p.37 'In most cases the change which induces a reaction is brought about
by the organism's own movements. These cause a change in the relation of the organism to the environment: to these changes
the organism reacts. The whole behaviour of free-moving organisms is based on the principle that it is the movements of the
organism that have brought about stimulation.' (Jennings.)
p.57 I propose the definition that a form of behaviour is adaptive
if it maintains the essential variables within physiological limits.
p.63 The thesis that 'adaptation' means the maintenance of essential variables
within psychological limits is thus seen to hold not only over the simpler activities of primitive animals but over the more
complex activities of the 'higher' organisms.
p.64 We can now recognise that 'adaptive' behaviour is equivalent
to the behaviour of a stable system, the region of the stability being the region of the phase-space in which all the essential
variables lie within their normal limits.
p.103 I propose, therefore, the thesis that the living organism uses the
principle of ultrastability as an automatic means of ensuring the adaptiveness of its learned behaviour.
p.106 Jennings grasped the fundamental fact that aimless change can lead
to adaptation provided that some active process rejects the bad and retains the good.
p.110 In the previous sections a few simple examples have suggested that
the adaptation of the living organism may be due to ultrastability. But the argument has not excluded the possibility that
other theories might fit the facts equally well. I shall now give, therefore, evidence to show that ultrastability is not
merely plausible but necessary: the organism must be ultrastable.
p.112 In order to be definite about what 'trial and error' implies, here
is the concept defined explicitly:
(1) The organism makes trials only when 'dissatisfied ' or 'irritated' in
some way.
(2) Each trial persists for a finite time.
(3) While the irritation continues, the succession of trials continues.
(4) The succeeding trial is not specially related to the preceding, nor
better than it, but only different.
(5) The process stops at the first trial that relieves the irritation.
p.130 it will be found that some of the ultrastable system's failures
in adaptation occur in situations that are well known to be just those in which living organisms also are apt to fail.
(1) If an ultrastable system's critical surfaces are not disposed
in proper relation to the limits of the essential variables (S. 9/1), the system may seek an inappropriate
goal or may fail to take corrective action when the essential variables are dangerously near their limits.
p.131 (2) Even if the ultrastable system is suitably arranged
- if the critical states are encountered before the essential variables reach their extreme limits - it usually cannot
adapt to an environment that behaves with sudden discontinuities.
p.132 (4) If we grade an ultrastable system's environments according to
the difficulty they present, we shall find that at the 'easy' end are those that consist of a few variables, independent of
each other, and that at the 'difficult' end are those that contain many variables richly cross-linked to form a complex whole.
p.137-138 The learner-driver of a motor-car, for instance, who can only
just keep the car in the centre of the road, may find that any attempt at changing gear results in the car, apparently, trying
to mount the pavement. Later, when he is more skilled, the act of changing gear will have no effect on the direction of the
car's travel. Adaptation thus demands not only the integration of related activities but the independence of unrelated activities.
[JLJ - we have people using cell phones today who cannot both talk and drive.]
p.184 This is what may happen; but will it actually occur?
The tendency to adaptation may be persistent, but why should the process take the favourable course? First we notice
that as adaptation in some form or other is inevitable the only question is what form it will take.
p.240 Ashby, W. Ross. The physical origin of adaptation by trial and error.
Journal of general Psychology, 32, 13 ; 1945.
