The Science of Human Nature | Page 7

Let us illustrate psychological method
by a typical experiment. Suppose we wish to measure the individual
differences among the members of a class with respect to a certain
ability; namely, the muscular speed of the right hand. Psychological
laboratories have delicate apparatus for making such a study. But let us
see how we can do it, roughly at least, without any apparatus. Let each
member of the class take a sheet of paper and a pencil, and make as
many strokes as possible in a half-minute, as shown in Figure I. The
instructor can keep the time with a stop watch, or less accurately with
the second hand of an ordinary watch. Before beginning the experiment,
the instructor should have each student taking the test try it for a second
or two. This is to make sure that all understand what they are to do.
When the instructor is sure that all understand, he should have the
students hold their pencils in readiness above the paper, and at the
signal, "Begin," all should start at the same time and make as many
marks as possible in the half-minute. The strokes can then be counted
and the individual scores recorded. The experiment should be repeated
several times, say six or eight, and the average score for each individual
recorded.
[Illustration: FIGURE I.--STROKES MADE IN THIRTY SECONDS
A test of muscular speed]
Whether the result in such a performance as this varies from day to day,
and is accidental, or whether it is constant and fundamental, can be

determined by repeating the experiment from day to day. This
repetition will also show whether improvement comes from practice.
If it is decided to repeat the experiment in order to study these factors,
constancy and the effects of practice, some method of studying and
interpreting the results must be found. Elaborate methods of doing this
are known to psychologists, but the beginner must use a simpler
method. When the experiment is performed for the first time, the
students can be ranked with reference to their abilities, the fastest one
being called "first," the second highest, "second," and so on down to
the slowest performer. Then after the experiment has been performed
the second time, the students can be again ranked.
A rough comparison can then be made as follows: Determine how
many who were in the best half in the first experiment are among the
best half in the second experiment. If most who were among the best
half the first time are among the best half in the second experiment,
constancy in this performance is indicated. Or we might determine how
many change their ranks and how much they change. Suppose there are
thirty in the class and only four improve their ranks and these to the
extent of only two places each. This would indicate a high degree of
constancy. Two different performances can be compared as above
described. The abilities on successive days can be determined by taking
the average rank of the first day and comparing it with the average rank
of the second day.
If the effects of practice are to be studied, the experiments must be kept
up for many days, and each student's work on the first day compared
with his work on succeeding days. Then a graph can be plotted to show
the improvement from day to day. The average daily speed of the class
can be taken and a graph made to show the improvement of the class as
a whole. This might be plotted in black ink, then each individual
student could put on his improvement in red ink, for comparison. A
group of thirty may be considered as furnishing a fair average or norm
in this kind of performance.
In connection with this simple performance, making marks as fast as
possible, it is evident that many problems arise. It would take several

months to solve anything like all of them. It might be interesting, for
example, to determine whether one's speed in writing is related to this
simple speed in marking. Each member of the class might submit a
plan for making such a study.
The foregoing simple study illustrates the procedure of psychology in
all experimentation. A psychological experiment is an attempt to find
out the truth in regard to some aspect of human nature. In finding out
this truth, we must throw about the experiment all possible safeguards.
Every source of error must be discovered and eliminated. In the above
experiment, for example, the work must be done at the same time of
day, or else we must prove that doing it at different times of day makes
no difference. Nothing must be taken for granted, and nothing must be
assumed. Psychology, then, is like all the other sciences, in that its
method