Humans and Machines

In the technologists’ view, humans have certain physiological, psychological, and sociological characteristic that define their capabilities and limitation in the work situation. These characteristics are thought of not as fixed quantities but as distributions that reflect individual variation.

In performing work, human functions are envisioned in three general classifications:

1. Receiving information through the various sense organs.
2. Making decisions based on information received and information stored in the memory of an individual.
3. Taking action based on decisions. In some instances, the decision phase may be virtually automatic because of learned responses, as with a highly repetitive task. In others, the decisions may involve extensive reasoning and the results may be complex.

Note that the general structure is that of a closed-lop automated system. Where in is the difference? Are automated machines like humans? Yes, in this model of humans in the system, machines and humans are alike in certain important respects. Both have sensors, stored information, comparators, decision makers, effectors, and feedback loops. The difference is in the humans’ tremendous range of capabilities and in the limitations imposed by physiological and sociological characteristics. Thus, machines are much more specialized in the kinds and ranges of tasks they can perform. Machines perform tasks as faithful servants reacting mainly to physical factors. Humans, however, react to their psychologists and sociologists environments as well as to the physical environment.

Conceptual Framework for Human – Machine Systems:

Humans and machines can have equally tough tasks when performing similar functions in work tasks, although they each have comparative advantages.

Information is received by the sensing function. Sensing by humans is accomplished through the sense organs. Machines sensing can parallel human sensing through electronics or mechanical devices. Machine sensing is usually much more specific or single purpose in nature than is the broadly capable human sensing.

Information storage for humans is provided by memory or by access to records. Machine information storage can be obtained by magnetic tape, or disk, punched cards, and cams and templates.

The function of information processing and decision making is to take sensed and stored information and procedure a decision. The processing could be as simple as making a choice between two alternatives, depending on input data, or very complex involving deduction, analysis, or computing to produce a decision for which a command is issued to the effecter.

The effecter or action function occurs as a result of decisions and commands and may involve the triggering of control mechanisms by humans or machines or a communication of decisions. Control mechanisms would, in turn cause something physical to happen, such as moving the hands or arms, starting a motor, or increasing or decreasing the depth of a cut on a machine tool.

Input and output are related to the raw materials or the material being processed. The output represents some transformation of the input. The processes themselves may be of any type: chemical processes to change shape or form, assembly, transport or clerical.

Information feedback concerning the output states is an essential ingredient because it provides the basis for control. Feedback operates to control the simplest hand motion through the senses and the nervous system. For machines, feedback concerning the output states provides the basis for machine adjustment are automatic (closed loop automation). When machine adjustment are only periodic, based on information feedback, the loop is still closed but not on a continuous and automatic basis. Obviously, automation is the ultimate in the technological view of job design.