ly of
learning by the individual in a great many cases, as in the instinct
of sucking by young animals, pecking for food by young fowls, the
migrating actions of adult mammals and birds, the courting movements
of many varieties of animal species. In all this we have what is
called the "perfect" instinct. To be perfect, an instinct must be
carried out successfully by the animal when his organism is ready,
without any instruction, any model to imitate, any experience to go
upon. The "perfect" instincts are entirely congenital or inborn; the
nervous apparatus only needs to reach the proper stage of maturity or
growth, and forthwith the instinctive action is performed as soon as
the external conditions of life are such as to make its performance
appropriate and useful.

2. On the other hand, many instincts--indeed, probably the greater
number--are not perfect, but "imperfect." Imperfect instincts are
those which do not fully equip the animal with the function in
question, but only take him part way to the goal. He has a spontaneous
tendency to do certain things, such as building a nest, singing, etc.;
but he is not able to do these things adequately or perfectly if left
to himself from birth. This sort of endowment with imperfect instincts
has been the field of some of the most interesting research in animal
psychology, and has led to a new view of the relation of instinct to
intelligence.

3. It has been found that young animals, birds, etc., depend upon the
example and instruction of adults for the first performance of many
actions that seem to be instinctive. This dependence may exist even in
cases in which there is yet a congenital tendency to perform the
action. Many birds, for example, have a general instinct to build a
nest; but in many cases, if put in artificial circumstances, they
build imperfect nests. Birds also have an instinct to make vocal
calls; but if kept from birth out of hearing of the peculiar notes of
their species, they come to make cries of a different sort, or learn
to make the notes of some other species with which they are thrown.

4. The principal agency for the learning of the animals, and for the
supplementing of their instincts, is Imitation. The sight of certain
movements on the part of the adult animals, or the hearing of their
cries, calls, notes, etc., leads the young to fall into an imitation
of these movements or vocal performances. The endowment which such a
young animal has in the