tures of a real jury deliberation which have
nothing to do with the mental action itself. Moreover, it is evident
that the situations to be judged must allow a definite knowledge as to
the objective truth. The experimenter must know which verdict of his
voters corresponds to the real facts. Secondly, the situation must be
difficult in order that a real doubt may prevail. If all the voters
were on one side from the start, no discussion would be needed.
Thirdly, it must be a rather complex situation in order that the
judgment may be influenced by a number of motives. Only in this case
will it be possible for the discussion to point out factors which the
other party may have overlooked, thus giving a chance for changes of
mind. All these demands must be fulfilled if the experiment is really
to picture the jury function. But it would be utterly superfluous and
would make the exact measurement impossible if the material on which
the judgment is to be based were of the same kind of which the
evidence in the courtroom is composed. The trial by jury in an actual
criminal case may involve many picturesque and interesting details,
but the mental act of judging is no different when the most trivial
objects are chosen.

I settled on the following simple device: I used sheets of dark gray
cardboard. On each were pasted white paper dots of different form and
in an irregular order. Each card had between ninety-two and a hundred
and eight such white dots of different sizes. The task was to compare
the number of spots on one card with the number of spots on another.
Perhaps I held up a card with a hundred and four dots above, and below
one with ninety-eight. Then the subjects of the experiment had to
decide whether the upper card had more dots or fewer dots or an equal
number compared with the lower one. I made the first set of
experiments with eighteen Harvard students. I took more than the
twelve men who form a jury in order to reenforce the possible effect,
but did not wish to exceed the number greatly, so that the character
of the discussion might be similar to that in a jury. A much larger
number would have made the discussion too formal or too unruly. The
eighteen men sat around a long table and were first allowed to look
for half a minute at the two big cards, each forming his judgment
independently. Then at a signal every one had to write down whether
the number of dots on the upper card was larger, equal, or smaller.
Immediate