has ever thrown stones should
have the data for such an approximate solution. Not a day of schooling
is necessary.

(b) _Problem as to the weight of a fish in water_

PROCEDURE. Say to the subject: "_You know, of course, that water holds
up a fish that is placed in it. Well, here is a problem. Suppose we have
a bucket which is partly full of water. We place the bucket on the
scales and find that with the water in it it weighs exactly 45 pounds.
Then we put a 5-pound fish into the bucket of water. Now, what will the
whole thing weigh?_"

SCORING. Many subjects even as low as 9- or 10-year intelligence will
answer promptly, "Why, 45 pounds and 5 pounds makes 50 pounds, of
course." But this is not sufficient. We proceed to ask, with serious
demeanor: "_How can this be correct, since the water itself holds up the
fish?_" The young subject who has answered so glibly now laughs
sheepishly and apologizes for his error, saying that he answered without
thinking, etc. This response is scored failure without further
questioning.

Other subjects, mostly above the 14-year level, adhere to the answer
"50 pounds," however strongly we urge the argument about the water
holding up the fish. In response to our question, "_How can that be the
case?_" it is sufficient if the subject replies that "The weight is
there just the same; the scales have to hold up the bucket and the
bucket has to hold up the water," or words to that effect. Only some
such response as this is satisfactory. If the subject keeps changing his
answer or says that he _thinks_ the weight would be 50 pounds, but is
not certain, the score is failure.

(c) _Difficulty of hitting a distant mark_

PROCEDURE. Say to the subject: "_You know, do you not, what it means
when they say a gun 'carries 100 yards'? It means that the bullet goes
that far before it drops to amount to anything._" All boys and most
girls more than a dozen years old understand this readily. If the
subject does not understand, we explain again what it means for a gun
"to carry" a given distance. When this part is clear, we proceed as
follows: "_Now, suppose a man is shooting at a mark about the size of a
quart can. His rifle carries perfectly more than 100 yards. With such a
gun is it any harder to hit the mark at 100 yards than it is at
50 yards?_" After the response is given, we ask the subject to explain.

SCORING. Simply to say that it would be easier at 50 yards is not
sufficient, nor can w