HUMAN PERFORMANCES AND LIMITATIONS

1. PERCEPTION:

Perception involves the organization and interpretation of sensory data in order to make it meaningful, discarding non-relevant data, i.e. transforming data into information. Perception is a highly sophisticated mechanism and requires existing knowledge and experience to know what data to keep and what to discard, and how to associate the data in a meaningful manner.

A proportion of ‘sensed' data may be lost without being ‘perceived'. An example with which most people are familiar is that of failing to perceive something which someone has said to you, when you are concentrating on something else, even though the words would have been received at the ear without any problem.

The other side of the coin is the ability of the information processing system to perceive something (such as a picture, sentence, concept, etc.) even though some of the data may be missing.

2. ILLUSIONS:

The danger, however, is that people can fill in the gaps with information from their own store of knowledge or experience, and this may lead to the wrong conclusion being drawn. There are many well-known visual ‘illusions' which illustrate the limits of human perception.

• → The Müller – Lyer illusion:

  The Müller-Lyer illusion is an optical illusion consisting of a stylized arrow. When viewers are asked to place a mark on the figure at the mid-point, they invariably place it more towards the "tail" end. It was devised by F.C. Müller-Lyer in 1889.

• Next figure illustrates that we can perceive the same thing quite differently (i.e. the letter “B” or the number “13”). This shows the influence of context on our information processing.

• → The Ebbinghaus illusion:

  In this illusion both orange circles are the same size but they appear different because of their location within a ring of larger/smaller circles.

• → Expectation:

  In aviation maintenance it is often necessary to consult documents with which the engineer can become very familiar. It is possible that an engineer can scan a document and fail to notice that subtle changes have been made.

  He sees only what he expects to see (expectation).

As an illustration of how expectation, can affect our judgment, the same video of a car accident was shown to two groups of subjects. One group were told in advance that they were to be shown a video of a car crash; the other were told that the car had been involved in a ‘bump'.

Both groups were asked to judge the speed at which the vehicles had collided.

The first group assessed the speed as significantly higher than the second group.

Expectation can also affect our memory of events. The study outlined above was extended such that subjects were asked, a week later, whether they recalled seeing glass on the road after the collision. (There was no glass). The group who had been told that they would see a crash, recalled seeing glass; the other group recalled seeing no glass.

3. FACTORS AFFECTING PERCEPTION:

There are several factors that affect an individual's ability to perceive. Some are internal to each person and some are external.

• Physical organism,

• Basic need,

• Goals and values,

• Self-concept,

• Time and opportunity,

• Element of threat.

a) Physical organism:

The physical organism provides individuals with the perceptual apparatus for sensing the world around them. Pilots, for example, must be able to see, hear, feel, and respond adequately while they are in the air. A person whose perceptual apparatus distorts reality is denied the right to fly at the time of the first medical examination.

b) Basic need:

A person's basic need is to maintain and enhance the organized self. The self is a person's past, present, and future combined; it is both physical and psychological. A person's most fundamental, pressing need is to preserve and perpetuate the self. All perceptions are affected by this need.

c) Goals and Values:

Perceptions depend on one's goals and values. Every experience and sensation which is funnelled into one's central nervous system is colored by the individual's own beliefs and value structures.

Spectators at a ball game may see an infraction or foul differently depending on which team they support.

The precise kinds of commitments and philosophical outlooks which the student holds are important for the instructor to know, since this knowledge will assist in predicting how the student will interpret experiences and instructions.

Goals are also a product of one's value structure. Those things which are more highly valued and cherished are pursued; those which are accorded less value and importance are not sought after.

d) Self-concept:

Self-concept is a powerful determinant in learning. A student's self-image, described in such terms as confident and insecure, has a great influence on the total perceptual process. lf a student's experiences tend to support a favorable self-image, the student tends to remain receptive to subsequent experiences. lf a student has negative experiences which tend to contradict self-concept, there is a tendency to reject additional training.

A negative self-concept inhibits the perceptual processes by introducing psychological barriers which tend to keep the student from perceiving. They may also inhibit the ability to properly implement that which is perceived. That is, self-concept affects the ability to actually perform or do things unfavorable.

Students who view themselves positively, on the other hand, are less defensive and more receptive to new experiences, instructions, and demonstrations.

e) Time and opportunity:

It takes time and opportunity to perceive. Learning some things depends on other perceptions which have preceded these learnings, and on the availability of time to sense and relate these new things to the earlier perceptions. Thus, sequence and time are necessary.

A student could probably stall an airplane on the first attempt, regardless of previous experience.

Stalls cannot really be learned, however, unless some experience in normal flight has been acquired. Even with such experience, time and practice are needed to relate the new sensations and experiences associated with stalls in order to develop a perception of the stall. In general, lengthening an experience and increasing its frequency are the most obvious ways to speed up learning, although this is not always effective.

f) Element of threat:

The element of threat does not promote effective learning. In fact, fear adversely affects perception by narrowing the perceptual field. Confronted with threat, students tend to limit their attention to the threatening object or condition. The field of vision is reduced, for example, when an individual is frightened and all the perceptual faculties are focused on the thing that has generated fear.

Flight instruction provides many clear examples of this. During the initial practice of steep turns, a student pilot may focus attention on the altimeter and completely disregard outside visual references. Anything an instructor does that is interpreted as threatening makes the student less able to accept the experience the instructor is trying to provide. It adversely affects all the student's physical, emotional, and mental faculties.