1. Personality traits are real. They are not just theoretical constructs or labels conjured up to account for or explain certain behaviors. They exist inside each person.
2. Traits determine or cause behavior, guiding its course. Traits do not come into existence only in response to appropriate stimuli. They direct us to seek out certain stimuli, and they interact with the environment to produce behavior.
3. Traits can be demonstrated empirically. Because traits are real, it should be possible to verify their existence and nature, even though the traits themselves cannot be seen. By observing a person's behavior over time we can infer evidence of traits in the coherence and consistency of that person's responses to the same similar stimuli. or
4. Traits are not rigidly separated from one another-only relatively so. Traits may overlap; although they represent different characteristics, they often correlate highly with one another. For example, aggressiveness and hostility are separate traits, but they are also closely related. They are frequently observed to occur together in a person's behavior.
5. Traits vary with the situation. They "are often aroused in one type of situation and not in another, not all stimuli are equivalent in effectiveness" (Allport, 1937, pp. 331-332). For example, a person may display the trait of meticulousness in one kind of situation and the trait of disorderliness in another kind of situation.