would be no
wrangling of opposing interests; it would be possible to find out
whether the permitted limit were overstepped or not with an
exactitude similar to that with which the weight or the chemical
constitution of a trade commodity is examined. Certainly the
experiment establishes here conditions which are very different from
those of practical life. The customer who wants to buy a particular
picture postal card which he saw once before and to whom the salesman
offers a similar one, suggesting that it is the same, is facing only
one card and not a group of six. But in practical life the card which
be has seen was not observed with the definite intention of keeping
the memory picture in mind, and months may have passed since it was
seen. The memory picture which the customer has in his consciousness
when he seeks the particular card is much weakened by this
circumstance too. We secure this weakening artificially by the
arrangement of the experiment in placing the card in a group of six or
ten and exposing them for a few seconds only. The force of attention
and the corresponding memory-value are by this distribution diminished
in a definite degree in the case of every single card.

The investigation must include a careful study of the size of the
groups, of the time-relations, of the percentage of correct answers,
all under the point of view of greatest fitness for practical
application. In the Harvard laboratory the research has been carried
on partly with such picture material, partly with word material, and
partly with concrete objects.[54] Whatever the details of the outcome
may be, we hope that the work will lead to results which may, indeed,
make such a psychotechnical use possible. Its principles and formulae
might easily be adjusted to any marketable material. As a matter of
course, if in future the courts were ever to accept such
psychological, experimental methods, it would be intolerable
dilettantism if such experiments were carried on by lawyers and
district attorneys. It is as true of this economic legal question as
of many other legal psychological problems that its introduction into
the courtroom can become desirable only when psychological experts are
engaged and called in the same way as chemical or medical experts are
invited to the court. On the other hand, there is surely not the
slightest desire on the part of psychologists to be dragged into
humiliating performances like those which not only h