Birth order has been blamed for everything from intellect to narcissism to compassion. Sigmund Freud (a first born) might be smarter, but he gets all worked up about losing the attention of his mother. Arnold Schwarzenegger (a number 2) feels inferior and tries extra hard to win the approval of his father by lifting a lot of weights. And third borns naturally have an inferiority complex, unless you’re Napoleon (a fourth born), in which case you have a Napoleon complex and compensate by conquering Europe.
Unsurprisingly, science has something to say about all of this. German researchers studied over 20,000 family panels for psychometric intelligence (that’s “IQ” to non-German researchers) and the Big 5 personality traits: extraversion, neuroticism, agreeableness, conscientiousness, and openness to experience. And science says … first borns really are smarter! By one-and-a-half IQ points and, no first borns, that’s not a significant enough difference to lord over your siblings. As for the Big 5, the researchers couldn’t find any support for birth order-related personality effects of any stripe. Given the size of the study, even Napoleon couldn’t challenge the results.
So, while your children are fighting their way through childhood, you can rest assured that no long-term damage is being done to their psyche just because one is older than the other. The long-term damage comes when the older one give the younger one a swirlie.