Potenttalities in the Control of Behaviour 
Objection has been raised to calling such mechanisms purposive, 
since their purpose has been built into them by man. But man 
himself and his behaviour are the result of purely fortuitous 
mutations acted upon by natural selection. Natural selection 
that has produced purposive human behaviour is itself a non- 
purposive process. 
Whereas feedback devices of control have developed rapidly 
in engineering in the past twenty years as a product of social 
evolution, biological evolution by natural selection brought 
such mechanisms to a high order of development several hun- 
dred million years ago with the evolution of synaptic nerve nets 
and central nerve ganglia. Regulation of patterned contraction 
of muscles for orderly behaviour, ranging from rhythmic inter- 
actions of respiratory muscles, to the control of posture of the 
limbs and the control of muscles of speech, involves central 
nervous mechanisms regulated by negative feedback. ‘Thus 
the brain sends motor impulses to contract muscles; the con- 
traction stimulates sense organs in the muscle which sends 
impulses over sensory fibres back to the central nervous system 
informing it of the degree of muscle action; the central control 
centre responds by modulating, increasing or inhibiting further 
motor output. The constancy of control of our internal environ- 
ment, the control of hormone balance, heat regulation, cardio- 
vascular control, the balanced activity of groups of cells in the 
central nervous system—cord, brain stem, reticular formation, 
cerebellum, basal ganglia, and cerebral cortex—are examples of 
mechanisms controlled by negative feedback. All co-ordinated 
behaviour, conscious and unconscious, uses these mechanisms— 
without them organized purposive behaviour would be im- 
possible. The behaviour of the organism as a whole in adjusting 
to its external environment is controlled by information fed 
back to it in response to its behaviour—words are spoken and 
acts performed producing responses from the environment, 
including our fellows, and these responses act as feedback to 
modify one’s behaviour further. 
Feedback to the organism of information from its external 
environment determines learning and conditioning via 
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