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Capacity vs. bottleneck theories

Capacity theory: minds have limitedamount of mental fuel; different tasksshare the amount of mental fuel available

- Can do two tasks in parallel, if enough mentalfuel available

Bottleneck theory: point in informationprocessing where only one piece ofinformation processed at a time

Serial processingonly one thing done at atime

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Cant do them at the same time

Measure RTs: RT to one of the tasks gets

slower and slower the more the two tasks

overlap

SOA

RT2

0

Psychological Refractory Period(Welford, 1967)

Doing one task after the other

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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

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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)

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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)

Measuretime between responding toone task and responding to the other

(Inter-Response Interval or IRI)

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predictions

Bottleneck theory:A

Resp

TASK 1

TASK 2

Hi

Resp

IRI

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Predictions (cont.)

Capacity theory: are doing both tasks at

the same time, just giving more energy to

one or the otherA

Resp

TASK 1

Resp

TASK 2 Hi

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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.

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Results

0

% of

cases

IRI

Support bottleneck because there are no IRIs = 0

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Automaticity

Task repeated enough times where it

apparently no longer requires attention

Driving is a good example

Some tasks can become automatic and

others cant

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Def. of automaticity

Memory for task is not related to whether

youre trying to remember it

More practice doesnt 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)

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example

Reed text, pp. 70-1

LaBerge & Samuels (1974)

People did simple task with regular lettersor 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

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Selective attention

Def.: pay attention to one thing and ignore

something else

Cherry (1950s) created task to measure

peoples ability to do selective attention

Shadowing task = to repeat a message

out loud as you hear the message (to

shadow)

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Selection appears fairly complete

Hear 2 messages simultaneously (one read toeach ear); told to repeat one and ignore theother

Results

people CAN do it; can shadow onemessage and ignore the other

Surprise test of what is remembered from theother, ignored, message: none of the content, or

what language, but could tell it is a language,and did know you heard something and genderof speaker

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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?

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Filter theory

Broadbent (1959)

A bottleneck theory

We filter out one message based on itsearly characteristics (sensation and

perception) and let the other message

through

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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 Ss name within

the ignored message

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predictions

According to early selection, no one

should notice their name in the ignored

message (because youre 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)

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Results

People DO notice their names, supporting

late selection theory