Vigilance

Question 1

What is vigilance or “sustained attention”?

Answer 1

The ability to maintain attention and remain alert to stimuli over prolonged periods of time.

Question 2

Where did vigilance research originate?

Answer 2

In World War II, when the Royal Air Force (RAF) commissioned Norman Mackworth to investigate why radar operators were missing enemy submarines.

Question 3

What are five theories of vigilance?

Answer 3

• Inhibition theory
• Filter theory
• Arousal theory
• Expectancy theory
• Memory Load

Question 4

Describe the inhibition theory of vigilance.

Answer 4

It was proposed by Mackworth (1950). He compared the vigilance decrement to the “extinction function” of a conditioned response when no longer reinforced (unrewarded responses).

Question 5

Describe the filter theory of vigilance.

Answer 5

It was proposed by Broadbent (1958). The vigilance decrement occurs when this filter fails to periodically take in task relevant information as a result of its biases (filtering deviations)

Question 6

Describe the arousal theory of vigilance.

Answer 6

It was proposed by Frankmann and Adams (1962). They believed that the nature of monotonous tasks in might reduce the level of nonspecific cortical activity necessary in maintaining continual alertness. Davies, Parasuraman, and Toh (1984) tested this theory by testing subjects during morning and afternoon sessions to determine the effect of tonic arousal on vigilance decrement.

Question 7

Describe the expectancy theory of vigilance.

Answer 7

It was proposed by Baker (1959, 1963). He suggested that the observer’s detection rate is determined by the expectancy level which is influenced by the probability and regulation of signal occurrence.

Question 8

Describe the memory load theory of vigilance.

Answer 8

It was proposed by Parasuraman (1979). He suggested that the vigilance decrement in low event rate resulted from an increase in response criterion which might be linked to Target Expectancy. However, in high event rate vigilance tasks, the vigilance decrement caused by a loss in perceptual sensitivity might be linked to Capacity Limitations imposed by memory load (Parasuraman, 1979; Fisk & Schneider, 1981), signal discriminability (Parasuraman & Mouloua, 1987), or stimulus encoding (Nuechterlein et al., 1983).

Question 9

What is the vigilance decrement or decrement function?

Answer 9

For tasks involving low-probability signals and long periods of watch, it is the decline of monitoring performance over time as a function of time on task.

Question 10

Describe the first vigilance experiment?

Answer 10

Mackworth (1948) created a task, called the “clock test”, in which a pointer moved clockwise around a clock at a rate of one movement per second. Occasionally, this pointer executed a “double jump”. This “jump” was considered to be a signal. Individuals were instructed to indicate whenever a “double jump” occurred. RAF Personnel were tested (with 12 signals occurring every 30 minutes) for 2 hours. He found that performance declined from 95% to 75%, then to 70% for the remainder of the 2-hour vigil.

Question 11

What are the four major task dimensions of the vigilance taxonomy proposed by Parasuraman and Davies (1977)?

Answer 11

• Signal discrimination type (successive or simultaneous, sensory or cognitive)
• Event rate (low or high)
• Sensory modality (auditory or visual)
• Source complexity

Question 12

What is the difference between a successive and a simultaneous discrimination task?

Answer 12

Successive discrimination - when the comparison is distributed across time. That is, the individual is first presented with what the signal/target is, and then at a later time must decide whether a signal/target is present. This type of discrimination is highly dependent on memory (either short term, long term, or working memory depending on the given task). These are also described as effortful, as requiring controlled processing, and as requiring access to working memory.

Simultaneous discrimination - when the comparison occurs at the same time. That is, the individual has the reference signal/target available to them at the same time that they are deciding whether a signal/target is present. This type of discrimination is less dependent on memory. These are also described as effortless, automatic, and as not requiring working memory.

Question 13

Which types of vigilance tasks are considered low event rate and which are considered high event rate?

Answer 13

Low-event rate

• Vigilance tasks that are low event rate have less than (<) 24 events per minute
• In low event rate tasks, vigilance decrement is linked to an increase in response criteria (more liberal beta)

High-event rate

• Vigilance tasks that are high event rate have more than (>) 24 events per minute
• In high event rate tasks, vigilance decrement has been linked to a loss in perceptual sensitivity (d’).

Question 14

What other sensory modality has been considered in the vigilance taxonomy?

Answer 14

• Haptic/Tactile

Question 15

Describe the NASA MAT (Multi-Attribute Task) Battery

Answer 15

Three tasks that simulate all actions needed for a pilot to fly an aircraft

• System monitoring - a monitoring task window which includes gauges and warning lights
• Tracking - a tracking task window for the demands of manual control
• Resource management - a resource management task window which permits maintaining target levels on a fuel management task
• Communication - a communication task window to simulate air traffic control communications

The system monitoring task is the investigated one because monitoring has moved from a manual to a fully automated function more often than not. We are now often supervisors and not active operators like we used to be.