when it does not appear till some time after birth, for the chance of
acquiring it by a process of learning has to be taken into account. If
you can so control the conditions under which the young individual
grows as to eliminate the possibility of learning a certain act, then
you can {93} make sure whether the act is acquired or provided by the
native constitution.

Experimental Detection of Native Reactions

Take the question whether birds learn to fly or simply come to fly
when their natural development has gone far enough. The newly hatched
bird cannot fly; its muscles are not strong enough, its wings are not
feathered, and its nerve mechanism for cooerdinating the wing movements
has still some growth to make before being ready for use. But, under
ordinary conditions, the young bird has some chance to _learn_ flying,
by watching the old birds fly and by trying and gradually getting the
motion. The old birds, after a time, push the young ones from the nest
and seem, to our eyes, to be teaching them to fly. Experiment enables
us to decide the question. One of the earliest experiments in animal
psychology was made by Spalding in 1873. He took newly hatched birds
from the nest and shut each one separately in a little box that gave
it no chance to stretch its wings or to see other birds fly. Here he
fed and cared for them till the age at which flying usually begins,
and then released them. Off they flew, skilfully managing wings and
tail, swooping around the trees and soon disappearing from sight. A
very successful experiment!--and conclusive. The little birds had had
no chance to learn to fly, yet they flew. Flying must have come to
them in the natural course of growth.

Compare with this experiment another one no less successful, though it
turned out differently. To discover whether the song of the oriole is
fixed by nature or learned by imitation, Scott took some little ones,
just hatched, and brought them up away from older birds. After a time,
when growth had advanced to a certain stage, the birds began {94} to
sing. The elementary notes and rattles characteristic of the oriole
made their appearance, but were combined in unusual ways, so that the
characteristic song of the oriole did not appear, but a new song. When
these birds had grown up in the laboratory, other new-hatched orioles
were brought up with them, and adopted this new song; so that the
laboratory became the center for a new school of oriole music