simplest, recognizes only this emotional type: "A complex is a system
of connected ideas, having a strong emotional tone, and displaying a
tendency to produce or influence conscious thought and action in a
definite and predetermined direction."[24]

[Footnote 24: Frink: "What Is a Complex?" _Journal American Medical
Assoc_., Vol. LXII, No. 12, Mar. 21, 1914.]

Emotion and repetition are the great welders of complexes. Emotion is
the strongest cement in the world. A single emotional experience
suffices to bind together ideas that were originally as far apart as
the poles.

Sometimes a complex includes not only ideas, movements, and emotions,
but physiological disturbances and sensations. Some people cannot go
aboard a stationary ship without vomiting, nor see a rose, even though
it prove to be a wax one, without the sneezing and watery eyes of
hay-fever. This is what is known as a "conditioned reflex." Past
associations plus fear have so welded together idea and bodily
manifestation that one follows the other as a matter of course, long
after the real cause is removed. In such ways innumerable nervous
symptoms arise. The same laws which form healthy complexes, and,
indeed, which make all education possible, may thus be responsible for
the unhealthy mal-adaptive association-habits which lie back of a
neurosis. Fortunately, a knowledge of this fact furnishes the clue to
the re-education that brings recovery.

A complex may be either conscious or unconscious, but as it usually
happens that either all or part of its elements are below the surface,
the word is oftenest used to mean those buried systems of the