A content validity study of the defense mechanism inventory

The content validity of the Defense Mechanism Inventory was tested by 20 raters who evaluated each item in terms of which 15 defenses and three ego threats it represented. Items purportedly measuring the global defense categories of principalization, turning against self, and reversal, achieved relatively high rater agreement (over 70%) while projection and turning against Object fared poorly (29% and 39% respectively). Differential content validity was found in the levels and areas of the Inventory, indicating that the context in which items appear affect their representativeness of defensive behaviors. The individual defense mechanisms were disproportionately represented by the Inventory. Ratings suggested that aggressiveness was the major ego threat being measured by the items. Most of the problems appear correctable through rewriting many of the items.