The applicability of inescapable shock as a source of animal depression

Male rats (N = 27) were given initial experience with escapable shock, equivalent amounts of inescapable shock, or no shock. Measures were then obtained in the ensuing 15 hours on food intake, water intake, number of cage crossings, and weight change for all groups. Following this, animals were tested on an escape task. Inescapably shocked animals showed significant decreases in food and water consumption in comparison to both nonshocked and escapably shocked control rats. Weight gains were significantly decreased by exposure to shock irrespective of the availability of a coping response. Consistency of these findings with proposals suggesting that exposure to inescapable shock leads to a state of animal depression (learned helplessness) is discussed and compared to alternative stress explanations.