In the paleontology of character, these fears are the deepest strata, the eocene era, so to speak, of the soul.  They are the hardest to get at and the most silent, as well as the most dominant of the influences which guide conduct.  In Sir Walter Raleigh’s words: 

  “Passions are best likened to streams and floods. 
  The shallows murmur, the deeps are dumb.”

During the first period of childhood, up to five or six, the primary fears group themselves around the taboos and secrets of its life.

Though we have every reason for believing that the sex glands are acting in some way upon the organism during this time, nothing definite is known.  Yet, as the numerous studies of the subconscious recently made prove, sex curiosity like the other curiosities, flowers.  More than about the automatic visceral reactions, these curiosities evoke the repressive imperatives of the associates, the mother and father especially.  These repressive influences may be and often are the effects of ignorance, prudishness, vulgarity, or homosexuality, or the sex perversions that are known as sadism and masochism.  But by the necessities of the case, the sex wishes become overlayed by reflexes associated with the mother and father and close associates as love.  This might be termed the oligocene.  As the circle of acquaintance widens, other loved objects usher in the miocene phases of the development.  With these become interspersed various hates and detestations, deliberately cultivated and accepted by the consciousness.  So we have a cross-slice of the personality in the first five or six years of childhood.

But now, with the onset of the second dentition, a subtle change begins in the endocrine equations of the body.  The second dentition itself is an expression of a certain internal secretion wave passing through the cells, an increase of action of some hormones, a decrease of others.  And a consciousness of physical sexuality appears, while the outlines of character, hitherto mere tracings, become firmer, heavier, quasi-indelible lines.  That there is some activity on the part of the internal secretions of the sex glands, the ovaries and testes, can be demonstrated by accurately charting the behaviour of a boy or girl after this time.  It will be found that there is a cyclic variation of health and conduct, more or less marked of course in each case.  A cold may appear periodically at the end of each month, an increase of irritability and waywardness may be observed, or, on the contrary, a decrease of the regular restless playfulness.  The ghost of sex begins to haunt the scene.