Stress of predictable and unpredictable shock.

Abstract

This article examines the claim that unpredictable shock is more stressful than predictable shock in short-term studies (Abbott, Schoen, & Badia, 1984). These authors' classification of studies as short or long term, their conceptualization of them as predictability studies, and their failure to note contrary evidence are discussed. The conclusion is that predictable shock (the presence of a warning signal before shock) makes the situation more stressful both in short-and long-term studies. Conflicting results are most likely due to the presence of additional and confounding variables in contrary studies.Stress has been one of the most prolific areas of research for many different sciences; Selye (1976) had counted over 110,000 studies on stress by 1976. One of the continuing questions in stress research in psychology is the effect of the presence of a warning signal (WS). Do organisms suffer more stress when inescapable unpleasant events are preceded by a WS, or do they suffer more stress when there is no WS? In short, is it better to know or not to know that something unavoidable is about to happen? This is an important question for psychology in general, and not just for animal research. The issue of whether the presence of a WS is more aversive and more stressful than its absence has been reviewed several times with reference to behavioral measures of aversiveness and stress (Averill, 1973;

Stress, Predictability, and Oral Fentanyl Self-Administration in Female and Male Rats

“…Using an operant paradigm, female and male rats were tested for drug SA with and without predictable or unpredictable acute and repeated stress. Consistent with earlier behavioral, immunological, and physiological reports (Abbott et al , 1984;Arthur, 1986;Glass & Singer, 1972;McKinnon et aI., 1989), predictability had a different effect on drug SA depending on whether the stressor was acute or chronic. Specifically, predictability of the stressor increased fentanyl SA with repeated exposure to the stressor, especially for female subjects.…”

“…For example, Glass and Singer (1972) reported a series of human laboratory studies which found that predictability of a noise stressor attenuated the performance decrements that occurred after cessation of an acute unpredictable nois8 stressor . In contrast, under conditions of chronic stressor exposure, predictability potentiated behavioral , physiological, biochemical, and immunological stress responses (Abbott, Schoen, & Badia, 1984;Arthur, 1986;McKinnon, Weisse, Reynolds, Bowles, & Baum, 1989). This increase with repeated exposure to a stressor might reflect: (1) sensitization to the stressor; or (2) classical conditioning between the stimuli that predict the stressor and the stressor itself ( Pavlov, 1906;Rescorla, 1966;Rescorla, 1967).…”

“…Rationale: It has been reported that, under conditions of repeated stressor exposure or chronic stress, predictability of a stressor may enhance stress responses (Abbott, Schoen, & Badia, 1984;Arthur, 1986;McKinnon, Weisse, Reynolds, Bowles, & Baum, 1989). Therefore, animals in the predictable stress conditions should SA more fentanyl in response to the experience of higher stress.…”

“…Rationale: Under chronic conditions of stressor exposure, predictability has been reported to potentiate responses to stress (Abbott, Schoen, & Badia, 1984;Arthur, 1986). Body weight and water consumption were measured daily throughout the experiment.…”

Effects of predictability on the welfare of captive animals

“…Third, studies have used preference testsgiving the animals choice between, for example, predictable and unpredictable electric shock. These tests provide a clear indication of the animals' preference, but they are not without their critics (Arthur, 1986, and see Fraser and Matthews, 1997 for a review).…”