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Date of Award


Degree Type

Dissertation (On-Campus Access Only)

Degree Name

Doctor of Psychology (PsyD)


The purpose of this study was to clarify the differences between incestuous biological fathers and incestuous step-fathers. The groups were compared via multiple stepwise discriminant function analyses that utilized demographic information, offense data, and Minnesota Multiphasic Personality Inventory (MMPI) profiles.

Subjects were randomly selected from a pool of incestuous fathers referred for psychological evaluations to a private, Northwest, out-patient psychology office. The sample consisted of 50 biological fathers and 50 stepfathers. All of the fathers admitted to sexually offending against minor aged female children in their families.

Contrary to the hypotheses of this study, the results did not reveal significant differences between groups. The mean and modal MMPI profiles did not reflect psychopathology (T scores > 70). Neither did biological and stepfather incest offenders differ in terms of specific MMPI two-point code types. With the exception of more frequent marriages, stepfather offenders did not appear more impulsive, antisocial, or unstable than their biological counterparts. Even though the hypotheses were not supported, the overall stepwise discriminant analysis was able to differentiate between groups at an accuracy rate of seventy-five percent. The results were discussed in terms of clinical implications and directions for future research.