ligence from his
photograph. This has now been pretty well established. Photographs of
persons of various degrees of intelligence are placed before those who
are reputed to be good judges, and their estimates compared with the
test ratings, and there is no correspondence. You might just as well
look at the back of the photograph as at the front.

Even with the person before you, you are likely to commit great
errors. This sort of incident has happened. A young woman is brought
before the court for delinquency, and the psychologist who has tested
her testifies that she is of low intelligence. But the young woman is
good-looking and graceful in her speech and manners, and so impresses
the judge that he dismisses as "absurd" the notion of her being
feeble-minded. He sets her free, on which she promptly gets into
trouble again. Apparently the only way to perceive intelligence is to
see a person in action, preferably under standard conditions, where
his performance can be measured; that is to say, in an intelligence
test.

Errors of Perception

The grocer needs to be assured of the accuracy of his scales, and the
chemist of the high accuracy of his chemical balance; the surveyor
needs to know about the errors that may creep into the process of
measuring the length of a line or angle. All of them, using
instruments to assist in accurate perception of facts, are concerned
about the accuracy of their instruments. Now, we all use the senses in
perceiving facts, and "errors of sense" therefore concern us {447}
all. Some of the errors committed in sense perception can be laid at
the door of the senses, and some rather belong in the sphere of
perception proper.

If you come out of a cold room into a warm room, the latter seems
warmer than it is; and if you come out of a dark room into a light
room, the latter seems brighter than it is. These errors, due to
adaptation of the temperature sense and of the retina, are properly
classed as errors of sense.

If you are taking a child's temperature with a "minute thermometer",
it is best to use your watch to tell you when the minute is up, for
the minute, when you are simply waiting for it to pass, seems very
long. But if you are "working against time", a minute seems short. The
professor is shocked when the closing bell rings, and thinks that
certainly the hour cannot be up; but some of the students have been
consulting their watches for quite a long while, being sure the hour
m