Mental Imagery
Analog Code
(depiction): representation has characteristics of physical object (spatial)
Propositional Code
(description): representation is abstract, language-like
Parallels in Imagery and Perception
- checkerboard - eye movement patterns similar to when imagining and when viewing
Brain Damage: LH
- damaged temporo-occipital regions of temporal lobe - can't recognize objects, animals, wife, children - can copy objects but not identify
Brain Imagery during imagery tasks
- fMRI -TMS V1 important for both visual perception and mental imagery
Cognitive Map Conclusion
- spatial representations generally good (function in world) but... - not always accurate in details - systematic errors
Example of mental imagery
- which darker green: frozen pea or pine tree? - in which hand does Statue of Liberty hold torch? -will new futon fit in living room?
Cognitive Maps: Making Decisions
- which further west, San Diego or Reno?
Cognitive Map: Heuristics
1. alignment 2. rotation
Propositional Code Evidence
Conclusion: "Cannot set understanding aside to reinterpret the form because no representation of geometry standing free of specifications one has in mind"
Imagery Debate
General agreement that experience picture-like mental images, but what is underlying representation? DEBATE: depictive vs. descriptive
Addressing the Debate
Imagery and perception Does mental imagery embody spatial relationships (like perception)? Does it activate the same brain areas that are involved in perception?
Imagery and Distance
Linear relationship between distance and RT
Imagery Conclusion
Neuroimaging results: Kosslyn claims analog wins Both may be involved, but analog primary representation
Patients with trouble knowing location
Parallel effect in imagery: Describing relative locations in neighborhood; blindfold---> can't point to object locations
Patients with damage (stroke) may have object perception problems
Parallel effect in imagery: Reporting colors of common objects; drawing/describing faces, objects, animals
Nature of Mental Images
Reed - low % can remember that there was a parallelogram
Imagery and Perception
Segal and Fusella - imagery interfered with perception
Mental Rotation
Shepard and Metzler Results: further around rotated, longer to make decision
fMRI
V1 active during imagery
Big Questions
What is nature of mental "image" representation? Pictorial or not? What is relationship between imagery and perception?
Imagery in Blind People
When pointing to left and right sides: - All produce larger angles for larger objects - Sighted produce smaller angles as distance to object increased -- Blind did not - Spatial rather than visual imagery
Theories of Represntation
analog code and propositional code
Which class of researchers would be more likely to study imagery?
cognitive psychologists
Steven Kosslyn
depictive/analog
Zenon Pylyshyn
descriptive/propositional
Neuropsychological Evidence
different brain areas responsible for spatial and visual aspects of imagery
TMS
disrupting V1 causes problems with vision and visual imagery
Alignment Heuristic
geographic entities remembered as more lined up than are ex: Europe and US
Results of LH
impaired visual imagery, but intact spatial imagery
Early Work in studying imagery
introspection (Galton)
Size of Image
larger RT time when next to elephant vs. bee
Mental Imagery
mental representation of objects not currently present
Cognitive Map
mental representation of physical environment
See Systematic Distortions
more orderly and regular than real world
Rotation Heuristic
represent something that is slightly tilted as more vertical or more horizontal ex: California coastline
Roger Shepard
use of imagery - measure RT to judge aspects of mental images
LH Imagery Tasks
visual (color, animal, shapes) VS. spatial (rotations, mental scanning, relative locations of states)
Neurological Parallels in Imagery and Perception
visual neglect: shave 1/2 face and eat 1/2 plate of food
