S EEING AND V ISUALIZING: I T ’ S N OT W HAT Y OU T HINK * An Essay On Vision and Visual Imagination {CHAPTERS 6, 7, 8 FOR CLASS USE} ZENON PYLYSHYN, RUTGERS CENTER FOR COGNITIVE SCIENCE Table of Contents 6. Seeing With the Mind’s Eye 1: The Puzzle of Mental Imagery .................................................6-2 6.1 What is the puzzle about mental imagery?..............................................................................6-2 6.2 Content, form and substance of representations ......................................................................6-7 6.3 What is responsible for the pattern of results obtained in imagery studies?.................................6-9 6.3.1 Cognitive architecture or tacit knowledge .........................................................................................................6-9 6.3.2 Problem-solving by “mental simu lation”: Some additional examples ..........................................................6-13 6.3.2.1 Scanning mental images ............................................................................................................................6-14 6.3.2.2 The “size” of mental images......................................................................................................................6-18 6.3.2.3 Mental “paper folding”..............................................................................................................................6-19 6.3.2.4 Mental Rotation..........................................................................................................................................6-21 6.3.3 A note concerning cognitive penetrability and the appeal to tacit knowledge........................................6-23 6.3.4 Summary of some possible reasons for observed patterns of imagery findings .......................................6-25 6.4 Some alleged properties of images ......................................................................................6-27 6.4.1 Depiction and mandatory properties of representations...............................................................................6-27 6.5 Mental imagery and visual perception .................................................................................6-29 6.5.1 Interference between imaging and visual perception.....................................................................................6-31 6.5.2 Visual illusions induced by superimposing mental images ...........................................................................6-31 6.5.3 Imagined versus perceived motion ...................................................................................................................6-33 6.5.4 Extracting novel information from images: Visual (re)perception or inference? ........................................6-35 6.5.5 What about the experience of visualizing?.....................................................................................................6-38 7. Seeing With the Mind’s Eye 2: Searching for a Spatial Display in the Brain..............................7-1 7.1 Real and “functional” space................................................................................................7-1 7.2 Why do we think that images are spatial? ..............................................................................7-5 7.2.1 Physical properties of mental states: crossing levels of explanation.............................................................7-5 7.3 Inheritance of spatial properties of images from perceived space ..............................................7-8 7.3.1 Scanning when no surface is visible.................................................................................................................7-10 7.3.2 The exploitation of proprioceptive or motor space.........................................................................................7-11 7.4 The search for a real spatial display....................................................................................7-15 7.4.1 Aside: Does biological evidence have a privileged status in this argument?............................................7-15 7.4.2 The argument from differential activity in the brain .......................................................................................7-17 7.4.3 The argument from clinical cases of brain damage ........................................................................................7-20 7.5 What would it mean if all the neurophysiological claims turned out to be true?........................7-22 7.5.1 The ‘mind’s eye’ must be very different from a real eye ................................................................................7-23 7.5.2 The capacity for imagery is independent of the capacity for vision............................................................7-24 7.5.3 Images are not two-dimensional displays........................................................................................................7-24 7.5.4 Images are not retinotopic ..................................................................................................................................7-25 7.5.5 Images do not provide inputs to the visuomotor system..............................................................................7-26 * Manuscript of a forthcoming book from MIT Press. Please do not quote without permission. Ó 1998 by Zenon Pylyshyn 7.5.6 Examining a mental image is very different from perceiving a display.........................................................7-27 7.5.7 What has neuroscience evidence done for the “imagery debate”?.............................................................7-30 7.6 What, if anything, is special about mental imagery? .............................................................7-31 7.6.1 What I am not claiming: Some misconceptions about objections to the picture-theory ..........................7-31 7.6.2 What constraints should be met by a theory of mental imagery?................................................................7-33 8. Seeing With the Mind’s Eye 3: Visual Thinking .......................................................................8-1 8.1 Different “styles” of thinking...............................................................................................8-1 8.2 Form and content of thoughts: What we think with and what we think about.............................8-1 8.2.1 The illusion that we experience the form of our thoughts ...............................................................................8-1 8.2.2 Do we think in words?...........................................................................................................................................8-2 8.2.3 Do we think in pictures?.......................................................................................................................................8-4 8.2.4 What form must thoughts have?.........................................................................................................................8-6 8.3 How can visual displays help us to reason?............................................................................8-7 8.3.1 Diagrams as logical systems that exploit visual operations............................................................................8-7 8.3.2 Diagrams as guides for derivational milestones (lemmas).............................................................................8-10 8.3.3 Diagrams as a way of exploiting visual generalization...................................................................................8-11 8.3.4 Diagrams as ways of tracking instances and alternatives .............................................................................8-15 8.3.5 Diagrams as non-metric spatial models and spatial memory .........................................................................8-16 8.3.6 Diagrams drawn from memory can allow you to make explicit what you knew implicitly .........................8-17 8.4 Thinking with mental diagrams ..........................................................................................8-18 8.4.1 Using mental images............................................................................................................................................8-18 8.4.2 Using mental models ...........................................................................................................................................8-20 8.4.3 What happens during visualization?................................................................................................................8-21 8.5 Imagery and imagination...................................................................................................8-22 8.5.1 How does creativity connect with imagery?....................................................................................................8-25 8.5.1.1 Enhancing creative thinking .....................................................................................................................8-26 References ...................................................................................................................................8-28 6. SEEING WITH THE M IND’S EYE 1: T HE PUZZLE OF MENTAL IMAGERY 6.1 What is the puzzle about mental imagery? In earlier chapters I discussed various connections among the world, the visual system, and the central cognitive system that is responsible for reasoning, inference, decision-making and