Presentation on theme: "Capacity vs. bottleneck theories"— Presentation transcript:
1 Capacity vs. bottleneck theories Capacity theory: minds have limited amount of mental fuel; different tasks share the amount of mental fuel availableCan do two tasks in parallel, if enough mental fuel availableBottleneck theory: point in information processing where only one piece of information processed at a timeSerial 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 toneE.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 overlapPsychological Refractory Period(Welford, 1967) Doing one task after the otherRT2SOA
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 accuratelyThe 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 tasksTwo 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)
8 Predictions (cont.)Capacity theory: are doing both tasks at the same time, just giving more energy to one or the otherATASK 1RespTASK 2“Hi”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 Results Support bottleneck because there are no IRIs = 0 % of cases % ofcasesIRISupport bottleneck because there are no IRIs = 0
11 AutomaticityTask repeated enough times where it apparently no longer requires attentionDriving is a good exampleSome tasks can become automatic and others can’t
12 Def. of automaticityMemory for task is not related to whether you’re trying to remember itMore practice doesn’t help; hard to change how you do the taskCan 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 lettersAt first, people not very good working with new lettersWith enough practice, people are as good with new letters as with regular letters
14 Selective attentionDef.: pay attention to one thing and ignore something elseCherry (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 otherResults people CAN do it; can shadow one message and ignore the otherSurprise 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 youUsed shadowing technique: hearing one message and ignoring anotherTrick: secretly place the S’s name within the ignored message
19 predictionsAccording 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 ResultsPeople DO notice their names, supporting late selection theory
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