Sixteen Experimental Investigations from the Harvard Psychological Laboratory - Hugo Münsterberg (best life changing books txt) 📗

class="calibre1">But attention to a dermal stimulation is precisely the condition which

would tend to some extent to prevent this inhibition. For this reason

we might well expect to find the error in estimation more variable,

the ‘constant error’ in general greater, and the specific effects of

variations which would affect the peripheral muscles, more marked in

‘tactual’ time than in either ‘auditory’ or ‘optical’ time. Certainly

all these factors appear surprisingly large in these experiments.

 

It is not possible to ascertain to how great an extent subject Sh

inhibited the more external sensations, but certainly if he succeeded

to an unusual degree in so doing, that fact would explain the absence

of effect of stimulation difference in his case.

 

Explanation has still to be offered for the variable effect of

intensity difference upon the second interval. According to all

subjects except Sn, there is a radical difference in attitude in the

two intervals. In the first interval the subject is merely observant,

but in the second he is more or less reproductive. That is, he

measures off a length which seems equal to the standard, and if the

stimulation does not come at that point he is prepared to judge the

interval as ‘longer,’ even before the third stimulation is given. In

cases, then, where the judgment with equal intensities would be

‘longer,’ we might expect that the actual strengthening or weakening

of the final tap would make no difference, and that it would make very

little difference in other cases. But even here the expectation of the

intensity is an important factor in determining tension changes,

although naturally much less so than in the first interval. So we

should still expect the lengthening of the second interval.

 

We must remember, however, that, as we noticed in discussing the

experiments of Group 2, there is complicated with the lengthening

effect of a change the bare constant error, which appears even when

the three stimulations are similar in all respects except temporal

location. Compare WWW with SSS, and we find that with all five

subjects the constant error is decidedly changed, being even reversed

in direction with three of the subjects.

 

Now, what determines the direction of the constant error, where there

is no pause between the intervals? Three subjects reported that at

times there seemed to be a slight loss of time after the second

stimulation, owing to the readjustment called for by the change of

attitude referred to above, so that the second interval was begun, not

really at the second stimulation, but a certain period after it. This

fact, if we assume it to be such, and also assume that it is present

to a certain degree in all observations of this kind, explains the

apparent overestimation of the first interval. Opposed to the factor

of loss of time there is the factor of perspective, by which an

interval, or part of an interval, seems less in quantity as it recedes

into the past. The joint effect of these two factors determines the

constant error in any case where no pause is introduced between ST

and CT. It is then perfectly obvious that, as the perspective factor

is decreased by diminishing the intervals compared, the constant error

must receive positive increments, i.e., become algebraically

greater; which corresponds exactly with the results obtained by

Vierordt, Kollert, Estel, and Glass, that under ordinary conditions

long standard intervals are comparatively underestimated, and short

ones overestimated.

 

On the other hand, if with a given interval we vary the loss of time,

we also vary the constant error. We have seen that a change in the

intensity of the stimulations, although the relative intensity of the

three remains constant, produces this variation of the constant error;

and the individual differences of subjects with regard to sensibility,

power of attention and inhibition, and preferences for certain

intensities, lead us to the conclusion that for certain subjects

certain intensities of stimulation make the transition from the

receptive attitude to the reproductive easiest, and, therefore, most

rapid.

 

Now finally, as regards the apparent failure of the change in SSW to

lengthen the second interval, for which we are seeking to account; the

comparatively great loss of time occurring where the change of

attitude would naturally be most difficult (that is, where it is

complicated with a change of attention from a strong stimulation to

the higher key of a weak stimulation) is sufficient to explain why

with most subjects the lengthening effect upon the second interval is

more than neutralized. The individual differences mentioned in the

preceding paragraph as affecting the relation of the two factors

determining the constant error, enter here of course to modify the

judgments and cause disagreement among the results for different

subjects.

 

Briefly stated, the most important points upon which this discussion

hinges are thus the following: We have shown—

 

1. That the introduction of either a local difference or a

difference of intensity in the tactual stimulations limiting

an interval has, in general, the effect of causing the

interval to appear longer than it otherwise would appear.

 

2. That the apparent exceptions to the above rule are, (a)

that the increase of the local difference in the first

interval, the stimulated areas remaining unchanged, produces a

slight decrease in the subjective lengthening of the

interval, and (b) that in certain cases a difference in

intensity of the stimulations limiting the second interval

apparently causes the interval to seem shorter than it

otherwise would.

 

3. That the ‘constant error’ of time judgment is dependent

upon the intensity of the stimulations employed, although the

three stimulations limiting the two intervals remain of equal

intensity.

 

To harmonize these results we have found it necessary to assume:

 

1. That the length of a time interval is perceived as the

amount of change in the sensation-complex corresponding to

that interval.

 

2. That the so-called ‘constant error’ of time estimation is

determined by two mutually opposing factors, of which the

first is the loss of time occasioned by the change of

attitude at the division between the two intervals, and the

second is the diminishing effect of perspective.

 

It is evident, however, that this last assumption applies only

to the conditions under which the results were obtained,

namely, the comparison of two intervals marked off by three

brief stimulations.

 

*

 

PERCEPTION OF NUMBER THROUGH TOUCH.

 

BY J. FRANKLIN MESSENGER.

 

The investigation which I am now reporting began as a study of the

fusion of touch sensations when more than two contacts were possible.

As the work proceeded new questions came up and the inquiry broadened

so much that it seemed more appropriate to call it a study in the

perception of number.

 

The experiments are intended to have reference chiefly to three

questions: the space-threshold, fusion of touch sensations, and the

perception of number. I shall deny the validity of a threshold, and

deny that there is fusion, and then offer a theory which attempts to

explain the phenomena connected with the determination of a threshold

and the problem of fusion and diffusion of touch sensations.

 

The first apparatus used for the research was made as follows: Two

uprights were fastened to a table. These supported a cross-bar about

ten inches from the table. To this bar was fastened a row of steel

springs which could be pressed down in the manner of piano keys. To

each of these springs was fastened a thread which held a bullet. The

bullets, which were wrapped in silk to obviate temperature sensations,

were thus suspended just above the fingers, two over each finger. Each

thread passed through a small ring which was held just a little above

the fingers. These rings could be moved in any direction to

accommodate the bullet to the position of the finger. Any number of

the bullets could be let down at once. The main object at first was to

learn something about the fusion of sensations when more than two

contacts were given.

 

Special attention was given to the relation of the errors made when

the fingers were near together to those made when the fingers were

spread. For this purpose a series of experiments was made with the

fingers close together, and then the series was repeated with the

fingers spread as far as possible without the subject’s feeling any

strain. Each subject was experimented on one hour a week for about

three months. The same kind of stimulation was given when the fingers

were near together as was given when they were spread. The figures

given below represent the average percentage of errors for four

subjects.

 

Of the total number of answers given by all subjects when the fingers

were close together, 70 per cent. were wrong. An answer was called

wrong whenever the subject failed to judge the number correctly. In

making out the figures I did not take into account the nature of the

errors. Whether involving too many or too few the answer was called

wrong. Counting up the number of wrong answers when the fingers were

spread, I found that 28 per cent. of the total number of answers were

wrong. This means simply that when the fingers were near together

there were more than twice as many errors as there were when they were

spread, in spite of the fact that each finger was stimulated in the

same way in each case.

 

A similar experiment was tried using the two middle fingers only. In

this case not more than four contacts could be made at once, and hence

we should expect a smaller number of errors, but we should expect

still to find more of them when the fingers are near together than

when they are spread. I found that 49 per cent. of the answers were

wrong when the fingers were near together and 20 per cent. were wrong

when they were spread. It happens that this ratio is approximately the

same as the former one, but I do not regard this fact as very

significant. I state only that it is easier to judge in one case than

in the other; how much easier may depend on various factors.

 

To carry the point still further I took only two bullets, one over the

second phalanx of each middle finger. When the fingers were spread the

two were never felt as one. When the fingers were together they were

often felt as one.

 

The next step was to investigate the effect of bringing together the

fingers of opposite hands. I asked the subject to clasp his hands in

such a way that the second phalanges would be about even. I could not

use the same apparatus conveniently with the hands in this position,

but in order to have the contacts as similar as possible to those I

had been using, I took four of the same kind of bullets and fastened

them to the ends of two æsthesiometers. This enabled me to give four

contacts at once. However, only two were necessary to show that

contacts on fingers of opposite hands could be made to ‘fuse’ by

putting the fingers together. If two contacts are given on contiguous

fingers, they are quite as likely to be perceived as one when the

fingers are fingers of opposite hands, as when they are contiguous

fingers of the same hand.

 

These results seem to show that one of the important elements of

fusion is the actual space relations of the points stimulated. The

reports of the subjects also showed that generally and perhaps always

they located the points in space and then remembered what finger

occupied that place. It was not uncommon for a subject to report a