The initial validation of an internalization and externalization inventory

Internalizing and externalizing in adults are typically assessed via psychopathological symptoms, despite being temperament indicators. This study developed the Internalization and Externalization Inventory (IEI), which measures internalization and externalization as temperamental tendencies to deal with stressors. The IEI was distributed online to 236 adults. Confirmatory Factor Analysis was used to investigate its hypothesized two-factors structure. First, the unidimensionality of the internalization and externalization factors was assessed; items with loadings <0.4 were excluded. For highly correlated or similarly worded items, the one with the lower loading was removed. Subsequent investigation of the multidimensional structure yielded too few items for Externalization. An Exploratory Factor Analysis yielded three Externalization subfactors: External Attribution, Hostile Reactivity and Reward-Seeking Coping. The final IEI, with 8 items for Internalization and 16 for Externalization, showed good internal consistency. Furthermore, convergent and discriminant validity were tested with correlational analyses, using indices of internalizing and externalizing psychopathology, neuroticism, effortful control (EC), and behavioral activation/inhibition. All correlations were in the expected direction and magnitude, except for the associations between Externalization and EC, General Psychological Distress, Neuroticism, Internalizing Psychopathology, as well as between Internalization and Externalizing Psychopathology. However, the Hostile Reactivity subscale, rather than the composite Externalization scale, showed the expected associations. The results indicate the IEI might be a promising instrument to assess internalization and externalization as temperamental constructs, independent from psychopathology.