IV. THE FORMATION OF HABITS


Habit in its simplest form is the tendency to do, think, or act as one
has done, thought, or acted in the past. It is the tendency to repeat
activities of all kinds. It is the tendency which makes one inclined to
do the familiar action rather than a new one. In a broader sense, habit
formation means learning. It is a statement of the fact that conduct
_is_ modifiable and that such modifications may become permanent.

The fact of learning depends physiologically on the plasticity of the
nervous system. The neurones, particularly those concerned with
intellectual life, are not only sensitive to nerve currents but are
modified by them. The point where the greatest change seems to take
place is at the synapses, but what this modification is, no one knows.
There are several theories offered as explanations of what happens, but
no one of them has been generally accepted, although the theory of
chemical change seems to be receiving the strongest support at present.
There can be no disagreement, however, as to the effects of this change,
whatever it may be. Currents originally passing with difficulty over a
certain conduction unit later pass with greater and greater ease. The
resistance which seems at first to be present gradually disappears, and
to that extent is the conduct modified. This same element of plasticity
accounts for the breaking of habits. In this case the action is double,
for it implies the disuse of certain connections which have been made
and the forming of others; for the breaking of a bad habit means the
beginning of a good one.

The plasticity of neurone groups seems to vary in two respects--as to
modifiability and as to power to hold modifications. The neurone groups