Psychosomatic Medicine 1:293-308 (1939)
© 1939 American Psychosomatic Society

The Production of "Experimental Neurosis" in the White Rat

¹ Psychiatric Clinic for Children, University of Minnesota Hospitals and Department of Psychology, University of Minnesota

As a consequence of continued contact with a stressful situation, three of a group of six white rats developed, disorders of behavior. Although these disorders formed a different pattern in each animal, all have been considered manifestations of an "experimental neurosis", this expression having been defined to mean "any chronic, abnormal behavior, experimentally produced".

The experimental situation and its stressful elements were as follows: The rats were strapped to a stand so that the only sizeable limb movement possible was a flexion of the right foreleg. Under certain conditions such a flexion was rewarded with a food pellet; under other conditions it was punished with an electric shock.

Observation indicated that the animals experienced two principal stresses: the first, when they were required to delay the food-bringing flexion until they received a bright-light stimulus; the second, when they were required to make a very difficult discrimination between a bright-light stimulus which permitted a food-bringing flexion and a dim-light stimulus which prohibited such a flexion on pain of shock. Because, under such conditions, the organism was receiving simultaneously stimuli to the excitation and inhibition of the same response, the stresses experienced have been characterized as comprising a "clash" between the neural activity of initiating a response and the neural activity of inhibiting the same response.

A comparison of this successful experiment with three previous experiments led to the belief that to produce enduring disturbances it is necessary to limit activity as much as possible to the critical response. This carries the implication that extraneous activity in some way negates the neural effects produced in the stressful situation.

Rat No. I developed the following behavior disturbances: 1) An increasing tendency to react to the problem by a regular but temporary loss of the capacity to inhibit flexions of the foreleg. 2) Spontaneous, loud squealing accompanied by general body and tail stiffening. 3) An exaggerated jumpiness and tendency to stiffen when touched. 4) A practice of inhibiting postural reflexes (holding poses) for long periods when in contact with the experimenter's hand. 5) A tendency to squeal when touched or lifted. 6) An active avoidance of the experimenter's hand in the living cage.

Rat No. 2. showed the following changes in behavior: 1) An increasing tendency to react to the problem by a regular, but temporary, loss of the capacity to flex the foreleg. 2) Greatly decreased activity in the cage, including sleepiness and an indifference to certain stimuli normally adequate to excite exploratory behavior.

Disorders of behavior observed in Rat No. 3 are: 1) The loss of a previous habit of eating while strapped in the apparatus. 2) Struggling in the apparatus so continuously and so violently that further experimentation was useless. 3) Greatly decreased activity in the cage, including sleepiness and indifference to certain stimuli normally adequate to excite exploratory behavior.

Although the data are as yet very limited, it seems possible to offer the following tentative conclusions:

When presented over a period of time with a single stimulus or simultaneous stimuli to mutually antagonistic responses, a certain proportion of white rats will develop an "experimental neurosis".

It is necessary to the development of an "experimental neurosis" that activity other than that of the responses utilized in the stressful situation be very limited.

In the white rat the symptoms of "experimental neurosis" may assume a different form from one animal to the next.

Adult white rats possess in varying degree a constitutional predisposition to the development of an "experimental neurosis". This predisposition will, in part, determine the degree of stress necessary to produce the behavior disturbance as well as the pattern of the behavior produced.

In order to avoid any possible misinterpretation by the reader, it seems wise to restate the author's position on the comparative value of these experiments for human psychiatry. It is his conviction that the contributions to be made to psychiatry by the study of this problem will be realized only after the total picture of the appearance and disappearance of experimentally-produced behavior disturbances has been described and understood. From this comprehension of the total process and not from comparisons based on specific details, should come valuable suggestions for explanatory concepts and therapeutic devices.

Note:

This paper was read in abbreviated form before the American Psychological Association meeting in Columbus, Ohio, on September 7-10, 1938. Previously its results had been submitted to the Department of Psychology at the University of Minnesota as a Ph.D. thesis. The writer is indebted to his adviser, Professor W. T. Heron, for much advice and technical assistance.

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