Here’s the simplest personality test you’ll ever take. It consists of a single question:
Of your siblings, are you the oldest child, second oldest, third oldest… or perhaps the youngest?
For more than 100 years, psychologists have debated the relationship between birth order and personality. You’ve probably heard of “middle-child syndrome”. It’s the idea that the middle child misses out on both the privileges given to the oldest child and the allowances made for the baby of the family, and this may explain why they become withdrawn or resentful.
Firstborns are often thought to care more about pleasing their parents, and to be conscientious and dominant, with laterborns being more easy-going, sociable and creative.
However, 2015 saw the publication of two very large studies looking at almost 400,000 people overall, which showed that these claims are largely myths. Although firstborns did emerge as fractionally more conscientious and less sociable than laterborns, they bucked the expected trend by coming out as more agreeable and less neurotic. More importantly, the size of this effect was tiny, with birth order explaining well under 1% of variability between different people with regard to personality.
The lesson is clear: whatever your strengths and weaknesses in terms of personality and intelligence, your position relative to your siblings is almost certainly not to blame.
A fully referenced version of this article is available at benambridge.com. Order Psy-Q by Ben Ambridge (Profile Books, £8.99) for £6.99 at bookshop.theguardian.com
