Genetic correlates and sex differences in Holtzman Inkblot Technique responses of twins.

Holtzman Inkblot Technique (HIT) responses of 36 monozygotic (MZ), 18 dizygotic same-sex (DZ-S) and 29 dizygotic opposite-sex (DZ-O) college student twin pairs were analyzed. MZ group twins were significantly more alike across a variety of HIT response dimensions than DZ-S or DZ-O group twins. The following variables indicated a possible significant genetic contribution to response determination: Movement, Abstract Content, Hostility, Pathognomic Verbalization and Popular Responses. DZ-O groups data (representing a high degree of control for environmental influences) indicated significant sex differences on the following variables: M less than F -- Rejection, Form Appropriateness, Anatomical Content, and Balance; F less than M -- Human Content and Popular. The results are discussed in terms of (a) comparable genetic determination studies with Rorschach responses and (b) the necessity for separate male and female norms on several HIT scored response scales.