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ATTENTION!!!

From page 147 of Wickens et al.

ATTENTION RESOURCES

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ATTENTION!!!

A "flexible, sharable, processing resource of limited availability".

Our ability to attend to several things at once (time-sharing) depends on: Controlled vs automatic processing Skill Which resource(s) required

Attention “tasks” can be divided into 4 categories ...

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1. Selective Attention

"requires the monitoring of several channels (sources) of information to perform a single task.” Example: scanning cockpit instruments

Limitations: – As the number of channels of information increases, performance

declines (even when the overall signal rate is the same).– Can select inappropriate aspect(s) of the environment to process.– "Cognitive tunnel vision" in complex environments with many

displays, especially under stress. (Example: 1972 Eastern Airlines crash in the Everglades).

Errors associated with Selective Attention are generally the result of an intentional, but unwise choice.

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Selective Attention

Design Guidelines:

Place frequently sampled displays together.

Place sequentially sampled displays together.

Use external aids/reminders to help people remember when the display was last sampled.

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2. Focused Attention Requires attending to one source of information at the

exclusion of all others Examples:

Trying to study while someone else is talking on the phone Trying to enter numerical data into Excel while others are discussing

basketball scores and stats.

Limitations: Impossible to ignore a visual stimulus within 1 degree of visual

angle of the visual information you are interested in. Auditory stimuli sufficiently loud with respect to the signal you

are interested in, and/or similar to it, can interfere with the signal.

Errors associated with focused attention are generally unintentional, driven by the environment.

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Focused Attention

Design Guidelines: Parallel vs serial processing

Parallel processing is helpful when: two tightly coupled tasks are performed simultaneously

e.g., control roll and pitch of aircraft two or more information sources imply common action (redundancy

gain)

Parallel processing is harmful when similar aspects of different stimuli must be processed (resource

competition) e.g., listen to air traffic control and input waypoints into the onboard

computer two or more stimuli imply different actions

e.g., a batter distracted by a moth

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3. Sustained Attention

"the ability of observers to maintain attention and remain alert over prolonged periods of time." Example: Security guard watching monitor for intruders.

Limitations: Vigilance decrement - a decline in the speed and accuracy of

signal detection with time on the task (found more in the laboratory than in real world tasks).

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Sustained Attention

Design Guidelines:

Appropriate work-rest schedules and task variation.

Increase the conspicuity of the signal.

Reduce uncertainty as to when and where.

Training.

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4. Divided Attention

"two or more separate tasks must be performed at the same time, and attention must be paid to both.” Example: Driving and talking to a passenger.

Limitations: Time-sharing ...

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The Resource Metaphor of Attention Time-sharing (or doing two tasks simultaneously) is

difficult because we have limited attention resources.

The Performance-Resource Function (PRF)

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The Performance Operating Characteristic (POC)

Performance Operating Characteristic Curve

0

0.5

1

1.5

-0.5 0 0.5 1 1.5

Task A

Tas

k B

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Limitations of the "single-resource" theory of attention Difficulty insensitivity

In some experiments it has been shown that making one time-shared task more difficult has no effect on the performance of the other.

Perfect time-sharing

Structural alteration effects In some experiments it has been shown that altering the structure

(but NOT the difficulty) of one task affects performance on the other.

Example: Manual vs vocal responses to a tone discrimination task while tracking.

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Multiple-Resource Theory

Instead of one "pool" of resources, there are several different capacities of resources:

Codes: spatial or verbal

Modalities: visual or auditory

Stages of processing: early (encoding/central processing) or late (responding)

The more resources are shared, the more tasks will interfere.

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Multiple-Resource Theory

To the extent that tasks demand separate rather than common resources: Time-sharing will be more efficient Difficulty insensitivity will be observed The POC will be more "boxy"

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Limitation of Multiple Resource Theory The three proposed dimensions (stages, codes,

modalities) do not account for all experimental findings. For example: Tasks with different rhythmic requirements are hard to time-share.

Control dynamics affect the efficiency of time-sharing a manual tracking task with another task.

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Implications & Design Recommendations Since spatial and verbal codes draw upon separate

resources, time-sharing manual and verbal responses is highly efficient (assuming that the manual response is spatial in nature and that the vocal response is verbal). Example:

pilots fly the airplane (spatial, manual task) and simultaneously talk to air traffic control (verbal, vocal task).

This example also demonstrates different modalities (visual and auditory) which also draw from separate resources;

therefore …

Design systems to support a mix of manual and vocal responses for time-shared tasks.

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Multiple Resource Theory The effect of training

Training can make tasks data limited rather than resource limited

Data limited tasks can coexist more easily than resource-limited

Reasoning behind “part-task training” paradigms

People can also be trained to timeshare tasks more efficiently

Rapid switching between tasks True multi-tasking