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 thanabstract words

H-H H-L L-H L-L0

2

4

6

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Mea

n N

o. R

ecal

led

Imagery Dual Coding Theory (Pavio, 1971)

Sensory Systems

Logogens (lexical entries)

Images

Verbal Processes Non-Verbal Processes

representational connections

referentialconnections

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 for mental image of object or notCondition Example No

ImageryImagery

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)

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? Spatial, or depictive, relationships Propositional relationships

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

Imagery DebateSpatial (depictive ) Representation

Propositional Representation

“Sarah Palinis on top ofthe dinosaur.”

Evidence for 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?

Evidence for Spatial Relations in Mental Images Kosslyn, Ball and Reiser (1978)

Scanning time linearly related to the distance between points

Evidence favors spatial relations

Evidence for 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?

Evidence for Spatial Relations in Mental Images Kosslyn (1975) Results

RTs were influencedby size of objects in the ‘mental visual field’ Features more distinct

Evidence for Spatial Relations in Mental Images Neural Evidence?

LeBihan et al. (1993) Perception and imageryactivate visual cortex Increased cerebral blood flowin visual cortex when mentallyscanning

Evidence for 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 eastor west of Reno, Nevada?

How Accurate are Mental Images? Tversky (1981)

Subjects drew map of thewestern hemisphere, with certaincities

Santiago

Miami