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PSYB57 Ch-10.docx

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Dwayne Pare

CH-10 Visual imagery: Use of visual things as basis for making decisions, and as an aid to remembering Introspection about images: - Galton asked people simply to describe their images and rate them for vividness – asked to introspect or “look within” and report their own mental contents - Self report data – form of evidence in which person is asked directly about his or her own thoughts or experiences o Inspect images – just as they would inspect a picture o Description also made it clear that they could “view” images from certain angle o Also reported that they could “read-off” from image details of color/texture - Problem occurred as people could perceive it differently, describe it differently – people are different Chronometric studies of imagery: - Don’t ask to describe images, ask to do something with images and make judgment based on that - Measure time how fast people are in these judgments – gives more accurate imagery portrait - If asked to write detail of image – wont write head/toe – too obvious features; if asked to draw sketch – wont draw claws or nail – too small - For description – features are prominent that are distinctive and strongly associated. For depiction – distinctiveness/association doesn’t matter – size, position determines - Memorize map with landmarks and its position – then formed mental image of map for image scanning procedure – tells that participants scan across their images at constant rate – double scanning distance, double time - Same with Zoom-in (inspect small detail) – response times were directly proportional to amount of zoom required. - Ex. Compare mouse with elephant – relative slow because first needed to zoom in on large to “see” elephant. If compared rat to needle, time would be faster ‘cause it would require no need to zoom-in on needle ‘cause no need to “see” needle – travelling greater distance requires more time - Same rule for Nature of mental image – points close to each other in image vs. points farther apart in scene - Spatial images – images representing geometry of scene depicts scene rather than describing it Mental rotation: - Mental rotation – task in which one first have to imagine one form rotating into alignment with other – once forms are oriented, then can make judgment - Amount of time depends on amount of rotation needed – farther you have to imagine to form rotating, longer evaluation takes - No trouble with rotation in depth, make few errors – however, both cases, the greater degree of rotation, the longer the response time Demand character: - Demand character – cues that might signal how people are supposed to behave in that situation – people in general knows that longer distance takes longer time to travel, hence may create biased results - Experiments should ask participants to make judgment about spatial layout - never mention participants that imagery was relevant to task – diminish demand character and give any cure/suggestion upon “mental travel”–still obtained same results as before – long distance, long time Interaction between imagery and perception: - Parallel between visual and actual visual stimuli – one process occupied with imagining – they should not be available for perceiving - Forming visual image interferes with seeing that forming auditory image interferes with hearing - Less success in detecting weak visual signal if at same time maintaining visual image than maintaining audio image (effect is small but highly reliable) - Less success in detection if maintaining audio image than visualize - Visual images often led to false alarms if trying to detect visual signals, audio images led to false alarms for audio signals - Visualizing H made is easier to perceive H, visualize T – helps perceive T. visualize and perceiving relies on similar mechanisms – one activities primes other - Vision relies on tissue located at occipital area – high activated when examining visual stimulus - Area V1 and V2 cortex – responsible for early stage of visual perception – highly active when maintaining highly detailed image – activation increases higher and higher as imagination gets larger and larger objects - MT/MST - in Brain highly sensitive to motion in visual perception – same area highly active when asked to imagine movement patterns - Brain areas active for recognition of faces – areas also highly active when imagining faces – Area V1 – crucial for both process of visual information and for creation and maintenance of visual images - Brain damage disrupted ability to perceive color – disrupts ability to imagine scenes in color – damage disrupt ability to perceive fine details – disrupt ability to visualize fine detail - In neglect syndrome – when asked imagine and describe all he could “see” in image – listed only ½ side things – neglected half of perceived scene – reported neglected half of imagined scene Sensory effects in imagery: - Neural needed for imagery overlaps with need for perception – if neurons occupied by one function, it will not be available for other – if disrupted/damaged – both activities are compromised – same brain is involved in visualizing as in vision - Imagery and perception shared function – functional equivalence – close parallels in how 2 systems work – how they respond, errors make. Ex. b/w vision and imagery - Visual acuity – ability to see fine detail – in vision, acuity is much greater at center of visual field than visual periphery – showed 2 dots: one far apart from each other, easily see separated – one TOO close together, could not see space between them and seemed to fuse together – shows how well observer can see fine detail - in vision, 2 point acuity greatest when people looking at it directly but what about dots 10 knots away? Acuity fell off dramatically if dots were not in center of vision in both perception and imagery. - Acuity fell dramatically more fast if dots were viewed from above or below, rather than left or right – same results in imagery – imagery matched perception Spatial and visual images: - In tests involving mental rotation or image scanning – blind people showed data same as normal, longer time to respond as longer time to travel/scan - Visual imagery represents arrangement or shape in terms of how things look – spatial imagery – might represent arrangement or shapes in movements, body feelings – more abstract – blind people uses spatial, normal – either - Brain damage – lost color vision – lose ability to imagine scenes in color Lost ability to perceive motion – lost ability to imagine movement Cases in which Brain damage causes issues in imagery, not perception. Ex. Occipital lobe Lesion produced blindness – still did well on most imagery tasks – neglect syndrome in vision, not imagination Visual image
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