Adaptive significance of low levels of self-deception and cooperation in depression

Consciousness and self-awareness, juxtaposed by the ability to self-deceive, are legacies of our evolutionary heritage. As a purposive outgrowth of modularity, self-deception may serve to isolate threatening thoughts from consciousness and facilitate cooperation. The primary goal of the present investigation was to determine if individuals with depression exhibit both low levels of self-deception and cooperation. Relationships between the tendency to self-deceive and the conscious attributions typical of depression or promoting cooperation were also examined. Eighty undergraduate participants completed measures of self-deception, impression management, depression, and attributional styles. Cooperation was assessed by responses to social dilemmas based on the prisoner's dilemma game. Results indicated that, as expected, high self-deceivers cooperated more and exhibited lower levels of depression than low self-deceivers. Self-deception scores were significantly associated with several attributional styles but independently predicted depressive symptomology. That individuals with depression displayed both reduced levels of self-deception and cooperation is discussed in light of several models of the evolutionary significance of depression, especially E. H. Hagen's bargaining model of depression [The functions of postpartum depression. Evolution and Human Behavior, 20, 325–359, 1999; Depression as bargaining: The case postpartum. Evolution and Human Behavior, 23, 323–336, 2002; The bargaining model of depression. In P. Hammerstein (Ed.), Genetic and cultural evolution of cooperation (pp. 95–123). Cambridge, MA: MIT Press, 2003].