Reversing Hands Of Clock
PROCEDURE. Say to the subject: "_Suppose it is six twenty-two o'clock,
that is, twenty-two minutes after six; can you see in your mind where
the large hand would be, and where the small hand would be?_" Subjects
of 12- to 14-year intelligence practically always answer this in the
affirmative. Then continue: "_Now, suppose the two hands of the clock
were to trade places, so that the large hand takes the place where the
mall hand was, and the small hand takes the place where the large hand
was. What time would it then be?_"
Repeat the test with the hands at 8.10 (10 minutes after 8), and again
with the hands at 2.46 (14 minutes before 3).
The subject is not allowed to look at a clock or watch, or to aid
himself by drawing, but must work out the problem mentally. As a rule
the answer is given within a few seconds or not at all. If an answer is
not forthcoming within two minutes the score is failure.
SCORING. The test is passed if _two of the three_ problems are solved
within the following range of accuracy: the first solution is considered
correct if the answer falls between 4.30 and 4.35, inclusive; the second
if the answer falls between 1.40 and 1.45, and the third if the answer
falls between 9.10 and 9.15.
REMARKS. It appears that success in the test chiefly depends upon
voluntary control over constructive visual imagery. Weakness of visual
imagery may account for the failure of a considerable percentage of
adults to pass the test. Visual imagery, however, is not absolutely
necessary to success. One 8-year-old prodigy, who had 12-year
intelligence, arrived in forty seconds at a strictly mathematical
solution for the second problem, as follows: "If it is 2.46, and the
hands trade places, then the little hand has gone about one fourth of
the distance from 9 o'clock to 10 o'clock. One fourth of 60 minutes is
15 minutes, and so the time would be 15 minutes after 9 o'clock." Such a
solution is certainly possible by the use of verbal imagery of any type.
The test shows a high correlation with mental age, but more than most
others it is subject to the influence of cribbing. For this reason,
other positions of the clock hands should be tried out for the purpose
of finding substitute experiments of equal difficulty. Until such
experiments have been made, it will be necessary to confine the
experiment to the three positions here presented.
Schooling seems to have no influence whatever on the percentage of
This test was first used by Binet in 1905, but was not included in
either the 1908 or 1911 series. Goddard and Kuhlmann both include the
test in their revisions, placing it in year XV. They give only two
problems (our _a_ and _c_) and require that both be answered correctly.
Neither Goddard nor Kuhlmann, however, indicates the degree of error
Something depends upon original position of the hands. Binet used 6.20
and 2.46. For some reason the 2.46 arrangement is much more difficult
than either 8.10 or 6.22, yielding almost twice as many failures as
either of the other positions.