4. "At first, the baby very likely perceives a ball simply as something for him to handle and throw; but, through the medium of blocked response, he comes to perceive it more objectively, i.e., as an object related to other objects, and not simply related to himself." Explain and ill.u.s.trate this statement.

5. Give an example from the field of auditory perceptions where "isolation" is very much in evidence.

6. Can you see any law a.n.a.logous to Weber's law in the field of financial profit and loss? Does a dollar gained or lost _seem_ the same amount, without regard to the total amount possessed?

7. Trial and error perception. Go about the room with closed eyes, and identify objects by touching them with the hands. Notice whether your first impression gives place to corrected impressions.

8. Perception of form by "active" and "pa.s.sive" touch. With the eyes closed, try to distinguish objects of different shapes (a) by letting them simply rest upon the skin, and (b) by handling them. What senses cooperate in furnishing data for "active touch"?

9. Binocular parallax, or the differing views of the same solid object obtained by the two eyes. Hold a small, three-dimensional object a foot in front of the face, and notice carefully the view of it obtained by each eye separately. A pencil, pointing towards the face, gives very different views. What becomes of the two monocular views when both eyes are open at once?

10. Binocular compared with monocular perception of "depth"

or distance away. Take a pencil in each hand, and bring the points together a foot in front of the face, while only one eye is open.

When the points seem to be nearly touching, open the other eye, and see whether the two points still seem to be close together.

Repeat.

REFERENCES

Discussions of perception that are in some respects fuller than the present chapter can be found in C. H. Judd's _Psychology, General Introduction_, 2nd edition, 1917, pp. 162-194; in t.i.tchener's _Textbook of Psychology_, 1909, pp. 303-373; and in Warren's _Human Psychology_, 1919, pp. 232-269.

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CHAPTER XVIII

REASONING

THE PROCESS OF MENTAL, AS DISTINGUISHED FROM MOTOR EXPLORATION

We are still on the general topic of "discovery". Indeed, we are still on the topic of perception; we come now to that form of perception which is different from sense perception. The reasoner is an explorer, and the culmination of his explorations is the perception of some fact previously unknown to him.

Reasoning might be described as mental exploration, and distinguished from purely motor exploration of the trial and error variety. Suppose you need the hammer, and go to the place where it is kept, only to find it gone. Now if you simply proceed to look here and there, ransacking the house without any plan, that would be motor exploration. But if, finding this trial and error procedure to be laborious and almost hopeless, you sit down and think, "Where can that hammer be? Probably where I used it last!" you may recall using it for a certain purpose, in a certain place, go there and find it. You have subst.i.tuted mental exploration of the situation for purely motor exploration, and saved time and effort. Such instances show the use of reasoning, and the part it plays in behavior.

The _process_ of reasoning is also ill.u.s.trated very well in these simple cases. It is an exploratory process, a searching for facts. In a way, it is a trial and error process. If you don't ransack the house, at least you ransack your memory, in search for facts that will a.s.sist you. You recall this fact {463} and that, you turn this way and that, mentally, till some fact is recalled that serves your need. No more in reasoning than in motor exploration can you hope to go straight to the desired goal.

Animal and Human Exploration

Is man the only reasoning animal? The experimental work on animal learning, reviewed in one of our earlier chapters, was begun with this question in mind. Previous evidence on this point had been limited to anecdotes, such as that of the dog that was found opening a gate by lifting the latch with his nose, and was supposed to have seen men open the gate in this way, and to have _reasoned_ that if a man could do that, why not a dog? The objection to this sort of evidence is that the dog's manner of acquiring the trick was not observed. Perhaps he reasoned it out, and perhaps he got it by accident--you cannot tell without watching the process of learning. You must experiment, by taking a dog that does not know the trick, and perhaps first "showing him" how to open the gate by lifting the latch; but it was found that dogs and cats, and even monkeys, could not learn the trick in this way. If, however, you placed a dog in a cage, the door of which could be opened by lifting a latch, and motivated the dog strongly by having him hungry and placing food just outside, then the dog went to work by trial and error, and lifted the latch in the course of his varied reactions; and if he were placed back in the cage time after time, his unsuccessful reactions were gradually eliminated and the successful reaction was firmly attached to the situation of being in that cage, so that he would finally lift the latch without any hesitation.

The behavior of the animal does not look like reasoning. For one thing, it is too impulsive and motor. The typical {464} att.i.tudes of the reasoner, whether "lost in thought" or "studying over things", do not appear in the dog, or even in the monkey, though traces of them may perhaps be seen in the chimpanzee and other manlike apes. Further, the animal's learning curve fails to show sudden improvements such as in human learning curves follow "seeing into" the problem. In short, there is nothing to indicate that the animal recalls facts previously observed or sees their bearing on the problem in hand. He works by motor exploration, instead of mental. He does not search for "considerations" that may furnish a clue.

The behavior of human beings, placed figuratively in a cage, sometimes differs very little from that of an animal. Certainly it shows plenty of trial and error and random motor exploration; and often the puzzle is so blind that nothing but motor exploration will bring the solution. What the human behavior does show that is mostly absent from the animal is (1) attentive studying over the problem, scrutinizing it on various sides, in the effort to find a clue; (2) thinking, typically with closed eyes or abstracted gaze, in the effort to recall something that may bear on the problem; and (3) sudden "insights" when the present problem is seen in the light of past experience.

Though reason differs from animal trial and error in these respects, it still is a tentative, try-and-try-again process. The right clue is not necessarily hit upon at the first try; usually the reasoner finds one clue after another, and follows each one up by recall, only to get nowhere, till finally he notices a sign that recalls a pertinent meaning. His exploration of the situation, though carried on by aid of recalled experience instead of by locomotion, still resembles finding the way out of a maze with many blind alleys. In short, reasoning may be called a trial and error process in the sphere of mental reactions.

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The reader familiar with geometry, which is distinctly a reasoning science, can readily verify this description. It is true that the demonstrations are set down in the book in a thoroughly orderly manner, proceeding straight from the given a.s.sumption to the final conclusion; but such a demonstration is only a dried specimen and does not by any means picture the living mental process of reasoning out a proposition. Solving an "original" is far from a straight-forward process. You begin with a situation (what is "given") involving a problem (what is to be proved), and, studying over this lay-out you notice a certain fact which looks like a clue; this recalls some previous proposition which gives the significance of the clue, but often turns out to have no bearing on the problem, so that you shift to another clue; and so on, by what is certainly a trial and error process, till some fact noted in the situation plus some knowledge recalled by this fact, taken together, reveal the truth of the proposition.

Reasoning Culminates in Inference

When you have described reasoning as a process of mental exploration, you have told only half the story. The successful reasoner not only seeks, but finds. He not only ransacks his memory for data bearing on his problem, but he finally "sees" the solution clearly. The whole exploratory process culminates in a perceptive reaction. What he "sees" is not presented to his senses at the moment, but he "sees that something _must_ be so". This kind of perception may be called _inference_.

To bring out distinctly the perceptive reaction in reasoning, let us cite a few very simple cases. Two freshmen in college, getting acquainted, ask about each other's fathers and find that both are alumni of this same college. "What cla.s.s was your father in?" "In the cla.s.s of 1900. And {466} yours?" "Why, he was in 1900, too. Our fathers were in the same cla.s.s; they must know each other!" Here two facts, one contributed by one person and the other by another person, enable both to perceive a third fact which neither of them knew before. Inference, typically, is a response to two facts, and the response consists in perceiving a third fact that is bound up in the other two.

You do not infer what you can perceive directly by the senses. If Mary and Kate are standing side by side, you can _see_ which is the taller.

But if they are not side by side, but Mary's height is given as so much and Kate's as an inch more, then from these two facts you know, by inference, that Kate is taller than Mary.

"Have we set the table for the right number of people?" "Well, we can see when the party comes to the table." "Oh! but we can tell now by counting. How many are there to be seated? One, two, three--fifteen in all. Now count the places at table--only fourteen. You will have to make room for one more." This reducing of the problem to numbers and then seeing how the numbers compare is one very simple and useful kind of inference.

Indirect comparison may be accomplished by other similar devices. I can reach around this tree trunk, but not around that, and thus I perceive that the second tree is thicker than the first, even though it may not look so. If two things are each found to be equal to a third thing, then I see they must be equal to each other; if one is larger than my yardstick and the other smaller, then I see they must be unequal.

Of the two facts which, taken together, yield an inferred fact, one is often a general rule or principle, and the inference then consists in seeing how the general rule applies to a special case. A dealer offers you a fine-looking diamond ring for five dollars, but you recall the rule that "all genuine diamonds are expensive", and perceive that this {467} diamond must be an imitation. This also is an instance of indirect comparison, the yardstick being the sum of five dollars; this ring measures five dollars, but any genuine diamond measures more than five dollars, and therefore a discrepancy is visible between this diamond and a genuine diamond. You can't see the discrepancy by the eye, but you see it by way of indirect comparison, just as you discover the difference between the heights of Mary and Kate by aid of the yardstick.

If all French writers are clear, then Binet, a French writer, must be clear. Here "French writers" furnish your yardstick. Perhaps it would suit this case a little better if, instead of speaking of indirect comparison by aid of a mental yardstick, we spoke in terms of "relations". When you have before your mind the relation of A to M, and also the relation of B to M, you may be able to see, or infer, a relation between A and B. M is the common point of reference to which A and B are related. Binet stands in a certain relation to "French writers", who furnish the point of reference; that is, he is one of them. Clear writing stands in a certain relation to French writers, being one of their qualities; from which combination of relations we perceive clear writing as a quality of Binet.

Just as an illusion is a false sense perception, so a false inference is called a "fallacy". One great cause of fallacies consists in the confused way in which facts are sometimes presented, resulting in failure to see the relationships clearly. If you read that

"Smith is taller than Brown; and Jones is shorter than Smith; and therefore Jones is shorter than Brown,"

the mix-up of "taller" and "shorter" makes it difficult to get the relationships clearly before you, and you are likely {468} to make a mistake. Or again, if Mary and Jane both resemble Winifred, can you infer that they resemble each other? You are likely to think so at first, till you notice that resemblance is not a precise enough relation to serve for purposes of indirect comparison. Mary may resemble Winifred in one respect, and Jane may resemble her in another respect, and there may be no resemblance between Mary and Jane.

Or, again,

"All French writers are clear; but James was not a French writer; and therefore James was not a clear writer,"

may cause some confusion from failure to notice that the relation between French writers and clear writing is not reversible so that we could turn about and a.s.sert that all clear writers were French.

The reasoner needs a clear head and a steady mental eye; he needs to look squarely and steadily at his two given statements in order to perceive their exact relationship. Diagrams and symbols often a.s.sist in keeping the essential facts clear of extraneous matter, and so facilitate the right response.

To sum up: the process of reasoning culminates in two facts being present as stimuli, and the response, called "inference", consists in perceiving a third fact that is implicated in the two stimulus-facts.

It is a good case of the law of combination, and at the same time it is a case where "isolation" is needed, otherwise the response will be partly aroused by irrelevant stimuli, and thus be liable to error.

Varieties of Reasoning

Reasoning as a whole is a process of mental exploration culminating in inference. Now, without regard to possible {469} variations of the perceptive response of inference, there are at least different varieties of the exploratory process leading up to inference. The situation that arouses reasoning differs from one case to another, the motive for engaging in this rather laborious mental process differs, and the order of events in the process differs. There are several main types of reasoning, considered as a process of mental exploration.

1. Reasoning out the solution of a practical problem.

A "problem" is a situation for which we have no ready and successful response. We cannot successfully respond by instinct or by previously acquired habit. We must _find out_ what to do. We explore the situation, partly by the senses and actual movement, partly by the use of our wits. We observe facts in the situation that recall previous experiences or previously learned rules and principles, and apply these to the present case. Many of these clues we reject at once as of no use; others we may try out and find useless; some we may think through and thus find useless; but finally, if our exploration is successful, we observe a real clue, recall a pertinent guiding principle, and see the way out of our problem.

Two boys went into the woods for a day's outing. They climbed about all the morning, and ate their lunch in a little clearing by the side of a brook. Then they started for home, striking straight through the woods, as they thought, in the direction of home. After quite a long tramp, when they thought they should be about out of the woods, they saw clear s.p.a.ce ahead, and, pushing forward eagerly, found themselves in the same little clearing where they had eaten their lunch!

Reasoning process No. 1 now occurred: one of the boys _recalled_ that when traversing the woods without any compa.s.s or landmark, the traveller is very likely to go in a circle; inference, "That is what we have done and {470} we probably shall do the same thing again if we go ahead. We may as well sit down and think it over."