Amid all the bad news about replication in psychology, it’s easy to think that all psychological findings are questionable. That’s not true. In 2019, psychologist Chris Soto made a list of associations between personality traits and what have been called 「consequential life outcomes」 in the literature. These include things ranging from depression to heart disease to healthy attachment with a romantic partner. Of the 78 associations previously published, 87 percent replicated. That gives good reason to be confident in the literature on personality psychology.
The most famous replication project in psychology, the 2015 Open Science Collaboration project that examined 97 effects primarily in social and cognitive psychology, found a replication rate of only 37 percent. There have been some successful replications of important research, several studies by Nobel Prize winner Daniel Kahneman replicated well, but there have been many other instances of prominent studies failing to replicate. Personality stands out, then, as a more reliable area of psychology.
It’s also important to note that, even when psychology studies do replicate, the replication often finds a smaller effect size. This suggests that the effects reported in original studies are often overstatements of the true effect. For example, the 2015 replication project found that replication effects were only about 40 percent as big as the originally reported one. In this personality replication, however, the effects were about 80 percent as big as the originally reported one. Personality psychology seems to be getting much closer to the true effect in their studies.
What are these personality effects? You can read the full list of 78 effects in the manuscript, but I』ll list out several of the effects that are largest (and most interesting to me), organized by trait.
Extraversion:
People who were more extraverted reported being:
More satisfied with their lives
More accepted by peers
Having higher social status
More committed to their jobs
Having stronger leadership skills
More frequent volunteers
It’s no surprise that being outgoing is related to good social outcomes, like popularity and acceptance, but it’s also important to note that extraversion is related to feeling happier and more content with a job.
Agreeableness:
People who were more agreeable reported:
Feeling more gratitude
Forgiving others more often
Having fewer personality disorders
Having stronger leadership skills
Having stronger religious beliefs
As you might expect, being more agreeable was related to getting along better with others. Perhaps more surprising was its replicated relationship with religious beliefs.
Conscientiousness:
People who were more conscientious reported:
Caring more about internal feelings of success
Engaging in less antisocial and criminal behavior
Being slightly more politically conservative
Being slightly happier in their relationships
Conscientiousness is related to being more responsible and persevering more, which can lead to feeling more successful in work and in romantic relationships, and make you less likely to make poor or risky choices. It’s also known to be related to political leanings.
Neuroticism:
People who were more neurotic reported:
Being less satisfied with their lives
Being more anxious
Being more depressed
Caring less about internal feelings of success
Having less financial security
Being less committed to their jobs
Neuroticism indicates emotional instability and a tendency to experience more negative emotions overall, which is related to problems with mental health, satisfaction with work and life success, and even being financially secure.
Openness to Experiences:
People who were more open reported:
Having more interest in artistic jobs
Having less authoritarian political views
Being slightly more liberal
Feeling like they have stronger 「identity consolidation」 (healthy development of their identity)
Openness is related to intellectual curiosity, which can influence what people prefer to do for work, their political views, and their sense of who they are.
Why was personality psychology more reliable than social psychology? Factors related to the way that personality psychologists are trained and promoted are likely relevant. First, personality psychologists generally agree on what they mean by personality and how to measure it. Personality is almost always conceptualized in terms of the Big Five traits, and these are almost always measured using one of only a few validated personality tests.
This regularity might seem stifling to a social psychologist, who is used to elaborate staged situations being used to measure their variables, and to running tests using many different versions of these situations. (For example, you might measure 「helpfulness」 by dropping a bunch of pens and counting how many a study participant picked up, or you might measure it by seeing if a participant is willing to stay after the end of the study, or even seeing if they’re willing to donate money.) For creating reliable scientific knowledge, however, regularity is key. It means that we can typically rule out that the relationship between personality and an outcome is due to something weird about how it was measured (what Meehl called 「auxiliary assumptions」). We know personality measures are pretty good, so the effect is more likely to be due to real psychological factors.
The other key factor is the geekiness of personality psychologists. Constructing personality tests, unlike creating complex situations, tends to be a stats-heavy endeavour. Just to understand where the Big Five come from, you have to learn foreboding concepts like Principal Components Analysis, and that typically leads you to other complex statistical techniques. All this attention to technical detail means that personality researchers invest their energy in getting the measurement properties of their studies right, while focusing less on creating dramatic situations that capture the imagination. It’s more boring, but it also leads to a more careful, cumulative science.