ed with fear or is a somewhat different native
tendency, it is certainly a check upon curiosity.

By "contentment" we mean here a liking for the familiar, {157} which
offsets to some extent the fascination of the novel. If you are
perfectly contented, you are not inclined to go out exploring; and
when you have had your fill of the new and strange, you like to get
back to familiar surroundings, where you can rest in content. Just as
playful behavior of all sorts decreases with increasing age, so the
love for exploring decreases, and the elderly person clings to the
familiar. But even children may insist in occupying their own
particular chair, on eating from a particular plate, and on being sung
to sleep always with the same old song. They are "little creatures of
habit", not only in the sense that they readily form habits, but in
the sense that they find satisfaction in familiar ways and things.
Here we see the germ of a "conservative" tendency in human nature,
which balances, to a greater or less extent, and may decidedly
overbalance, the "radical" tendency of exploration.

Laughter.

We certainly must not omit this from our list of instincts, for,
though it does not appear till some time after birth, it has all the
earmarks of an instinctive response. If it were a learned movement, it
could be made at will, whereas, as a matter of fact, few people are
able to produce a convincing laugh except when genuinely amused, which
means when the instinctive tendency to laugh is aroused by some
appropriate stimulus. The emotion that goes with laughing may be
called mirth or amusement, and it is a strongly impulsive state of
mind, the impulse being simply to laugh, with no further end in view.

The most difficult question about laughter is to tell in general
psychological terms what is the stimulus that arouses it. We have
several ingenious theories of humor, which purport to tell; but they
are based on adult humor, and we have as yet no comprehensive genetic
study of laughter, tracing it up from its beginnings in the child.
Laughing certainly belongs with the play instincts, and possibly the
{158} stimulus is no more definite, at first, than that which arouses
other playful activity. The baby seems to smile, at first, just from
good spirits (euphoria). The stimuli that, a little later, arouse a
burst of laughter have an element of what we may call "expected
surprise" (as dropping a rattle and exploding with laughter when i