wn, above and
below, before and behind, etc., and arrives at a knowledge of right and
left rather tardily.

How may we explain the late distinction of right and left as compared
with up and down? At least four theories may be advanced: (1) Something
depends on the frequency with which children have occasion to make the
respective distinctions. (2) It may be explained on the supposition that
kinaesthetic sensations are more prominently involved in distinctions of
up and down than in distinctions of right and left. It is certainly true
that, in distinguishing the two sides of a thing, less bodily movement
is ordinarily required than in distinctions of its upper and lower
aspects. The former demands only a shift of the eyes, the latter often
requires an upward or downward movement of the head. (3) It may be due
to the fact that the appearance of an object is more affected by
differences in vertical orientation than by those of horizontal
orientation. We see an object now from one side, now from the other, and
the two aspects easily blend, while the two aspects corresponding to
above and below are not viewed in such rapid succession and so remain
much more distinct from one another in the child's mind. Or, (4), the
difference may be mainly a matter of language. The child undoubtedly
hears the words _up_ and _down_ much oftener than _right_ and _left_,
and thus learns their meaning earlier. Horizontal distinctions are
commonly made in such terms as _this side_ and _that side_, or merely by
pointing, while in the case of vertical distinctions the words _up_ and
_down_ are used constantly. This last explanation is a very plausible
one, but it is very probable that other factors are also involved.

The distinction between right and left has a certain inherent and more
or less mysterious difficulty. To convince one's self of this it is only
necessary to try a little experiment on the first fifty persons one
chances to meet. The experiment is as follows. Say: "I am going to ask
you a question and I want you to answer it as quickly as you can." Then
ask: "Which is your right hand?" About forty persons out of fifty will
answer correctly without a second's hesitation, several will require two
or three seconds to respond, while a few, possibly four or five
per cent, will grow confused and perhaps be unable to respond for five
or ten seconds. Some very intelligent adults cannot possibly tell which
is the right or left hand without fi