Effects of coping behavior in different warning signal conditions on stress pathology in rats.

Abstract

Rats received electric shock that was preceded by either a warning signal, a series of signals forming an external clock, or no signal at all. In all conditions, subjects which could avoid and/or escape shock developed less ulceration than, did yoked animals which received exactly the same shock (through fixed electrodes wired in series) but had no control over shock. Presence or absence of a warning signal did, however, have an effect: A discrete warning signal reduced the ulceration both of subjects having control over shock and of yoked helpless subjects. A theory is proposed to explain how psychological factors determine the development of gastric ulceration in stress situations, and the present results are examined in relation to it. In 1968 I reported that rats which could avoid or escape electric shocks lost less body weight, developed fewer stomach ulcers, and showed less fear in a stressful situation (as measured by a CER test) than did rats which received exactly the same electric shocks but could not avoid or escape them (Weiss, 1968a). A previous study which had also examined the effects of coping behavior on the development of psychosomatic pathology obtained results opposite to these. Brady, Porter, Conrad, and Mason (1958), in a study which became known as the monkey experiment (Brady, 1958), found that in four pairs of monkeys, animals which could avoid electric shocks eventually developed severe gastrointestinal pathology and died, while animals which received the same electric shocks but could not perform the avoidance response developed no discernible disorders. In the 1968a paper, I discussed the possible reasons why my results were opposite to those of Brady et al. Although the studies in question were carried out on different species, and there was an unfortunate selection factor in the executive monkey experiment (i.e., the avoidance and yoked subjects were not chosen at random but, rather, a 2-4 hr. avoidance pretest was