Concludes that depression consists of low reward motivation and high punisher motivation. The argument is as follows: Clinical observation and research agree that depression is primarily a motivational deficit. Learning theories agree that motivation consists of both the organism's expectations and the outcome's impact (value or aversiveness), i.e., motivation = expectation X impact. Popular theories and research agree that depressed people's expectations and their impacts differ from those of nondepressed people. Depressed people often expect few rewards and many punishers, and the impact of rewards is low while that of punishers is high. By substituting known expectancies and impacts into the motivation equation, it becomes clear that depressed people suffer a motivational deficit. A specific deduction is that depressed people exhibit their most severe motivational deficits in ambiguous social situations. This deduction generates the hypothesis that in ambiguous social situations, depressed people should engage in few instrumental, operant behaviors, but many escape and avoidance behaviors.