• life events/stress;
  • behavioral activation;
  • learned helplessness;
  • positive reinforcement;
  • adjunctive behavior;
  • schedule-induced behavior

This paper reviews two learning theory-based models of experiential contributions to depression: response contingent positive reinforcement and learned helplessness. The authors argue that these models connect to a phenomenon that may explain why symptoms of behavioral excess (e.g. rumination) often occur in depression that is otherwise marked by symptoms of behavioral deficit (e.g. anhedonia). Specifically, the authors illustrate that that concept of schedule strain (or low rates of response contingent reinforcement giving rise to low frequencies of behavior) unites these models. Depression is more likely, or more severe, when schedule strain conditions occur in situations containing reinforcers important to the individual and/or when they simultaneously occur in a number of situations. Conditions of schedule strain are known to give rise to adjunctive behaviors: apparently irrelevant, easy behaviors that deliver immediate reinforcement. This paper suggests that, for some depressed individuals, behavioral excess symptoms like rumination and overeating might serve adjunctive functions. Implications of this hypothesis are discussed.