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Psychological Refractory Period Task Switching

Outline. PRP ParadigmLocus-of-Slack LogicGeneral PRP FindingsExample ExperimentTwo Bottlenecks or One?Johnston, McCann

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Psychological Refractory Period Task Switching

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    1. Psychological Refractory Period & Task Switching

    3. “Understanding multitask interference provides clues to cognitive architecture and the control of mental processes” (McCann & Johnston, 1992, p. 471) Overarching Cause

    4. Psychological Refractory Period aka: the PRP Paradigm

    5. Past research Continuous tasks (e.g. shadowing) support capacity models input processing output

    6. Past research Continuous tasks (e.g. shadowing) support capacity models input processing output but can be explained by bottleneck models if we assume perceptual buffers, response buffers & high frequency switching

    7. A more definitive empirical test needs: Precise time measurement of stimuli & responses Responses traceable to specific stimuli stimulus 1 response 1 stimulus 2 response 2

    8. A more definitive empirical test needs: Precise time measurement of stimuli & responses Responses traceable to specific stimuli stimulus 1 response 1 stimulus 2 response 2 Such a paradigm was used in 1952 by Welford, but since 1989 has been used with improved technology

    9. Terminology Response Time of Task 1 = RT1 Response Time of Task 2 = RT2

    10. Terminology Response Time of Task 1 = RT1 Response Time of Task 2 = RT2 Early (Pre-central), Central & Late (Post-central) processing for each task: Task 1 includes A1, B1 & C1 Task 2 includes A2, B2 & C2 Task 1: RT1 S1 A1 B1 C1 R1

    12. Robustness of Psychological Refractory Effect Occurs when: Both tasks are very simple (e.g. high / low tone & letter / number) Each stimulus and response uses a different sensory modality (e.g. auditory-vocal & visual-manual)

    13. Models of Central Attention

    16. Locus-of-Slack Logic

    17. Long SOA:

    18. Long SOA: Short SOA:

    19. Long SOA:

    20. Long SOA: Short SOA:

    22. Long SOA:

    23. Long SOA: Short SOA:

    25. What is in the Bottleneck?

    26. Everyday Life People can often do two tasks that are more complex than those used in PRP experiments at the same time: Driving & having a conversation Reading & listening to music Etc. Explanations: One of the tasks is so well practiced, it requires no processing capacity Switching b/w tasks is too fast to be noticeable

    27. Example Experiment: McCann & Johnston (1992)

    28. Method S1: high or low tone S2: R2:

    30. Two Types of Attention? Johnston, McCann & Remington (1995)

    31. Overarching Cause “Although our senses respond to numerous stimuli simultaneously, selective attention permits only a few of them to gain access to deep levels of cognitive processing, where they can control overt responses” (p. 365) “Is selective attention accomplished by a unitary process or by several distinct processes?” (p. 365)

    32. Spatial Cuing Paradigm Validly cued trial Invalidly cued trial ? Faster RT ? Slower RT

    33. 2 Paradigms = 2 Findings = 2 Attentions Spatial cuing paradigm: P cued to a location where target stimuli do (= fast RT) or do not (= slow RT) appear ? Attention operates at an early stage of processing: “input attention” PRP paradigm: 2 speeded tasks - slower RT2 at shorter SOA ? Attention operates at a relatively late stage: “central attention”

    34. Unparsimonious: 2 Attentions = 2 Findings More parsimonious: 2 Tasks + 2 Stimulus sets = 2 Findings If: 1 task + 1 stimulus set + 1 processing stage = 2 findings Then: 2 attentions = more parsimonious

    35. Letter Identification Location of stage: after stage where input attention operates before stage where central attention operates

    36. Letter Identification Location of stage: after stage where input attention operates before stage where central attention operates Manipulate length of letter identification stage by altering stroke arrangement: Easy: Hard:

    37. Experiment 1 - PRP T1. S1: 300 / 900 Hz tone R1: verbal (“high” or “low”) T2. S2: A or H (normal or distorted) R2: manual (keyboard) SOA: 50, 150, 450, 600 ms 24 P’s 128 practice trials & 384 experimental

    39. Results Exp’t 1: Underadittivity of SOA & letter distortion ? letter identification is before central attention bottleneck

    40. Experiment 2 – Spatial Cuing 22 P’s 40 practice trials & 360 experimental

    42. Results Exp’t 1: Underadittivity of SOA & letter distortion ? letter identification is before central attention bottleneck Exp’t 2: Additivity of spatial cuing & letter distortion ? letter identification is after input attention bottleneck

    43. “If only one type of attention occurs in both paradigms, why can letter identification be carried out concurrently with the diversion of attention to the auditory task in Experiment 1, but not be carried out concurrently with the diversion of attention to the invalid visual cue in Experiment 2?” (p. 369)

    44. What have we learnt?

    45. What have we learnt?

    46. What have we learnt?

    47. Conclusions If the brain consists of numerous relatively autonomous processing modules, then maybe some form of “attention” is a property of every processor in the brain, just like some form of memory is now believed to be. If attention = limited processing capacity then this is a truism

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