ethod of getting reaction times
has been in use for a number of years, especially by the astronomers
who need to know, in making their observations, how much time is taken
by the observer in recording a transit or other observation. It is
part of the astronomer's "personal equation."

Proceeding with this "simple-reaction" experiment as a basis, the
psychologists have varied the instructions to the subject so as to
secure from him the different times which he takes for more
complicated mental processes, such as distinguishing between two or
more impressions, counting, multiplying, dividing, etc., before
reacting; or they have him wait for an associated idea to come up
before giving his response, with many other variations. By comparing
these different times among themselves, interesting results are
reached concerning the mental processes involved and also about the
differences of different individuals in the simpler operations of
their daily lives. The following research carried out by Mr. B.[4]
serves to illustrate both of these assertions.

[Footnote 4: The writer.]

Mr. B. wished to inquire further into a fact found out by several
persons by this method: the fact that there is an important difference
in the length of a person's reaction time according to the direction
of his attention during the experiment. If, for example, Mr. X. be
tested, it is possible that he may prefer to attend strictly to the
signal, letting his finger push the key without direct care and
supervision. If this be true, and we then interfere with his way of
proceeding, by telling him that he must attend to his finger, and
allow the signal to take care of itself, we find that he has great
difficulty in doing so, grows embarrassed, and his reaction time
becomes very irregular and much longer. Yet another person, say Y, may
show just the opposite state of things; he finds it easier to pay
attention to his hand, and when he does so he gets shorter and also
more regular times than when he attends to the signal-sound.

It occurred to Mr. B. that the striking differences given by different
persons in this matter of the most favourable direction of the
attention might be connected with the facts brought out by the
physiological psychologists in connection with speech; namely, that
one person is a "visual," in speaking, using mainly sight images of
words, while another is a "motor," using mainly muscular images, and
yet another an "auditive," using