If only the final results of my experiments with the
dancer and the conclusions to which they lead were
of interest, all of this description of experiments
which served merely to clear the ground and thus make
possible crucial tests might be omitted. It has
seemed to me, however, that the history of the investigation
is valuable, and I am therefore presenting the evolution
of my methods step by step. To be sure, not every
detail of this process can be mentioned, and only a
few of the individual results can be stated, but my
purpose will have been fulfilled if I succeed in showing
how one method of experimentation pointed the way to
another, and how one set of results made possible the
interpretation of others.
As the results of my color vision experiments seemed
to indicate that the red end of the spectrum appears
much darker to the dancer than to us, tests were now
arranged with colors from adjacent regions of the spectrum,
green and blue. The papers used were the Bradley
green and tint No. 1 of the blue. They were not
noticeably different in brightness for the human eye.
Green marked the box to be chosen. Three of the
individuals which had previously been used in the
light blue-orange series, and which therefore had
perfect habits of going to the light blue, were used
for the green-light blue tests. Of these individuals,
No. 1000 became inactive on the fifth day of the experiment,
and the tests with him were discontinued. Twenty
series were given to each of the other mice, with the
results which appear in Table 20. To begin with,
both No. 4 and No. 5 exhibited a preference for the
light blue, as a result of the previous light blue-orange
training. As this preference was gradually destroyed
by the electric shock which was received each time
the light blue box was entered, they seemed utterly
at a loss to know which box to enter. Occasionally
a record of six, seven, or even eight right choices
would be made in a series, but in no case was this
unquestionably due to color discrimination; usually
it could be explained in the light of the order of
the changes in the positions of the cardboards.
For example, series 9, in which No. 5 made a record
of 8 right and 2 wrong, had green on the right for
the first three tests. The animal happened to
choose correctly in the first test, and continued
to do so three times in succession simply because
there was no change in the position of the cardboards.
I have occasionally observed a record of seven right
choices result when it was perfectly evident to the
observer that the mouse could not discriminate visually.
It was to avoid unsafe conclusions and unfair comparisons,
as the result of such misleading series, that three
perfect series in succession were required as evidence
of a perfectly formed habit of discrimination.
TABLE 20
GREEN-LIGHT BLUE TESTS
Date
No. 1000 No. 4 No. 5
SERIES 1906 RIGHT WRONG RIGHT WRONG
RIGHT WRONG
(GREEN)
(BLUE) (GREEN) (BLUE) (GREEN) (BLUE)
Copyrights
The Dancing Mouse from Project Gutenberg. Public domain.
