Some concern with self-esteem, social status, and accomplishment is a universal part of human psychology. Moreover, there are few people who are entirely free of egotistical or insecure behavior. Thus we can see Narcissistic Personality Disorder as an extreme point on a range of behavior that includes normal human tendencies. Moreover, there is a fair amount of research that shows that some degree of narcissism can be adaptive. In a 1984 study by Robert Emmons, several narcissistic traits were correlated with measures of adaptive personality traits, such as self-confidence, extraversion, initiative, and ambition. Moreover, in a 2008 study by Eric Russ and colleagues, the authors identified three subtypes of narcissistic personality disorder, which they labeled grandiose/malignant, fragile, and high-functioning/exhibitionistic. The third subtype showed significantly less psychopathology and much higher adaptive functioning than the other two groups. Thus, some degree of narcissism may be adaptive with regard to ambition, initiative, and self-confidence. People with severe narcissistic traits, however, have significant interpersonal, emotional, and even occupational difficulties.