Genetics of Personality
Tom McMahon of Kid Tips wrote on Sunday:
Our genetic influence is responsible for 40 percent to 50 percent of our individual variations in personality traits.
The home environment and parental and sibling influences altogether account for less than 10 percent.
He quotes a 1987 finding that two children from the same family are as similar in personality as any other two children selected randomly from the population.
Does that make any sense? If genes determine at least half of our personality and genes are inherited, we’d expect that siblings would share more characteristics than two random people. The commonalities would be even more pronounced after taking into account other shared environmental factors like parenting, schooling, etc.
That said, my sister and I are very different people. It sometimes even seems that our friends have more in common with us than we do with each other. But our bond as sisters with shared childhood experiences is unrivaled by anything else, including genetics.
For more information on genetics and the family, see Genetics of Family Interaction.
How curious. So he’s basically trying to back up his assertion with evidence that contradicts what he’s saying. If I had more time this afternoon I would try and look up the 1987 study and see if maybe he’s leaving something out, like that they were unrelated adopted children raised in the same home (which would support what he’s saying).
Always interesting to see all the misinformation that’s out there. Thanks Lei!
Brad, If I weren’t on vacation, I’d go do some more digging around too, but as it is, most people reading his column probably take it at face value.
Where’s the other 40%-50% which has an influence as well? Perhaps that’s why he concluded 2 randomly selected people are as equal as 2 brothers/sisters.
Not sure whether that is the assumption which has been taken and besides that if it is, how it is backed up.
What is obvious though is that genes indeed do not determine the entire personality of people. In normal brother/sister relations you can already see this, but you can see this even more clearly in twins, triplets, etc. In some occasions they are pretty much the same, but I also know an identical triplet in example which when it comes to personality are 3 absolutely different people.
Stef, Thanks for the comment. Non-genetic/heritable factors that go into determining people’s personalities can pretty much be anything that they encounter in daily life. It’s a complex topic that an advice column like the one mentioned in this post is unable to address completely.
I THINK THIS STUFF IS CRAP THERE ARE SO MANY OTHER PERCENTAGES OUT THERE THAT ARE COMPLETELY DIFFERENT THAN THIS. WHERE ARE YOU GETTING YOUR NUMBERS FROM THATS WHAT I WANT TO KNOW.
Billy at beersogood@hotmail.com, Maybe you should redirect your question to Tom McMahon of Kid Tips.