Mica Endsley has categorised SA into three levels: perception, comprehension and projection. These are described further in Table 2.
The more experienced and skilled a pilot, the better his SA at all three levels tends to be. Novice pilots tend to be competent at level 1 SA, but poor at levels 2 and 3.
On the other hand, some skilled and experienced pilots may make errors at the level 2 stage, in that they may perceive the correct information but draw an incorrect conclusion based on previous experience of a similar event.
| Level 1 SA: failure to correctly perceive the situation
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A: Data not available
B: Data difficult to detect/perceive
C: Failure to scan or observe data
1. omission
2. attentional narrowing/distraction
3. high taskload
D. Misperception of data
E. Memory failure
|
| Level 2 SA: Failure to comprehend situation
|
A: Lack of/poor mental model
B: Use of incorrect mental model
C: Over-reliance on default values in model
D: Memory failure
E: Other
|
| Level 3 SA: Failure to project situation into the future
|
A: Lack of/poor mental model
B: Other
|
| General
|
Failure to maintain multiple goals
Habitual schema
|
Table 2: SA Error Taxonomy ( Mica Endsley, 1995 )
Individual factors which can influence SA are those described already in Module 1 on information processing.
Human beings have a limited information processing capability and cannot attend to all sources of information all the time. It is necessary to switch attention from one source to another, often in fairly rapid succession, and store the information in memory. Appropriate training can help pilots develop and practice good 'attention sampling' strategies, to ensure that one or more sources of information do not get neglected.
A simple example of this is the instrument scanning pattern which many pilots learn at an early stage in their flying training, in order not to miss a potentially important source of information.
Working memory capacity is a limit on SA, since its capacity can soon be overwhelmed when used to store perceived information, comprehending the meaning of that information, combining it with existing knowledge to achieve a composite picture, and predict future outcomes whilst still maintaining a good appreciation of the current situation.
The load on working memory and processing capabilities can be reduced as tasks become more and more automatic, with the development of skill. However, this very 'automaticity' can have a down side in that it can lead to failure to perceive new stimuli (e.g. hearing what you expect to hear, or seeing what you expect to see).
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