Visual ImageryStudy of ImageryHow are mental images represented?Images vs. PropositionsSome Questions about Mental ImagesImagery = perception in reverse?Imagery & PerceptionJust as in visual images, level of detail in mental images can varyVisual Imagery and Hemispatial NeglectFinke and Kosslyn (1980) experimentFields of resolution are similar in perception and imageryEvidence from brain imaging (fMRI) for involvement of visual processing areas during visual imageryMental RotationExample TrialsResultsMental rotation in monkeysAre visual images also subject to visual illusions? Ponzo IllusionDifferences between pictures and imagesImagery and Ambiguous FiguresImagery and Ambiguous FiguresMental Images might miss important aspects of object being imaginedMental distortions in Cognitive MapsCognitive maps are affected by conceptual knowledgeExperimental evidence for hierarchical organization in cognitive mapsSummaryVisual ImageryStudy 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?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 imagesImages vs. PropositionsImagine: The can is on the box. The can is blackAnalog Propositionson( 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 & 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 varyImagine a elephant standingnext to a rabbitDoes a rabbit have eyebrows?Does a rabbit have eyebrows?Imagine a bee next to a rabbitShrinking mental images with brain damageBefore surgeryAfter surgeryVisual Imagery and Hemispatial NeglectMental images from opposite sides of an imagined public landmark(Bisiach and Luzzatti, 1978)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).Evidence 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://www.uwm.edu/~johnchay/mrp.htmExample Trialssamedifferentdifferentsamedifferentdifferent differentdifferentResults• linear relationship between rotation and reaction time in object comparison• The mental process seems to be analogousto the physical process of rotation.Mental rotation in monkeysStimulus: light comes onDirection indicated by motor cortexMMovement: to light 90o CCW SMSTime (10 msec intervals)Georgopoulos et al. (1989). Science, 243 (4888)., 234-236.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 images• Images cannot be reinterpreted– Images = 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:Mental distortions in Cognitive Maps• Which is further west: the atlantic or the pacific entrance to the panama canal?Which is further south: Philadelphia or Rome?Which is further east: Florida or Chile?Which is further east: Reno or San Diego?Cognitive 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 questionCongruentIncongruent(Stevens and Coupe, 1978)Summary• Imagined information is processed in similar ways to perceptual information– Neuroscience evidence (fMRI)– Neuropsychological evidence– Behavioral evidence:• Kosslyn studies/ Scanning studies• Mental rotation• Some visual illusions• But there are also differences:– Images are difficult to reinterpret– Cognitive distortions in mental