Visual ImagerySolving problems through imageryStudy of ImageryHow are mental images represented?Analog Images vs. PropositionsSome Questions about Mental ImagesImagery = perception in reverse?Imagery in Neural NetworksImagery & PerceptionJust as in visual images, level of detail in mental images can varyFinke and Kosslyn (1980) experimentFields of resolution are similar in perception and imageryVisual Imagery and Hemispatial NeglectEvidence from brain imaging (fMRI) for involvement of visual processing areas during visual imageryMental RotationExample TrialsResultsAre visual images also subject to visual illusions? Ponzo IllusionDifferences between pictures and mental imagesImagery and Ambiguous FiguresSlide 21Mental Images might miss important aspects of object being imaginedImagine this objectMental distortions in Cognitive MapsSlide 25Slide 26Slide 27Slide 28Cognitive maps are affected by conceptual knowledgeExperimental evidence for hierarchical organization in cognitive mapsSummaryExample Question (1)Example Question (2)Example Question (3)Visual ImagerySolving problems through imagery•What shape are mickey mouse’s ears?•How many windows are there in your apartment?•Which is a darker red – a cherry or an apple?•What is the shortest path from RH104 to Phoenix Grill?Study of Imagery•Banned by behaviorists•Possible subject of study in cognitive psychology–Cognitive psychology is distinguished from the earlier behaviorism by its claim that there are internal representations of knowledge on which the mind operates•However, this is a difficult area of study•Mental images are subjective•How can we show that images are used?•How are they represented?Stephen Kosslyn(did much of the research on mental imagery)How are mental images represented?•The analog vs. propositional debate–analog: the representation has the same structure as the thing represented –propositional: a sentence-like description of the image, non-spatial•Most studies mentioned seem to argue for analog representations (e.g., mental rotation, brain imaging studies). Yet mental images are not processed exactly the same as visual imagesAnalog Images vs. PropositionsAnalogImagine: The can is on the box. The can is blackPropositionson( can, box )black( can )Some Questions about Mental Images•What is the relationship between imagery and perception?•How are mental images processed and transformed?Imagery = perception in reverse?Imagery in Neural Networks•Mental images in neural networks can be produced by running the network “in reverse” -- activate class nodes (e.g. digit “3”) and running activation downwards to the input nodesinput hidden nodes output (e.g. digit class)Imagery & Perception •If the mechanisms used to perceive stimuli are also used to generate mental images, then we should predict: –Mental images should be quasy pictorial–Mental images should activate some of the brain areas involved with visual processingJust as in visual images, level of detail in mental images can varyDoes a rabbit have eyebrows?Imagine a bee next to a rabbit Imagine a elephant standing next to a rabbitDoes a rabbit have eyebrows?Finke and Kosslyn (1980) experimentfixationdot separationAngle of separationExperiment measures field of resolution: the angle of separation into the visual periphery where you cannot distinguish dots any longerFields of resolution are similar in perception and imageryHorizontal and vertical fields of resolution in perception and imagery as a function of dot separation and vividness of imagery. Data from Finke and Kosslyn (1980).Visual Imagery and Hemispatial Neglect(Bisiach and Luzzatti, 1978)Mental images from opposite sides of an imagined public landmarkEvidence from brain imaging (fMRI) for involvement of visual processing areas during visual imagery(Le Bihan et al., 1993)Mental Rotation•Can mental images be transformed in a way analagous to physical objects? How could we tell?•Mental rotation task: look at the time it takes to rotate two shapes into correspondence•Demo experiment:http://bjornson.inhb.de/?p=55Example Trialssamedifferentdifferentdifferentsamedifferentsame differentResults•linear relationship between angle of rotation and reaction time in object comparison•The mental process seems to be analogous to the physical process of rotation.Are visual images also subject to visual illusions? Ponzo IllusionWhich horizontal line is longer?Imagine an inverted “V” over these lines.Which horizontal line is longer?Differences between pictures and mental images•Mental images are more difficult to be reinterpreted–Mental image = perception + interpretation•Strong influence of conceptual knowledge on imagery–Simplification of object models –Distortions in cognitive mapsImagery and Ambiguous FiguresWhat would this object look like when rotated 90 degrees?Imagery and Ambiguous Figures•If you see one interpretation, it is very difficult to then imagine the other interpretation (unless you are trained in this task)•One difference between imagery and visual perception: visual images, unlike mental images, can be easily reinterpretedMental Images might miss important aspects of object being imagined•Imagine you have a cube between your thumb and index finger. One corner of the cube touches your thumb, and the diagonally opposite corner touches your index finger. Now, point to the locations of the rest of the corners in space.Many people point (incorrectly) to four points on the same plane half way between the top and bottom corners.Correct Solution:Imagine this objectDoes this figure contain a parallelogram?a) nob) yesc) not sured) what is a parallelogram??Mental distortions in Cognitive MapsWhich is further west? a) atlantic entrance to the panama canalb) pacific entrance to the panama canalWhich is further east? a)Floridab)ChileWhich is further south: a)Philadelphiab)RomeWhich is further east? a) Renob) San DiegoCognitive maps are affected by conceptual knowledge•Relative locations of small regions is determined by a conceptualization of larger regions.•Line of reasoning:•Nevada is east of California•Reno is in Nevada, San Diego in California,•Therefore, Reno must be east of San DiegoExperimental evidence for hierarchical organization in cognitive maps•Ss. study maps. Later, from memory, they judge relative position of locations x and y •Performance was better when superordinate information was congruent with