12. Visual Imagery€¦ · 12-04-2017 · Verbal Processes Non-Verbal Processes representational...
Transcript of 12. Visual Imagery€¦ · 12-04-2017 · Verbal Processes Non-Verbal Processes representational...
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Visual Imagery
Imagery
� Forming a picture in the mind without sensory input
� Mental imagery
� Visual imagery
� Paivio, Smyth and Yuille (1968)
� Subject studied word-pairs with each member varying in imagery
� High-High (H-H)
� High-Low (H-L)
� Low-High (L-H)
� Low-Low (L-L)
� Concrete words were
remembered better than
abstract words 0
2
4
6
8
10
12
14
H-H H-L L-H L-L
Mean
No
. R
ecalled
Imagery
� Dual Coding Theory (Pavio, 1971)
Sensory Systems
Logogens (lexical entries)
Images
Verbal Processes Non-Verbal Processes
representational connections
referentialconnections
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Imagery
� Are visual images different from verbal codes?
� Kosslyn (1975)
� Sentence verification task [A 1 has 2 . ]
� Semantic association between 1 and 2 varied
� A mouse has a back.
� A mouse has whisker.
� Subject told to form 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
� Kosslyn (1973)
� Mental scanning task
� Focus on part of a mental image (or real picture)
� Locate another part of the object
Scanning Mental Images
� Shepard and Metzler (1971)
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Imagery Debate
� Do mental images exist?
� Can we actually scan them, like a real picture?
� Tacit knowledge explanation
� Subjects may behave how they think that they should
� Subjects unconsciously use knowledge of spatial relations
� Zenon Pylyshyn
� Are visual images supported by spatial relationships or propositional relationships?
� Propositional relationships – images can be represented by abstract symbols
Imagery Debate
Spatial (depictive) Representation
Propositional Representation
“Sarah Palinis on top ofthe dinosaur.”
Imagery Debate
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Imagery Debate
� Propositional theory (Pylyshyn, 1973)
� Mental images are stored as propositions between parts
� “All knowledge, including spatial knowledge and memory for images, can be expressed in semantically-based propositions.”
� Explains mental scanning results of Kosslyn (1973)
PROPELLER HANDLE
MOTOR
REAR DECK CABIN
WINSHIELD PORTHOLE ANCHOR
FRONT DECK(behind) (behind)
(front of)(bottom of)
(rear of) (attached to)(side of)(top front of)
*each link-node is a propositional relationship
Spatial Relations in Mental Images
� To show evidence for spatial relations
� Performance (RTs) must vary as a function of distance
� Distances cannot be confounded with propositional links
� Kosslyn, Ball and Reiser (1978)
� Subjects encode a map into memory
� Scan between two points
� Spatial relationships prediction?
� Propositional theory prediction?
Spatial Relations in Mental Images
� Kosslyn, Ball and Reiser (1978)
� Scanning time linearly related to the distance between points
� Evidence favors spatial relations
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Spatial Relations in Mental Images
� Kosslyn (1975)
� Does size of mental image influence judgments of features?
� Imagine animals side-by side and answer questions about one
� Spatial relationships prediction?
� Propositional theory prediction?
Spatial Relations in Mental Images
� Kosslyn (1975) Results
� RTs were influenced by size of objects in the mental visual field
� Features more distinct
Spatial Relations in Mental Images
� Finke and Pinker (1982)
� Participants judged whether arrow pointed to dots that were previously seen
� Not instructed to use visual imagery
� No time to memorize, no tacit knowledge
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Spatial Relations in Mental Images
� Neural Evidence?
� LeBihan et al. (1993) - Perception and imagery activate visual cortex
� Increased cerebral blood flow in visual cortex when mentally scanning
Spatial Relations in Mental Images
� Galis et al. (2004)
� Spatial judgments about physical pictures or imagined pictures
� Measured BOLD signals in an fMRI
How Accurate are Mental Images?
� Relational information is distorted in mental maps
� Stevens & Coupe (1978)
� 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?
� Tversky (1981)
� Subjects drew map of the
western hemisphere, with certain
cities
Santiago
Miami