Does Having A Brother Or Sister Influence Your Personality?

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Call up your brothers and sisters because a new study just dropped, asking the age-old question of whether siblings affect our personalities.

Researchers from the University of Wellington and the University of Zurich surveyed over 85,000 people across nine countries, including Australia, to find out whether growing up with a brother or sister affected your personality differently.

Given the amount of time we spend growing up around our siblings, it feels like they should have some impact on how we turn out. I grew up with an older brother and, let me tell you, so many of my interests and hobbies were directly influenced by him. Even my wardrobe was full of his hand-me-downs.

However, as scientists dug into this question, the data didn’t support this seemingly common anecdotal experience. But there are some pretty interesting suggestions as to why the study didn’t find a statistical link.

What Exactly Did The Study Show?

The biggest thing about this new study is, in fact, how big it is. Their final data set was over 85,000 people — which, according to the authors, is many times the size of earlier studies.

They also investigated more personality traits than previous studies, including the so-called ‘Big Five’. Known by the acronym CANOE or OCEAN, the five traits are conscientiousness, agreeableness, neuroticism, openness to experience, and extraversion. The Big Five is apparently the most widely accepted personality theory by psychologists today because the traits stay relatively stable throughout our lives, are influenced by both genes and environment, and are powerful predictors of our behaviour.

The study also investigated traits of risk tolerance, trust, patience, focus of control, and typical female personality index. 

And even though study didn’t find a statistically significant relationship between personality and siblings, the researchers suggest some interesting reasons why we might still feel like there is a link. 

Why Doesn’t Sibling Gender Affect Personality?

Researchers suggest that the link between personality and siblings in different families could average out to a net zero. So, say for example, the link could be really strong in certain families and non-existent in others, resulting in no overall effects.

There’s also a thing called publication bias, where the results of a study can affect whether something gets published or not. So depending on what gets published, it could lead to a cycle of conflicting results. This is what researchers Rodica Damian and Brent Roberts think happened with all the previous conflicting research about personality and birth order.

There’s also been conflicting results about the link between personality and gender. If personality and gender aren’t strongly linked in the first place, then it makes sense that our sibling’s gender isn’t strongly linked with our personalities either.

Does Sibling Gender Affect Anything?

There are, however, other findings that suggest that sibling gender does affect ‘life outcomes’ — things that happen in our lives.

There was one study in the US which showed that some women with brothers tend to earn less money than those without. And another study in South Asia found that some women with younger sisters got married earlier and those with older sisters married later.

The actual mechanisms behind why this effect is seen could be psychological, sociological, or economic. But we don’t really know, and it’s hard to replicate taking into account generational and geographical distances. What we do know is that while there does seem to be some interesting sibling dynamics that affect our lives, it probably doesn’t affect our actual personalities in a consistent way.