Ulcers in Executive Monkeys was a study into the effects of
stress, published in 1958 in ''
Scientific American'' by
Joseph V. Brady Joseph Vincent Brady (March 28, 1922 – July 29, 2011) was an American psychologist, neuroscientist, and pioneer of behavioral pharmacology. In addition to his status as a founder of behavioral pharmacology, he made significant contributions in th ...
.
Method of the experiment
In an early version of the study, Brady placed monkeys in 'restraining chairs' and conditioned them to press a lever.
[Brady, J. V., Porter, R. W., Conrad, D. G., & Mason, J. W. (1958). Avoidance behavior and the development of duodenal ulcers. ''Journal of the Experimental Analysis of Behavior, 1''(1), 69–72. ] They were given
electric shock
Electrical injury is a physiological reaction caused by electric current passing through the body. The injury depends on the density of the current, tissue resistance and duration of contact. Very small currents may be imperceptible or produce ...
s every 20 seconds unless they pressed the lever during the same time period. This study came to an abrupt halt when many of the monkeys died from
perforated ulcers.
To test this Brady used a yoked
control monkey. He placed an 'Executive Monkey' in the restraining chair, which could press the lever to prevent the electric shock. The yoked monkey had no control over the lever, leaving only the 'Executive' with the psychological stress of pushing the lever.
Results
After 23 days of a continuous 6 hours on, 6 hours off schedule of electric shocks, the executive monkey died. Brady then tried various schedules, but no monkeys died from this. He then returned to the original 6 on, 6 off, and tested the stomachs of the Executives and found that their stomach acidity was greatest during the rest period.
The greatest danger occurred when the
sympathetic arousal
The sympathetic nervous system (SNS) is one of the three divisions of the autonomic nervous system, the others being the parasympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of t ...
stopped and the stomach was flooded with
digestive hormones. This was a
parasympathetic
The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of t ...
rebound associated with the
Hypothalamic-pituitary-adrenal axis, which led to the development of ulcers in the Executive monkeys.
In all the variations of the experiment, no yoked control monkey ever developed an ulcer. This suggests that the ulcers were a symptom of the excessive stress induced by having control.
Hans Selye's
General Adaptation Syndrome proposes a similar effect in the Exhaustion phase.
See also
*
Animal testing on non-human primates
Experiments involving non-human primates (NHPs) include toxicity testing for medical and non-medical substances; studies of infectious disease, such as HIV and hepatitis; neurological studies; behavior and cognition; reproduction; genetics; and ...
Notes
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Psychology experiments
Scientific American articles