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Attention & Scene Analysis 1

Attention & Scene Analysis 1. PSY 295 – Sensation & Perception Christopher DiMattina , PhD. Attention. Attention.

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Attention & Scene Analysis 1

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  1. Attention & Scene Analysis 1 PSY 295 – Sensation & Perception Christopher DiMattina, PhD

  2. Attention PSY 295 - Grinnell College - Fall 2012

  3. Attention “Everyone knows what attention is. It is the taking possession by the mind, in clear and vivid form, one out what seem several simultaneously possible objects or trains of thought.” - William James (1890) PSY 295 - Grinnell College - Fall 2012

  4. Attention • Over 100 years later, we don’t have a much better definition • Defined roughly in the book as “any of the large set of selective processes in the brain which restrict processing to a subset of things” PSY 295 - Grinnell College - Fall 2012

  5. General characteristics • Visual attention can be overt or covert • Can be divided (being aware of music while reading) • Can be bottom-up or top-down • Selective attentionis where we attend to one of a variety of different possible stimuli PSY 295 - Grinnell College - Fall 2012

  6. Attention is limited PSY 295 - Grinnell College - Fall 2012

  7. Visual search Often we shift attention to search a crowded scene PSY 295 - Grinnell College - Fall 2012

  8. Eye movements • Overt attention measured by recording eye movements • Depend on both bottom-up and top-down information PSY 295 - Grinnell College - Fall 2012

  9. Salience • An important concept for studying bottom-up attention is that of salience which is vivid a stimulus is relative to its neighbors PSY 295 - Grinnell College - Fall 2012

  10. Saliency map • Neural modeling have been developed to determine which part of a visual image are the most salient • Do good job of predicting human eye movements PSY 295 - Grinnell College - Fall 2012

  11. Attention in space PSY 295 - Grinnell College - Fall 2012

  12. Selective attention in space • Subject fixates central location and simply hits a key as fast as possible when test probe appears PSY 295 - Grinnell College - Fall 2012

  13. Selective attention in space • Prior to appearance of probe, subject cued to probe location • Cue is either valid (matching) or invalid (opposite) PSY 295 - Grinnell College - Fall 2012

  14. Symbolic cues • Instead of spatial cues, Posner also tried symbolic cues • Red spot means right, green spot means left PSY 295 - Grinnell College - Fall 2012

  15. Results • Valid cues reduced reaction times • Invalid cues increased reaction times PSY 295 - Grinnell College - Fall 2012

  16. Results PSY 295 - Grinnell College - Fall 2012

  17. More results PSY 295 - Grinnell College - Fall 2012

  18. Spotlight metaphor • One popular metaphor for top-down attention is a spotlight which focuses on different parts of the visual scene • Things outside of this spotlight are harder to detect – you might be completely oblivious to huge changes in scene! PSY 295 - Grinnell College - Fall 2012

  19. What is changing? NRS 495 - Grinnell College - Fall 2012

  20. What is changing? PSY 295 - Grinnell College - Fall 2012

  21. Spot four differences PSY 295 - Grinnell College - Fall 2012

  22. Spot four differences PSY 295 - Grinnell College - Fall 2012

  23. Change blindness • When you a scene changes with an intervening blank image (or eye movement) you often can miss large changes • This is called change blindness PSY 295 - Grinnell College - Fall 2012

  24. Web activity • http://sites.sinauer.com/wolfe3e/chap7/changeblindF.htm PSY 295 - Grinnell College - Fall 2012

  25. Attention experiment DJ Simons NRS 495 - Grinnell College - Fall 2012

  26. Inattentional blindness • We can literally be blind to aspects of a scene we are not attending to or expecting • In the original experiments by Simons and colleagues, about half of the subjects did not see the gorilla • More difficult attention task caused more people to miss the gorilla, easier task and more people say the gorilla PSY 295 - Grinnell College - Fall 2012

  27. Door experiment • Simons and Levin (1997) on the streets of Ithaca, NY • Asked a stranger for directions • Two construction workers (actually experimenters) carrying a door went between the experimenter and the subject, but one of them switched places with the experimenter • Quite often the subject did not realize the person they were talking to was different!! PSY 295 - Grinnell College - Fall 2012

  28. Visual search and bottom up attention PSY 295 - Grinnell College - Fall 2012

  29. Visual search PSY 295 - Grinnell College - Fall 2012

  30. Vertical red bar ‘pops out’ Time needed to find red bar does not depend on number of distractors PSY 295 - Grinnell College - Fall 2012

  31. Parallel search PSY 295 - Grinnell College - Fall 2012

  32. Conjunction search PSY 295 - Grinnell College - Fall 2012

  33. Conjunction search • Conjunction search is serial instead of parallel • Time to detect target increases with set size PSY 295 - Grinnell College - Fall 2012

  34. Spatial configuration search PSY 295 - Grinnell College - Fall 2012

  35. Feature versus conjunction • Feature searches are parallel and efficient • Conjunction searches are serial and inefficient PSY 295 - Grinnell College - Fall 2012

  36. High level features PSY 295 - Grinnell College - Fall 2012

  37. Web activity • http://sites.sinauer.com/wolfe3e/chap7/vissearchF.htm PSY 295 - Grinnell College - Fall 2012

  38. Finding arbitrary objects is inefficient Find the faucet PSY 295 - Grinnell College - Fall 2012

  39. Scene based guidance Find the faucet PSY 295 - Grinnell College - Fall 2012

  40. Treisman’s feature integration theory • A major problem in sensory neuroscience is the binding problem – different brain areas process different features. How do we put them together? • One proposed solution offered by Treisman is that attention binds features together • Many other possible solutions not involving attention proposed by other scientists PSY 295 - Grinnell College - Fall 2012

  41. Feature integration theory • Limited set of features can be processed pre-attentively • Correct binding requires attention PSY 295 - Grinnell College - Fall 2012

  42. Illusory conjunctions PSY 295 - Grinnell College - Fall 2012

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