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Capacity vs. bottleneck theories

Explore how capacity theory posits limited mental fuel for tasks, while bottleneck theory suggests processing bottlenecks affecting task performance. Learn about dual-task experiments, automaticity, selective attention, and filter theory in cognitive psychology.

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Capacity vs. bottleneck theories

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  1. Capacity vs. bottleneck theories • Capacity theory: minds have limited amount of mental fuel; different tasks share the amount of mental fuel available • Can do two tasks in parallel, if enough mental fuel available • Bottleneck theory: point in information processing where only one piece of information processed at a time • Serial processing  only one thing done at a time

  2. Simple dual-task experiment • Have people do two very simple tasks at the same time (2 choice RT tasks) • E.g., task 1 = hear a tone, press a key to signify HI or LOW pitch tone • E.g., task 2 = see a letter, press a key (with other hand) to signify “A” or “B” • Can you do them at the same time?

  3. Can’t do them at the same time • Measure RTs: RT to one of the tasks gets slower and slower the more the two tasks overlap Psychological Refractory Period (Welford, 1967)  Doing one task after the other RT2 0 SOA

  4. More on capacity theory • Sometimes, when you try to do more than one thing at a time, you exceed your mental fuel (capacity), and still do tasks just slower and less accurately • The more capacity given to task, the faster and more accurate your performance will be

  5. Capacity interpretation • Maybe people slow down on the second task (RT2) because they give less capacity to that task and more to the first task (Task 1)

  6. Pashler (1996) • [capacity theory developed Kahneman, 1973] • Have people do two simple tasks • Two tasks always happen at exactly the same time (SOA = 0 ms) • Measure – time between responding to one task and responding to the other (Inter-Response Interval or IRI)

  7. predictions • Bottleneck theory: IRI A TASK 1 Resp “Hi” TASK 2 Resp

  8. Predictions (cont.) • Capacity theory: are doing both tasks at the same time, just giving more energy to one or the other A TASK 1 Resp “Hi” TASK 2 Resp

  9. More on capacity prediction • Will be variability in the IRIs because people will devote varying amounts of energy to task 1 and task 2 each time they do it.

  10. % of cases 0 Results IRI Support bottleneck because there are no IRIs = 0

  11. Automaticity • Task repeated enough times where it apparently no longer requires attention • Driving is a good example • Some tasks can become automatic and others can’t

  12. Def. of automaticity • Memory for task is not related to whether you’re trying to remember it • More practice doesn’t help; hard to change how you do the task • Can do this task and another task at the same time (no capacity nor bottleneck) • Hasher & Zacks (1979)

  13. example • Reed text, pp. 70-1 • LaBerge & Samuels (1974) • People did simple task with regular letters or strange new letters • At first, people not very good working with new letters • With enough practice, people are as good with new letters as with regular letters

  14. Selective attention • Def.: pay attention to one thing and ignore something else • Cherry (1950s) created task to measure people’s ability to do selective attention • “Shadowing task” = to repeat a message out loud as you hear the message (to shadow)

  15. Selection appears fairly complete • Hear 2 messages simultaneously (one read to each ear); told to repeat one and ignore the other • Results  people CAN do it; can shadow one message and ignore the other • Surprise test of what is remembered from the other, ignored, message: none of the content, or what language, but could tell it is a language, and did know you heard something and gender of speaker

  16. When does the selection happen? • Early processes are sensation, perception, etc. • Late processes start with memory, thinking, problem-solving, etc. • Question: Early or late selection?

  17. Filter theory • Broadbent (1959) • A bottleneck theory • We “filter” out one message based on its early characteristics (sensation and perception) and let the other message through

  18. Moray (1959) • Cocktail party effect: trying to pay attention to your conversation while ignoring conversations around you • Used shadowing technique: hearing one message and ignoring another • Trick: secretly place the S’s name within the ignored message

  19. predictions • According to early selection, no one should notice their name in the ignored message (because you’re not processing the meanings of the words) • According to late selection, people will hear their names (because you ARE processing the meanings of the words)

  20. Results • People DO notice their names, supporting late selection theory

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