Examining the criterion and incremental validity of the MMPI-3 Self-Importance scale.

The Minnesota Multiphasic Personality Inventory–3 (MMPI-3) is the most recent installment in the MMPI family of instruments. It contains a new scale, Self-Importance (SFI), which was designed to assess grandiosity. Although initial data in the MMPI-3 Technical Manual have been supportive of its construct validity, no published research studies have evaluated this scale to date. The current study examined the internal structure, criterion validity, and incremental validity of the SFI scale in a large sample (n = 645) of university students. The 10 SFI items loaded on one latent factor in a well-fitting model, and item response theory parameters indicated good information coverage across a broad range of the underlying construct. SFI scale scores correlated with several measures of narcissistic personality disorder and grandiose narcissism, but were weakly associated with vulnerable narcissism scales. The SFI scale scores also accounted for incremental variance in a range of criterion measures above and beyond scores of other MMPI-3 Specific Problems scales and the MMPI-3 Personality Psychopathology Five scales. The current finding supported the SFI scale as a distinct and complementary measure of grandiosity for the MMPI-3.