The Optimal Margin of Illusion Hypothesis: Evidence from the Self-serving Bias and Personality Disorders

It was predicted that the Self-Serving Bias (SSB) would be exaggerated by those with certain personality disorders such as narcissism and reduced by those with other personality disorders such as dependency. Participants were volunteer, undergraduate students. After completing the Millon Clinical Multiaxial Inventory (MCMI-III), participants were given a selection from a textbook to learn. Subsequently they were tested on the textbook material and then given false feedback (either an A or an F) about their performance. After seeing their score, participants’ attributions about the cause for the score were measured. The data were analyzed using a series of multiple regressions with the internal-external locus of causality as the criterion variable. Each scale in the MCMI-III was used as a predictor in a separate regression equation along with the success-failure factor, and the interaction of personality scale and the success-failure. Evidence of an unusual self-serving bias would be shown by a significant interaction. Significant interactions of personality disorder and success-failure were found for the narcissistic, histrionic, dependent, and avoidant scales. The analysis of the regression lines for the narcissistic and histrionic scales revealed an increased self-serving for these disorders. dependents and avoidants showed a reduced self-serving bias. The results are discussed in the context of Baumeister’s (1989) optimal margin of illusion.