ABSTRACT
IN the last Chapter, we have stressed the biological determination of certain aspects of behaviour, and, in particular, in relation to introversion-extraversion, we have concentrated on such hypothetical constructs or intervening variables as excitation and inhibition. Is it possible to go a little further still and identify some actually recognizable physical structures in the brain as, in turn, underlying these variables? Eysenck (1963b) has suggested the possibility that different parts of the so-called reticular formation may be in part responsible for the phenomena of excitation and inhibition, and a brief presentation of this theory will now be given.
