It’s amazing that so many things we share in common can be made into memes we can laugh about. Naturally, while some are way funnier to certain people, others might fall completely flat. That’s okay though, we all have different personalities. But where do they come from exactly, and what dictates which personality we’ll get?
The answer is a mix of nature and nurture, though figuring out how much of each has been tricky for scientists. For decades, researchers studied twins to crack this code. The basic idea is simple: identical twins share 100% of their genes, while fraternal twins share about 50%. If identical twins are more similar than fraternal twins, genes must matter.
The famous Minnesota Twin Study ran from 1979 to 1999, looking at twins separated at birth and raised by different families. The study examined various traits like height, weight, IQ, and rate of speech, finding for example that about 70 percent of IQ differences were due to genetics.
When it comes to the Big Five personality traits specifically (openness, conscientiousness, extraversion, agreeableness, and neuroticism), twin studies have found that about 40 to 60 percent of the differences between people come from genetic factors.
Berit Brogaard, D.M.Sci., Ph.D., a professor and the director of the Brogaard Lab for Multisensory Research at the University of Miami, suggests this happens because twin studies can overestimate heritability when changes in society or technology connect a learned behavior to an inherited trait.
If that sounds confusing, think about basketball. Being tall is genetic, and tall people join basketball teams more often. If you studied twins, you might think joining basketball teams is genetic too, but that’s ridiculous because basketball was invented fairly recently, in the grand scheme of things.
Maybe the same thing happens with personality, where certain inherited physical traits only matter because of how society works today.
However much genetics influence personality, the rest comes down to what happens around you. And there’s real-life evidence for that. A study from the University of Edinburgh followed over 2,200 British twins from birth to age 18 and found that kids who grew up with more maternal warmth tended to become more open-minded and agreeable later on.
So even when two people share the same DNA, differences in how they’re treated while growing up can still shape who they become.
What about humor though? Is being funny something you’re born with? A 2025 twin study led by Gil Greengross tried to tackle this question.
The researchers had hundreds of twin pairs rate their own humor abilities and write funny captions for blank cartoons. When it came to people thinking they were funny, genes did play some role.
But when judges actually scored how funny the captions were, the results were surprising. Being genuinely funny seems to be something you learn through practice and exposure rather than inherit.
At the same time, scientists have also found small genetic links to how we react to humor. In a 23andMe analysis of over a million people, one of the strongest links to how easily someone “gets” a joke showed up in a gene involved in brain development and also studied in autism research.
Other studies have looked at a serotonin-related gene variation called 5-HTTLPR and found that people with certain versions of it tend to smile and laugh more easily.
