Visual Imagery (Chapter 10 HC)
Is imagery just a "laboratory phenomenon" or does it occur in real life?
Occurs in real life: For example, the German chemist Kekule discovered how the structure of benzene would look by imaging the snake that loops in a circle eating its tail.
What is the visual categorization?
Dot pattern categorization task: - patients with MTL injury and amnesia perfom task implicitly but not explicitly - used visual cortex (implicit)
What is visual imagery?
Seeing in the absence of a visual stimulus
What is the reverse hierarchy theory?
Visual system viewed as a hierarchy of cell types and cortical areas - feedforward = implicit (from the corticial/cell to mental imagery) - feedback = explicit (starts at higher level) - explains categorization and attentional blindness
Describe how experiments using the following physiological techniques have provided evidence of parallels between imagery and perception: (a) brain imaging, (b) deactivation of part of the brain, (c) recording from single neurons
(a): 1. Activity in the striate cortex increased both when a person observed presentations of actual visual stimuli and when the person was imagining the stimulus. 2. When participants generated a question that involved imagery, the visual cortex generated a greater response. 3. fMRI activation showed the responses in areas of frontal lobe and middle showed that activation was the same with perception and imagery. However, the back of the brain (occipital lobe), there was a greater response in the perception condition. 4. When participants created images using visual imagery, some areas associated with nonvisual were deactivated (decreased activation). Possibly because mental images are more fragile than real perception. (b) TMS was applied to the visual area of the brain while participants did either a perception or imagery task. Results indicated that the stimulation caused participants to respond more slowly both for perception and imagery, providing evidence that the visual cortex plays a causal role in both perception and imager (c) imagery neurons: neurons respond to seeing on particular object (e.g. baseball,face) when a person perceives it and also when the person imagines it.
Describe the neuropsychology studies that provide evidence of parallels between imagery and perception.
1. Patient M.G.S - performed the mental walk task before and after having part of her right occipital lobe removed - before surgery, she imagined herself getting 15 ft near the horse, but after she said 35 ft. - removal of part of the visual cortex reduced the size of her field of view allowing the horse to fill up the field when she was farther away 2. Patient with unilateral neglect - damage to parietal causes person to ignore objects in half their visual field - patient neglected his left side of the mental image, just like how he neglected the left side of his perceptions 3. R.M - damage to occipital and parietal lobes - He was able to recognize and draw pictures of objects in perception, however, he failed to do so when asked to draw objects from memory (imagery). C.K - suffered from visual agnosia, inability to visually recognize objects - he couldn't recognize parts of objects and name pictures (perception), however, he was able to draw objects from memory in rich detail (imagery)
How have experiments demonstrated interactions between imagery and perception? What additional evidence is needed to help settle the imagery debate, according to Farah?
1. Perky experiment had participants imagine an image on the wall, however, the researcher displayed a very dim outline of the image. Results had participants match the images that were projected, and they also mistook the projected image and an actual mental image 2. Farah instructed participants to imagine either the letter H or T on the screen. After, they would press a button that would cause two squares to flash either H or T. Results showed that the target latter was detected more accurately when the participant had been imagining the same letter rather than a different letter. Despite the evidence, can't rule out propositional explanation. Farah proposed that we investigate how the brain responds to visual imagery instead of relying on behavior
What is mental imagery?
Ability to recreate the sensory world in the absence of physical stimuli, also occurs in senses other than vision
Describe the depiction v. description experiment involving child development
Children were easily able to imagine the spatial layout of a house if given a map. They were able to follow direction asked by the researcher. Children had more difficulty when they were described the layout especially when the rooms were diagonal instead of straight rows
List the important events in the history of the study of imagery in psychology, from the imageless thought debate of the 1800s to the studies of imagery that occurred early in the cognitive revolution in the 1960s.
Imageless thought debate: - Some psychologists believed that imagery is important for though and others debated that thinking can occur without images. - 1883 study observed that people who couldn't form visual images had no difficulty thinking - behaviorists branded the study of imagery and unproductive Cognitive revolution: - Conceptual peg hypothesis: concrete nouns (e.g. boat-hat) create images that other words can "hang onto". - e.g. presenting the pair boat-hat creates an image of a boat, then presenting the word boat later will bring back the boat image, and allows participants to remember the hat. - Mental rotation task: time it took decide if the two images were the same depended on how different the angle was. - participants were mentally moving one image to see if it matched the other - imagery and perception share the same mechanisms
Describe the spatial (or depictive) and propositional explanations of the mechanism underlying imagery. How can the propositional explanation interpret the results of Kosslyn's boat and island image-scanning experiments?
Imagery debate: debate about whether imagery is based on spatial mechanisms or if based on mechanisms related to language called propositional mechanisms (e.g. "cat is under the table") - Pylyshyn says that because we experience imagery as spatial doesn't mean that the underlying representation is spatial - epiphenomenon: something that accompanies the real mechanism but is not actually part of the mechanism - the propositional explanation would interpret results from Kossyln's research by showing how imagery operates in a way similar to semantic networks. That is, parts of the boat is connected with lines that indicate the distance.
How did Kosslyn use the technique of mental scanning (boat and island experiments) to demonstrate similarities between perception and imagery?
Kosslyn said that if imagery, like perception, is spatial, then it should take participants longer to find places that are far apart - Boat experiment: Participants were told to image a boat and then to focus on a initial point (e.g. anchor). Researcher asked them to locate the another point on the other side of the boat (e.g. motor). Results showed a slower reaction time because participants scanned across the image. - Island experiments: Participants asked to imagine an island that contained seven different locations and told to scan between pairs of locations. Results showed that participants reacted longer when scanning between longer distances which supports the idea that visual imagery is spatial.
Some of the neuropsychological results demonstrate parallels between imagery and perception, and some results do not. How has Behrmann explained these contradictory results? What are some differences between imagery and perception?
Mechanisms of perception and imagery overlap only partially, with the mechanisms for perception being located at both lower and higher centers and mechanisms for imagery being located mainly in higher visual centers Perception involves bottom up processing (i.e. light enters retina and so forth), and imagery involves top down processing (i.e. memory areas that don't depend on outside input) - for example, C.K. perception bad because damage early in the processing stream but his imagery is good because his higher level areas of the brain are intact
What are some differences between imagery and perception? What have most psychologists concluded about the connection between imagery and perception?
Most psychologists concluded that imagery and perception are closely related and share some (but not all) mechanisms Differences: - perception is automatic, but imagery needs to be generated with some effort - perception is stable and imagery is fragile - harder to manipulate mental images than images that are created perceptually as shown by Chalmers and Reisberg when they showed ambiguous figures (can you see a rabbit or a duck). Perceptually easy to flip images, but hard to do so if you are holding a mental image of the figure
Under what conditions does imagery improve memory? Describe techniques that use imagery as a tool to improve memory. What is the basic principle that underlies these techniques?
Placing images at locations: - method of loci, a method in which things to be remembered are placed at different locations in a mental image of a spatial layout Associated images with words - pegword technique - e.g. "one-bun, two-shoe, three-tree, four-door, five-hive, etc." - easy to remember these words in order because they were created by rhyming them with the numbers
How did Kosslyn answer Pylyshyn's criticism with additional experiments?
Size in the visual field experiments - Kosslyn determined if the relationship between viewing distance and the ability to perceive details occurs for mental images - Kosslyn asked participants to image animals next to each other (e.g. elephant and rabbit). - If participants had the elephant fill their visual field, they had slower answers when asked questions about the rabbit. - When the rabbit filled the visual field, participants had faster answers to the questions about the rabbit - asked participants do to mental walk task, in which they imagined walking toward the image. participants had to move closer for small animals than for larger animals just as they would have to do if they were walking toward actual animals.
What is the tacit knowledge explanation of imagery experiments? What experiment was done to counter this explanation?
Tacit knowledge explanation: participants unconsciously use knowledge about the world in making their judgements. Finke and Pinker study countered the explanation - presented four-dot display and asked participants if the arrow is pointed to any of the previously seen dots. Results showed that they took longer to respond for greater distances between the arrow and dot. Participants wouldn't have been able to memorize.
