We all know people who tend to take the bigger half of the cookie. Will they ever become more generous? Well, maybe. Science says they could be stuck with certain (selfish) personality traits for life.
A University of Exeter study published in this month’s Animal Behavior focused on temperaments of mongooses (you know, the bigger cousins of meerkats) and found that selfless or selfish personalities last over the course of their lives.
Researchers measured the time a group of male mongooses spent selfishly guarding their mates versus the time they spent taking care of offspring. (Because mongooses are cooperative breeders — meaning they all pitch in to rear pups regardless of gender or parental status — their caretaking of babies was an example of their selfless, cooperative side.) The results showed that individual male mongooses' guarding vs. caring behaviors remained consistent for the entirety of the study, suggesting each mongoose's unique level of self-interest or selflessness persisted.
While this study only covers furry little mammals, larger mammals (hi, humans) may want to take note: Other research has found that some human traits are decidedly difficult to shake, partly due to heritability. And they get even harder to change after what one study deems a "personality stability plateau" around age 30. In particular, research shows that we can expect our levels of agreeableness and conscientiousness (i.e. our propensities for kindness and selflessness) to rise a bit as we age, but we don't have that much wiggle room to work with.
One event that spurred selfishness in the mongooses was the prospect of finding and keeping a mate, which is notable when compared to the fact that humans are at our lowest level of conscientiousness in our own intro-to-dating period, adolescence. Though the same studies have shown that levels of agreeableness and conscientiousness do have room to grow after those moody teen years, narcissism (a trait that falls under the selfish umbrella) may actually remain constant over a lifetime — especially if we're willful narcissists (those who openly indulge in grandiose shows of ego and manipulation).
If you're trying to break out of that "me, me, me" mentality, just know this: While mongooses (and narcissists) may be unchangeable, most of humans can take advantage of our young adulthood to grow, help others, and become kinder people. So get to it.
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