ABSTRACT
Naturally the simpler the organism the simpler will also be the situations experienced. At the bottom of the scale they consist of total undifferentiated responses, in the form of attraction towards what seems to offer satisfaction or repulsion from what proves useless or harmful, which in biology are called tropisms. Instinctive responses, then, are reactions of a more generalised character than purely reflex actions: reactions, that is, in which the response to a particular kind of situation, though always of the same general character, does not always follow exactly the same course. The instinctive tendency, for example, to escape danger by concealment may prompt flight to some place of shelter or may take the form of remaining motionless so as not to attract attention. The compulsion to self-preservation includes all kinds of activity that are concerned with supporting the individual life, and in particular with obtaining food; and also those evoked by whatever offers resistance and causes or threatens harm.
