Cybernetics is defined as ``[...] the study of control and communication in the machine or in the animal [...]'' . In the current context, we will use the term cybernetics in a narrower sense, i.e., as referring to the study of control systems. The communication and information-theoretical aspects that were originally partly embedded in cybernetics, are currently studied in a different field, called informatics or computer science. The name cybernetics comes from the Greek word for steersman (), and in fact does not have connotations with respect to communication or information. More specifically, even, we will only speak of systems controlling a physical parameter. The following quotation clarifies how Wiener himself envisaged the control problem:
``[...] what we will is to pick the pencil up. Once we have determined on this, our motion proceeds in such a way that [...] the amount by which the pencil is not yet picked up is decreased at each stage [...]''Since the development of technical servo systems , the interest in cybernetics as a paradigm has been increasing and fading in a number of fields, varying from engineering, biology and psychology to economics. Research in cybernetics has led to powerful mathematical tools and theoretical concepts, gathered under the heading of Control Theory.
[362, page 14,]
In theories on motor control, this ``Closed loop model'' considers the
sensorial feedback (tactile and/or acoustic) to be the intrinsic source of
control, e.g., of the articulatory activities during speech or
handwriting production. The articulatory trajectories are planned on-line
depending on the measured feed-backs until the target (spatial or acoustic)
is reached. Although this model can explain a number of phenomena in motor
control, its basic shortcoming is the fact that propagation delays in the
biological system are substantial, necessitating other concepts to explain
principles like feedforward, predictive control.
Table 3.1 : Typical reaction times
Table 3.2 : Typical delay times