[Footnote 59:  Sidis:  Foundations of Normal and Abnormal Psychology, Chap.  XXX.]

Each organism has a wide field of choice as to which ideas and which physical stimuli it shall welcome and which it shall shut out.  We may raise our thresholds, build up a bulwark of indifference to a whole class of excitations, shut our mental doors, and pull down the shades; or we may lower the thresholds so that the slightest flicker of an idea or the smallest pin-prick of a sensation finds ready access to the center of attention.

=Thresholds and Character.= There are certain thresholds made to shift frequently and easily.  When one is hungry any food tastes good, for the threshold is low; but the food must be most tempting to be acceptable just after a hearty meal.  On the other hand, a fairly constant threshold is maintained for many different kinds of stimuli.  These stimuli are always bound together in groups, and make appeal depending upon the predominating interest.  As anything pertaining to agriculture is noticed by a farmer, or any article of dress by a fashionable woman, so any stimulus coming from a “warm” group is welcomed, while any from a “cold” group is met by a high threshold.  The kind of person one is depends on what kind of things are “warm” to him and what kind are “cold.”  The superman is one who has gained such conscious control of his psychic thresholds that he can raise and lower them at will in the interests of the social good.

=Thresholds and Sensations.= The importance of these principles is obvious.  The next chapter will show more of their influence on ideas and emotions; but for the present we will consider their lessons in the sphere of the physical.  Psychology speaks here in no uncertain terms to physiology.  Whoever becomes fascinated by the processes of his own body is bound to magnify the sensations from those processes, until the most insignificant message from the subconscious becomes a distressing and alarming symptom.  The person whose mental ear is strained to catch every little creaking of his internal machinery can always hear some kind of rumble.  If he deliberately lowers his thresholds to the whole class of stimuli pertaining to himself, there is small wonder that they sweep over the boundaries into consciousness with irresistible force.

=The Motives for Sensitiveness.= Sensitiveness is largely a matter of choice, but what determines choice?  Why is it that one person chooses altruism as the master threshold that determines the level of all the others, while another person who ought to be equally fine lowers his thresholds only to himself?  What makes a person too interested in his own sensations and feelings?  As usual there is a cause.

The real cause back of most cases of chronic sensitiveness is an abnormal desire for attention.  Sometimes this love of attention arises from an under-developed instinct of self-assertion, or “inferiority complex.”  If there is a sense of inadequacy, a feeling of not being so important as other people, a person is quite likely to over-compensate by making himself seem important to himself and to others in the only way he knows.  All unconsciously he develops an extreme sensitiveness which somehow heightens his self-regard by making him believe himself finely and delicately organized, and by securing the notice of his associates.