The nervous system of a fresh and highly-fed horse sends its
order to the motory system so quickly, that no time is allowed
for him to consider whether or not the danger is real.
After one violent start, when he is excited and the blood
flows freely through his brain, he is very apt to start again;
and so it is, as I have noticed, with young infants.
A start from a sudden noise, when the stimulus is conveyed through the
auditory nerves, is always accompanied in grown-up persons by the winking
of the eyelids.[13] I observed, however, that though my infants started
at sudden sounds, when under a fortnight old, they certainly did not always
wink their eyes, and I believe never did so. The start of an older infant
apparently represents a vague catching hold of something to prevent falling.
I shook a pasteboard box close before the eyes of one of my infants, when 114
days old, and it did not in the least wink; but when I put a few comfits
into the box, holding it in the same position as before, and rattled them,
the child blinked its eyes violently every time, and started a little.
It was obviously impossible that a carefully-guarded infant could have learnt
by experience that a rattling sound near its eyes indicated danger to them.
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