Sixteen Experimental Investigations from the Harvard Psychological Laboratory, Hugo Münsterberg [top fiction books of all time TXT] 📗

it seems not improbable that the light was too

strong an excitement and thus inhibited action. There is also the

probability that the frog was constrained by being placed in a small

box and having the experimenter near.

 

III. SUMMARY.

 

1. The green frog is very timid and does not respond normally to most

stimuli when in the presence of any strange object. Fright tends to

inhibit movement.

 

2. That it is able to profit by experience has been proved by testing

it in simple labyrinths. A few experiences suffice for the formation

of simple associations; but in case of a series of associations from

fifty to a hundred experiences are needed for the formation of a

perfect habit.

 

3. Experiment shows that the frog is able to associate two kinds of

stimuli, e.g., the peculiar tactual stimulus given by a wire and a

painful electric stimulus which in the experiments followed the

tactual. In this case the animal learns to jump away, upon receiving

the tactual stimulus, before the experimenter gives the electric

stimulus.

 

4. Vision, touch and the organic sensations (dependent upon direction

of turning) are the chief sensory factors in the associations. The

animals discriminate colors to some extent.

 

5. Perfectly formed habits are hard to change.

 

6. Fear interferes with the formation of associations.

 

7. Associations persist for at least a month.

 

PART II. REACTION TIME OF THE GREEN FROG TO ELECTRICAL AND TACTUAL

STIMULI.

 

IV. THE PROBLEMS AND POSSIBILITIES OF COMPARATIVE REACTION-TIME

STUDIES.

 

Animal reaction time is at present a new field of research of evident

importance and full of promise. A great deal of time and energy has

been devoted to the investigation of various aspects of the time

relations of human neural processes; a multitude of interesting facts

have been discovered and a few laws established, but the results seem

disproportionate to the amount of patient labor expended.

Physiologists have determined the rate of transmission of the neural

impulse for a few animals, and rough estimates of the time required

for certain changes in the nervous system have been made, but this is

all we have to represent comparative study. Just the path of approach

which would seem most direct, in case of the time of neural changes,

has been avoided. Something is known of the ontogenetic aspect of the

subject, practically nothing of the phylogenetic; yet, in the study of

function the comparative point of view is certainly as important as it

is in the study of structure. In calling attention to the importance

of the study of animal reaction time I would not detract from or

minimize the significance of human investigations. They are all of

value, but they need to be supplemented by comparative studies.

 

It is almost impossible to take up a discussion of the time relations

of neural processes without having to read of physiological and

psychological time. The time of nerve transmission, we are told, is

pure physiological time and has nothing whatever to do with psychic

processes; the time occupied by the changes in brain centers is, on

the contrary, psychological time. At the very beginning of my

discussion of this subject I wish to have it clearly understood that I

make no such distinction. If one phase of the neural process be called

physiological time, with as good reason may all be so named. I prefer,

therefore, to speak of the time relations of the neural process.

 

Of the value of reaction-time studies, one may well believe that it

lies chiefly in the way of approach which they open to the

understanding of the biological significance of the nervous system.

Certainly they are not important as giving us knowledge of the time of

perception, cognition, or association, except in so far as we discover

the relations of these various processes and the conditions under

which they occur most satisfactorily. To determine how this or that

factor in the environment influences the activities of the nervous

system, and in what way system may be adjusted to system or

part-process to whole, is the task of the reaction-time investigator.

 

The problems of reaction time naturally fall within three classes:

Those which deal with (1) nerve transmission rates; (2) the time

relations of the spinal center activities, and (3) brain processes.

Within each of these groups there are innumerable special problems for

the comparative physiologist or psychologist. Under class 1, for

instance, there is the determining of the rates of impulse

transmission in the sensory and the motor nerves, (a) for a variety

of stimuli, (b) for different strengths of each stimulus, (c) for

different conditions of temperature, moisture, nourishment, fatigue,

etc., in case of each stimulus, (d) and all this for hundreds of

representative animals. From this it is clear that lines of work are

not lacking.

 

Closely related to these problems of rate of transmission are certain

fundamental problems concerning the nature of the nerve impulse or

wave. Whether there is a nerve wave, the reaction-time worker has as

favorable an opportunity to determine as anyone, and we have a right

to expect him to do something along this line. The relations of the

form of the nerve impulse to the rhythm of vital action, to fatigue

and to inhibition are awaiting investigation. Some of the most

important unsettled points of psychology depend upon those aspects of

neural activities which we ordinarily refer to as phenomena of

inhibition, and which the psychologist is helpless to explain so long

as the physiological basis and conditions are not known.

 

Then, too, in the study of animals the relation of reaction time to

instincts, habits, and the surroundings of the subject are to be

noted. Variability and adaptability offer chances for extended

biological inquiries; and it is from just such investigations as

these that biology has reason to expect much. The development of

activity, the relation of reflex action to instinctive, of impulsive

to volitional, and the value of all to the organism, should be made

clear by reaction-time study. Such are a few of the broad lines of

inquiry which are before the comparative student of animal reaction

time. It is useless to dwell upon the possibilities and difficulties

of the work, they will be recognized by all who are familiar with the

results of human studies.

 

In the study of the time relations of neural processes Helmholtz was

the pioneer. By him, in 1850, the rate of transmission of the nerve

impulse in the sciatic nerve of the frog was found to be about 27

meters per second[4]. Later Exner[5] studied the time occupied by

various processes in the nervous system of the frog by stimulating the

exposed brain in different regions and noting the time which

intervened before a contraction of the gastrocnemius in each case.

Further investigation of the frog’s reflex reaction time has been made

by Wundt[6], Krawzoff and Langendorff[7], Wilson[8] and others, but in

no case has the method of study been that of the psychologist. Most of

the work has been done by physiologists who relied upon vivisectional

methods. The general physiology of the nervous system of the frog has

been very thoroughly worked up and the papers of Sanders-Ezn[9],

Goltz[10] Steiner[11] Schrader[12] and Merzbacher[13],[14] furnish an

excellent basis for the interpretation of the results of the

reaction-time studies.

 

[4] Helmholtz, H.: ‘Vorläufiger Bericht über die

Portpflanzungsgeschwindigkeit der Nervenreizung.’ _Arch. f.

Anal. u. Physiol._, 1850, S. 71-73.

 

[5] Exner, S.: ‘Experimentelle Untersuchung der einfachsten

psychischen Processe.’ Pflüger’s Arch., Bd. 8. 1874, S.

526-537.

 

[6] Wundt, W.: ‘Untersuchungen zur Mechanik der Nerven und

Nervencentren.’ Stuttgart, 1876.

 

[7] Krawzoff, L., und Langendorff, O.: ‘Zur elektrischen

Reizung des Froschgehirns.’ Arch. f. Anal. u. Physiol.,

Physiol. Abth., 1879, S. 90-94.

 

[8] Wilson, W.H.: ‘Note on the Time Relations of Stimulation of

the Optic Lobes of the Frog.’Jour. of Physiol., Vol. XI.,

1890, pp. 504-508.

 

[9] Sanders-Ezn: ‘Vorarbeit für die Erforschung des

Reflexmechanismus in Lendentmark des Frosches.’ _Berichte über

die Verhandlungen der Kgl. sächs. Gesellsch. d. Wissensch. zu

Leipzig_, 1867, S. 3.

 

[10] Goltz, F.: ‘Beiträge zur Lehre von den Functionen der

Nervencentren des Frosches.’ Berlin, 1869, 130 S.

 

[11] Steiner, J.: ‘Untersuchungen über die Physiologie des

Froschhirns.’ Braunschweig, 1885, 127 S.

 

[12] Schrader, M.G.: ‘Zur Physiologie des Froschgehirns.’

Pflüger’s Arch., Bd. 41, 1887, S. 75-90.

 

[13] Merzbacher, L.: ‘Ueber die Beziebungen der Sinnesorgane zu

den Reflexbewegungen des Frosches.’ Pflüger’s Arch., Bd. 81,

1900, S. 223-262.

 

[14] Merzbacher, L.: ‘Untersuchungen über die Regulation der

Bewegungen der Wirbelthiere. I. Beobachtungen an Fröschen.’

Pflüger’s Arch., Bd. 88, 1901, S. 453-474, 11 Text-figuren.

 

In the present investigation it has been my purpose to study the

reactions of the normal frog by the reaction-time methods of the

psychologist. Hitherto the amount of work done, the extent of

movements or some other change has been taken as a measure of the

influence of a stimulus. My problem is, What are the time relations of

all these reactions? With this problem in mind I enter upon the

following program: (1) Determination of reaction time to electrical

stimuli: (a) qualitative, (b) quantitative, (c) for different

strengths of current; (2) Determination of reaction time to tactual

stimuli (with the same variations); (3) Auditory: (a) qualitative,

(b) quantitative, with studies on the sense of hearing; (4) Visual:

(a) qualitative, (b) quantitative, with observations concerning

the importance of this sense in the life of the frog, and (5)

Olfactory: (a) qualitative, (b) quantitative.

 

The present paper presents in rather bare form the results thus far

obtained on electrical, tactual, and auditory reaction time;

discussion of them will be deferred until a comparison of the results

for the five kinds of stimuli can be given.

 

V. METHOD OF STUDY.

 

The measurements of reaction time herein considered were made with the

Hipp Chronoscope. Cattell’s ‘Falling Screen’ or ‘Gravity Chronoscope’

was used as a control for the Hipp. The Gravity Chronoscope consists

of a heavy metal plate which slides easily between two vertical posts,

with electrical connections so arranged that the plate, when released

from the magnet at the top of the apparatus, in its fall, at a certain

point breaks an electric circuit and at another point further down

makes the same circuit. The rate of fall of the plate is so nearly

constant that this instrument furnishes an accurate standard time with

which Hipp readings may be compared, and in accordance with which the

Hipp may be regulated. For, since the rate of a chronoscope varies

with the strength of the current in use, with the variations in

temperature and with the positions of the springs on the magnetic bar,

it is always necessary to have some standard for corrections. In these

experiments the time of fall of the gravity chronoscope plate, as

determined by the graphic method with a 500 S.V. electric tuning fork,

was 125[sigma] (i.e., thousandths of a second).

 

This period, 125[sigma], was taken as a standard, and each hour,

before the beginning of reaction-time experiments, the time of the

plate’s fall was measured ten times with the Hipp, and for any

variation of the average thus obtained from 125[sigma], the standard,

the necessary corrections were made by changing the position of the

chronoscope springs or the strength of the current.

 

The standard of comparison, 125[sigma], is shorter than most of the

reaction times recorded, but since the time measured was always that

from the breaking to the making of the circuit passing through the

chronoscope it cannot be urged that there were errors resulting from

the difference of magnetization which was caused by variations in the

reaction time. But it is evident that the danger from differences in

magnetization, if such exists, is not avoided in this way; instead,