Openness/intellect: The weirdest trait in the Big Five world?

Openness/intellect often stands apart from the other Big Five/Six personality traits. Here, we interrogate its ‘weirdness.’ First, we discuss openness/intellect’s weird history, highlighting unresolved controversies critical to its interpretation. Second, we identify research questions where openness/intellect is weird among the Big Five: it is the least straightforward predictor of outcomes, often irrelevant to mental health, and the rarest target of volitional change. We distill these findings into three propositions that refine openness/intellect’s role in personality theory. Third, we synthesize etic (imported) and emic (local) evidence implicating openness/intellect as the WEIRDest Big Five trait, the least portable across cultural contexts. We hypothesize how cultural individualism and looseness modify the trait’s relevance and structure. We conclude by arguing for openness/intellect’s weirdness as a feature, not a bug: Some trait components may be universal, and those that aren’t illustrate through contrast how culture shapes personality expression.