Sixteen Experimental Investigations from the Harvard Psychological Laboratory by Hugo Münsterberg (100 books to read .txt) 📕

felt both contacts I took two brass rods about four inches long,

sharpened one end and rounded off the other. The subject sat with the

palm of his right hand on the back of his left and his fingers

interlaced. I stimulated the back of his fingers on the second

phalanges with the sharp end of one rod and the blunt end of the other

and asked him to tell whether the sharp point was to the right or to

the left of the other. I will not give the results in detail here, but

only wish to mention a few things for the purpose of illustrating the

point in question. Many of the answers were wrong. Frequently the

subject would say both were on the same finger, when really they were

on fingers of opposite hands, which, however, in this position were

adjacent fingers. Sometimes when this happened I would ask him which

finger they were on, and after he had answered I would leave the point

on the finger on which he said both points were and move the other

point over to the same finger, then move it back to its original

position, then again over to the finger on which the other point was

resting, and so on, several times. The subject would tell me that I

was raising one point and putting it down again in the same place all

of the time. Often a subject would tell me he felt both points on the

same finger, but that he could not tell to which hand the finger

belonged. When two or more fingers intervened between the fingers

touched no subject ever had any difficulty in telling which was the

sharp and which the blunt point, but when adjacent fingers were

touched it was very common for the subject to say he could not tell

which was which. This cannot be because there is more difference in

the quality of the contacts in one case than in the other. If they

were on the same finger it might be said that they were stimulating

the same general area, but since one is on one hand and one on the

other this is impossible. The subject does not think the two points

are in the same place, because he feels two qualities and hence he

infers two things, and he knows two things cannot be in the same place

at the same time. If the two contacts were of the same quality

probably they would be perceived as one on account of the absence of

difference, for the absence of difference is precisely the quality of

oneness.

These facts, together with those mentioned before, seem to me to

indicate that errors of localization are largely responsible for

judgments which seem to be due to fusion or diffusion of sensations.

But they are responsible only in this way, they prevent the correction

of the first impression. I do not mean that a person never changes his

judgment after having once made it, but a change of judgment is not

necessarily a correction. Often it is just the contrary. But where a

wrong judgment is made and cannot be corrected inability to localize

is a prominent factor. This, however, is only a secondary factor in

the perception of number. The cardinal point seems to me the

following:

Any touch sensation, no matter by how many objects it is produced, is

one, and number is an inference based on a temporal series of

sensations. It may be that we can learn by association to infer number

immediately from the quality of a sensation, but that means only that

we recognize the sensation as one we have had before and have found it

convenient to separate into parts and regard one part after the other,

and we remember into how many parts we separated it. This separating

into parts is a time process. What we shall regard as one is a mere

matter of convenience. Continuity sometimes affords a convenient basis

for unity and sometimes it does not. There is no standard of oneness

in the objective world. We separate things as far as convenience or

time permits and then stop and call that one which our own attitude

has determined shall be one.

That we do associate a sensation with whatever idea we have previously

connected it with, even though that idea be that of the number of

objects producing it, is clearly shown by some experiments which I

performed in the laboratory of Columbia University. I took three

little round pieces of wood and set them in the form of a triangle. I

asked the subject to pass his right hand through a screen and told him

I wanted to train him to perceive one, two, three and four contacts at

a time on the back of his hand, and that I would tell him always how

many I gave him until he learned to do it. When it came to three I

gave him two points near the knuckles and one toward the wrist and

told him that was three. Then I turned the instrument around and gave

him one point near the knuckles and two toward the wrist and told him

that was four. As soon as he was sure he distinguished all of the

points I stopped telling him and asked him to answer the number. I had

four subjects, and each one learned very soon to recognize the four

contacts when three were given in the manner mentioned above. I then

repeated the same thing on the left hand, except that I did not tell

him anything, but merely asked him to answer the number of contacts he

felt. In every case the idea of four was so firmly associated with

that particular kind of a sensation that it was still called four when

given on the hand which had not been trained. I gave each subject a

diagram of his hand and asked him to indicate the position of the

points when three were given and when four were given. This was done

without difficulty. Two subjects said they perceived the four contacts

more distinctly than the three, and two said they perceived the three

more distinctly than the four.

It seems very evident that the sensation produced by three contacts is

no more complex when interpreted as four than when interpreted as

three. If that is true, then it must also be evident that the

sensation produced by one contact is no more complex when interpreted

as two than when interpreted as one. The converse should also be true,

that the sensation produced by two contacts is no less complex when

interpreted as one than when interpreted as two. Difference in number

does not indicate difference in complexity. The sensation of four is

not made up of four sensations of one. It is a unit as much as the

sensation of one is.

There remains but one point to be elaborated. If number is not a

quality of objects, but is merely a matter of attitude of the subject,

we should not expect to find a very clear-cut line of demarcation

between the different numbers except with regard to those things which

we constantly consider in terms of number. Some of our associations

are so firmly established and so uniform that we are likely to regard

them as necessary. It is not so with our associations of number and

touch sensations. We have there only a vague, general notion of what

the sensation of one or two is, because usually it does not make much

difference to us, yet some sensations are so well established in our

minds that we call them one, two or four as the case may be without

hesitation. Other sensations are not so, and it is difficult to tell

to which class they belong. Just so it is easy to tell a pure yellow

color from a pure orange, yet they shade into each other, so that it

is impossible to tell where one leaves off and the other begins. If we

could speak of a one-two sensation as we speak of a yellow-orange

color we might be better able to describe our sensations. It would,

indeed, be convenient if we could call a sensation which seems like

one with a suggestion of two about it a two-one sensation, and one

that seems nearly like two but yet suggests one a one-two sensation.

Since we cannot do this, we must do the best we can and describe a

sensation in terms of the number it most strongly suggests. Subjects

very often, as has been mentioned before, describe a sensation as

‘more than one but less than two,’ but when pressed for an answer will

say whichever number it most resembles. A person would do the same

thing if he were shown spectral colors from orange to yellow and told

to name each one either orange or yellow. At one end he would be sure

to say orange and at the other yellow, but in the middle of the series

his answers would likely depend upon the order in which the colors

were shown, just as in determining the threshold for the perception of

two points by the method of minimal changes the answers in the

ascending series are not the same as those in the descending series.

The experiments have shown that the sensation produced by two points,

even when they are called one, is not the same as that produced by

only one point, but the difference is not great enough to suggest a

different number.

If the difference between one and two were determined by the distance,

then the substitution of lines for knobs of the æsthesiometer ought to

make no difference. And if the sensations produced by two objects fuse

when near together, then the sensations produced by lines ought to

fuse as easily as those produced by knobs.

In regard to the higher numbers difficulties will arise unless we take

the same point of view and say that number is an inference from a

sensation which is in itself a unit. It has been shown that four

points across the ends of the fingers will be called four or less, and

that four points, one on the end of each alternate finger and one at

the base of each of the others, will be called four or more—usually

more. In either case each contact is on a separate finger, and it is

hardly reasonable to suppose there is no diffusion when they are in a

straight row, but that when they are in irregular shape there is

diffusion. It is more probable that the subject regards the sensation

produced by the irregular arrangement as a novelty, and tries to

separate it into parts. He finds both proximal and distal ends of his

fingers concerned. He may discover that the area covered extends from

his index to his little finger. He naturally infers, judging from past

experience, that it would take a good many points to do that, and

hence he overestimates the number. When a novel arrangement was given,

such as moving some of the weights back on the wrist and scattering

others over the fingers, very little idea of number could be gotten,

yet they were certainly far enough apart to be felt one by one if a

person could ever feel them that way, and the number was not so great

as to be entirely unrecognizable.

*

THE SUBJECTIVE HORIZON.

BY ROBERT MACDOUGALL.

I.

The general nature of the factors which enter into the orientation of

the main axes of our bodies, under normal and abnormal conditions, has

been of much interest to the psychologist in connection with the

problem of the development of space and movement perception. The

special