ust be traversed by nerve currents
in order to arouse the muscles to this particular act are not, we may
suppose, all ready at the same instant, and it takes some little time
for them to pass from {97} the stage when they will first conduct to
the stage when, having grown more, they conduct perfectly. In other
words, the neural mechanism for walking can function imperfectly
before it can function perfectly. It takes several weeks of growth to
pass from the barely functional condition to the fully functional
condition; and it is during these weeks that the child seems to be
learning to walk, while really his exercise of the partially developed
neural mechanisms has no effect except to hasten their growth to some
extent.

Universality as a Criterion of Native Reactions

The fundamental sign or criterion of a native trait, in accordance
with what we have been saying, is that it shall make its appearance
when there has been no chance to acquire it through experience. This
is the one perfect criterion; but unfortunately it cannot always be
applied, especially with a slowly maturing and much-learning species
such as the human. We need other criteria, and one of some value is
the criterion of _universality_.

Consider, for example, the attraction between the sexes, and ask
whether this represents a native tendency, or whether each individual
acquires it, as he does his "native language", by learning from his
elders. Before the body reaches sexual maturity, there has been
abundant opportunity for the quick-learning child to observe sex
attraction in older people. Yet it is highly improbable that the
liking for the other sex which he begins to show strongly in youth is
simply an acquired taste. It is improbable because the attraction
between the sexes is so universal not only among mankind but among
birds and mammals and, indeed, practically throughout the animal
kingdom.

Fighting is a similar case. Not so universal as the sex instinct, it
still appears almost universally among birds and mammals.

{98}

The human individual is an animal, and some of his native traits are
universal among animals. He is a vertebrate, and some of his traits,
though not present in all animals, are universal among vertebrates. He
is a mammal, with mammalian traits; a primate, with primate traits; a
man with human traits; a Chinaman or Indian or European with racial
traits; belongs to a more or less definite stock or breed within the
race,