What life experience is more immersive than marriage, more prolonged than college, more tightly regimented than the average job? Ah yes — military service, which starts with recruiters boldly announcing their intention to make a new man of every trainee. Surely drill sergeants believe they can change personalities.
But psychologists generally believe that our personalities don’t change much over time. Just sticking to the Big Five, we remain mostly agreeable, extroverted, conscientious, neurotic, and open-minded throughout our lives.
“A lot of the discussion in the literature is that personality is so stable, if you go to college, or get married, your personality doesn’t rearrange in this new environment,” said Josh Jackson, an assistant professor of psychology at Washington University in St. Louis. “The question that we attacked was, ‘OK, what’s one of the most extreme experiences you could have?’
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“One of the goals of the military to break down the mentality you had in the outside world, and they’re going to build you up as a soldier,” Jackson said. “If you’re going to find some life experience leading to changes in personality traits, it seems like one of the best environments for that to happen would be the military experience.”
Jackson and several colleagues in Germany tested this hypothesis on a group of 1,300 German men, about 250 of whom went into the military. The researchers followed them over a period of six years, giving them personality self-assessments at four points (you may be familiar with these questionnaires that ask how much you hate going to parties and love following rules, etc.).
In findings published in the journal Psychological Science, the researchers conclude that the military does change a soldier’s personality.
It makes him less agreeable (although it doesn’t noticeably impact other personality dimensions).
This seems logical. Agreeableness is also related to aggression, and in a sense this is one of the instincts the military must instill in people to make them successful soldiers. But what happens to these soldiers after they leave the military?
“That was one of our main questions,” Jackson said. “OK, if the military does change you, once you’re back in the real world, do you kind of snap back to your original personality?”
You do not, according to the researchers’ results. This effect stays with them even some years after they have gone back to school or entered the civilian work force.
The military attracts certain personality types in the first place, including people who tend to be lower in agreeableness, as well as generally less anxious and less open to new experiences (in other words, people who like rules). But in controlling for these self-selection biases, the researchers still found that military service leaves a lasting impression on the personalities of people in a way that few other experiences do.
Jackson can’t say if the same would be true of female soldiers, and the study focused only on Germans. (Keep in mind the Bundeswehr is relatively active in supporting peacekeeping missions around the world, including Afghanistan.) But there is reason to believe the same process would be true of similar military experiences like the American one.
The authors couldn’t pinpoint the precise piece of military life that causes this change. But Jackson suspects it may be the training process itself, and not necessarily the result of specific combat experiences. These subtle personality changes touch on a distinctly different phenomenon than post-traumatic stress disorder, which may leave an injured veteran with what looks a lot like a dramatically different personality.
“This is something that would be a gradual change, that would be pretty much unnoticed,” Jackson said. “These effects aren’t large. It’s not that someone would come out really feeling that their personality has changed so much that they need to go get help.”
But even as these changes are small, the cumulative impacts (and policy implications) could be significant. Agreeableness is associated with several important life outcomes, including the success of interpersonal relationships (and, by extension, the success of marriages).
“It’s a slight change, but you’re taking your personality into every situation that you will go into,” Jackson said. “That’s with you for the rest of your life.”
It’s striking that military service can have this long-lasting effect on people. But, on the other hand, this research also underscores that it’s really difficult to change a person’s personality. If military service is one of the most intensive experiences imaginable, and the best the military can do is a modest change on the one dimension of agreeableness, what does that say about our individual prospects for becoming, say, more outgoing, or to exercise more regularly, or to finally quit smoking?
“It kind of flies in the face,” Jackson said, “of how some people wish that they had more control over changing just who they are.”