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