Who is NOT associated with the trait approach of personality?

The correct option is Sheldon.

To understand why Sheldon is the correct answer, we can look at the psychological theories of personality developed by each of the listed individuals:
1. Costa and McCrae: They are famous for developing the Five-Factor Model (often called the "Big Five" personality traits: Openness, Conscientiousness, Extraversion, Agreeableness, and Neuroticism), which is a cornerstone of the modern trait approach.
2. Allport: Gordon Allport is widely considered the pioneer of the trait approach, categorizing traits into cardinal, central, and secondary traits.
3. Cattell: Raymond Cattell used factor analysis to identify 16 source traits, creating the 16PF (Personality Factors) questionnaire, which is also a trait theory.
4. Sheldon: William Sheldon, on the other hand, is associated with the type approach (specifically, somatotype theory), which links body types (endomorph, mesomorph, and ectomorph) to temperament. Therefore, he is not associated with the trait approach.