Information Processing, Human Error and the Learning Process 8

Stimuli

The senses, sight, hearing, taste, smell and touch provide inputs (stimuli) to our brain. Most stimuli are stored for a brief time after the input has finished. The ability to retain these stimuli for a short time is essential, as when they first arrive we may not have the processing capacity to deal with them.

Stimuli must be of a certain strength for the sensory receptors to pick them up. In other words, a sound must be of sufficient strength to be received or light level strong enough to perceive. This minimum strength is known as the sensory threshold.

There are three types of memory:

•Sensory memories (sometimes referred to as ultra short-term memories).

•Short-term (working) memory.

•Long-term Memory.

Receptors and Sensory Memories/Stores

The key features of the sensory memories/stores are:

•There is a separate memory store for each sensory system.

•The input decays rapidly.

The sensory stores for touch, taste and smell are of little significance in aviation however those of sight and sound have importance and knowledge of these is necessary. Both of these are discussed.

Sensory Memory for Sound -The Echoic Memory

The longest lasting sensory store is the echoic memory which can last for between 2 and 8 seconds. The echoic memory retains sounds and, for example, it is possible to recall the chimes of a clock that have struck, when realising you want to know the time, but only after the third or fourth stroke.

In these circumstances echoic memory can be interrogated or ‘replayed’ to enable the strokes to be counted consciously. The echoic memory needs to last long enough for input to be scanned for relevance. If an input is of interest then it is called into the short-term memory.

Sensory Memory for Sight -The Iconic Memory

The iconic memory is the visual sensory store and only lasts for between 0.5 and 1 second. 80% of information processed by man enters the visual channel.

Sensory Adaption (Habituation)

A special characteristic of all sensory receptors is that they adapt either partially or completely to their stimuli after a period of time. That is, when a continuous stimulus is first applied, the receptors respond at a very high impulse rate at first, then progressively less rapidly until finally many of them no longer respond at all. This is why, once you get dressed, you do not continue to feel your clothes against the skin.

The classic example of this when, having moved into a house close to an railway line or airport, the noise of passing trains or departing aircraft can cause extreme stress. However, having lived for a month or so under these conditions, the noise may be hardly sensed - if at all. Sensory Adaption is sometimes referred to as habituation.

Information Processing, Human Error and the Learning Process 8

149

8 Information Processing, Human Error and the Learning Process

Process Learning the and Error Human Processing, Information 8

Attention

Introduction

Attention is the deliberate devotion of the cognitive resources to a specific item. Man must be alert to be attentive. But being alert is not sufficient guarantee that attention will be paid to the right item at the right time.

Choice of Item

Due to the limitations of the central processor, we are generally unable to pay attention to a number of different items at any given time. Although attention can move very quickly from item to item, it can only deal with one at a time and thus the need for the pilot to consciously prioritize.

Attention Mechanisms

The reason for the attention mechanisms is because of the two potentially limiting stages in processing information:

•The limit to the number of items held or maintained in short-term memory (sometimes known as working memory).

•Our channel capacity is limited. We cannot devote conscious thought or ‘attend to’ all the stimuli entering our senses.

The Cocktail Party Effect

The limited channel capacity means that there must be a system at an early stage of the whole process to allow us to select those stimuli which will be perceived consciously and used as a basis for our consideration and decisions.

Some stimuli are extremely efficient for getting our attention, for example the cocktail party effect which relates to hearing our own name in a background of many conversations. In aviation this may be hearing our RT callsign among a lot of radio chatter, or detecting a smell of burning on the flight deck. Each will focus our attention in an attempt to get more information.

Types of Attention

Attention is the process of directing and focusing psychological resources to enhance perception, performance and mental experience. It has three characteristics:

•improves mental processing.

•requires effort.

•is limited.

There are two types of attention:

•Selective Attention in which inputs are sampled continually to decide their relevance to the present task at hand, our names or callsigns being particularly attention getting.

•Divided Attention in which our central decision making channel can time-share between a number of tasks. The pilot flying a visual approach will be dividing his attention between looking out to maintain his approach and checking instruments for air speed, height, engines etc. Whereas it would appear that he/she is working on a number of tasks at the same time, in reality, the central processor is spending a fraction of every second on any number of different problems in turn.

150

Information Processing, Human Error and the Learning Process 8

Another example of divided attention is Cherry’s experiment (1950). He arranged for two voices, each carrying different information, to be heard by the subject in either ear at the same time. The subject was unable to process information from both ears at the same time and able only to switch from one voice to the other in turn.

Lack of Attention

It is important to remember that the mind always pays attention to something - except during sleep. Therefore the major danger for pilots is the poor management of attention, that is to say paying attention to the wrong item at any given time.

Stress and Attention

As we have seen in Chapter 7, stress can have a significant effect on attention especially during times of low and high arousal. Our limited ability to process information has implications for the level of performance we are able to achieve.

Low Arousal

At times, such as in the cruise, our attention can wander with the result that information is either missed or misinterpreted. Generating artificial flight deck work loads is a method of addressing this problem.

Optimum Arousal

At this level the central processor is at its most efficient.

High Arousal Overload

At times of high arousal, because of the limited channel capacity of the central processor, there is a real danger of attention becoming narrowed so that important information is disregarded. Indeed, if overloaded, the attention mechanism may even reject additional information. This overload can be of two types:

•Qualitative Overload

The information is perceived to be beyond our attentional capacity and the task too difficult.

•Quantitative Overload

There are just too many responses to be made in the time available.

As we have seen the relationship between workload and performance can be represented as an inverted ‘u’ curve.

Symptoms of Overload

As discussed in the previous chapter when considering stress, the symptoms of overload will vary from individual to individual. Among the most common are:

•A sharp degradation of performance.

•Funnelling of attention or focus.

•Regression.

•Mental “blocks”.

•Mood swings.

•Restlessness.

•Trembling.

•Panic.

Information Processing, Human Error and the Learning Process 8

151

8 Information Processing, Human Error and the Learning Process

Process Learning the and Error Human Processing, Information 8

Perception

Perception involves the conversion of the sensory information received into a meaningful structure. For example, a pattern of vibrations in the air becomes recognized as a particular message. The percept (what we perceive) is not a complete representation of the information in the sensory store but an immediate interpretation of it.

Read the following notice:

Most people on reading the notice will read it incorrectly the first time and perhaps for few more times. The reason in this case is simple. It is the beginning of a well known phrase and, having read the first three lines the reader believes he knows what is coming next and may automatically pass on to the last word to confirm his belief, missing out the extra ‘THE’.

	It is true that we can ‘perceive’ only that which we can
	‘conceive’. It is also true that we perceive only a fraction of
Figure 8.2	the information reaching our senses at any moment. Therein
	lies the importance of the attention mechanism in our model.

The process of perception is greatly assisted by our ability to form mental and three dimensional visual models.

Funnelled Perception

Perception of a situation can differ depending upon the starting point of an observer.

Imagine two men are walking through some woods and they see a family group having a picnic. The first may perceive the overall picture of a family enjoying themselves together in the open air, whereas his companion may first perceive details of the image - the contrast of the colours of the girl’s dress with those of the rug on which she is sitting or, perhaps, the uniqueness of the picnic basket that the family is using.

It is possible, of course, that with time both observers will eventually arrive at the same conclusion; the first narrowing his overall perception to include the details of the scene and the second expanding his perception to include the overall picture. However the initial perception of the two men will be quite different of exactly the same situation.

Perceived Mental Models

Mental Models

We generate a mental model on the basis of past experience and learning, sometimes referred to as the ‘filters of perception’. However, since models are based on our experience which, naturally, differ from person to person, it is true to say that perception is subjective.

We then run that model in a particular situation. The value of these models is that they can reduce the need to attend to all inputs. For example, aircraft RT conversation may be very difficult to understand by the layman. The experienced aviator, with his/her mental model of the order of information in the message and his expectation of the potential content, will have far fewer problems understanding the information.

152