn, Ball and Reiser (1978)
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Subjects encode a map into memory
Scan between two points
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Spatial relationships prediction?
Propositional theory prediction?
Evidence for Spatial Relations in Mental
Images
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Kosslyn, Ball and Reiser (1978)
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Scanning time linearly related to the distance between points
Evidence favors spatial relations
Evidence for Spatial Relations in Mental
Images
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Kosslyn (1975)
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Does size of mental image influence judgments of features?
Imagine animals side-by side and answer questions about one
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Spatial relationships prediction?
Propositional theory prediction?
Evidence for Spatial Relations in Mental
Images
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Kosslyn (1975) Results
RTs were influenced
by size of objects in the
‘mental visual field’
 Features more distinct
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Evidence for Spatial Relations in Mental
Images
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Neural Evidence?
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LeBihan et al. (1993)
Perception and imagery
activate visual cortex
 Increased cerebral blood flow
in visual cortex when mentally
scanning
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Evidence for Spatial Relations in Mental
Images
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Galis et al. (2004)
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Spatial judgments about physical pictures or imagined pictures
Measured BOLD signals in an fMRI
How Accurate are Mental Images?
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Relational information is distorted in mental maps
Stevens & Coupe (1978)
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Asked subjects about where one geographical location was
with respect to another
Example: Is San Diego east
or west of Reno, Nevada?
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How Accurate are Mental Images?
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Tversky (1981)
Subjects drew map of the
western hemisphere, with certain
cities
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Miami
Santiago