We have named the experiment an "induction test." It might be supposed that the solution would ordinarily be arrived at by deduction, or by an _a-priori_ logical analysis of the principle involved. This, however, is rarely the case. Not one average adult out of ten reasons out the situation in this purely logical manner. It is ordinarily only after one or more mistakes have been made and have been exposed by the examiner holding up the unfolded paper to view that the correct principle is grasped. In the absence of deductive reasoning the subject must note that each unfolded sheet contains twice as many holes as the previous one, and must infer that folding the paper again will again double the number. The ability tested is the ability to generalize from particulars where the common element of the particulars can be discerned only by the selective action of attention, in this case attention to the fact that each number is the double of its predecessor. XIV, 3. GIVING DIFFERENCES BETWEEN A PRESIDENT AND A KING PROCEDURE. Say: "_There are three main differences between a president and a king; what are they?_" If the subject stops after one difference is given, we urge him on, if possible, until three are given. SCORING. The three differences relate to power, tenure, and manner of accession. Only these differences are considered correct, and the successful response must include at least two of the three. We disregard crudities of expression and note merely whether the subject has the essential idea. As regards power, for example, any of the following responses are satisfactory: "The king is absolute and the president is not." "The king rules by himself, but the president rules with the help of the people." "Kings can have things their own way more than presidents can," etc. It may be objected that the reverse of this is sometimes true, that the king of to-day often has less power than the average president. Sometimes subjects mention this fact, and when they do we credit them with this part of the test. As a matter of fact, however, this answer is seldom given. Sometimes the subject does not stop until he has given a half-dozen or more differences, and in such cases the first three differences may be trivial and some of the later ones essential. The question then arises whether we should disregard the errors and pass the subject on his later correct responses. The rule in such cases is to ask the subject to pick out the "three main differences." Sometimes accession and tenure are given in the form of a single contrast, as: "The president is elected, but the king inherits his throne and rules for life." This answer entitles the subject to credit for both accession and tenure, the contrast as regards tenure being plainly implied. Unsatisfactory contrasts are of many kinds and are often amusing. Some of the most common are the following:--