ABSTRACT
This chapter describes and compares three hypotheses that deal with the disruptive effects of unpredictable and uncontrollable shock on an organism’s behavior. Three hypotheses have been offered: Preparatory response, safety signal, and uncertainty reduction. The uncertainty reduction hypothesis claims that organisms are motivated to reduce uncertainty. This hypothesis makes very similar predictions to the safety signal hypothesis, with two exceptions. The most direct confirmation of the safety signal hypothesis comes from observations of the amount and temporal distribution of fear during predictable and unpredictable shock. Several dependent variables have been used as indices of “fear” in these studies: suppression of bar pressing for food, suppression of licking or “basal emotional level”, and galvanic skin response. All three hypotheses under consideration predict preference for predictable over unpredictable shock. The safety signal hypothesis predicts this because unsignaled shock engenders chronic fear, whereas signaled shock engenders fear only during the signal for shock and no fear in the absence of the signal.
