It's kind of amusing at times to see siblings who seem to be worlds apart when it comes to their personalities when they, in fact, share the very same set of folks, and genes for that matter. And more often, we have turned to the psychology of birth orders to try to answer this seemingly glaring glitch in procreation.
The more common stereotypes include associating the first-borns to traits such as being the leader type, overachievers, and responsible; the middle children as the social butterfly, peacekeepers, and could be rebellious; and the youngest child as easygoing, attention-seekers, and could be a bit persuasive.
In a recent study, however, conducted by German researchers, findings reveal that there isn't much correlation between a person's personality and birth order. The results of the study, which is based on a huge dataset composed of 20,000 people from three different nationalities, was published Monday in the journal "Proceedings of the National Academy of Sciences."
The researchers conclude that there is no basis to support some popular theories claiming that birth order has something to do when it comes to an individual's extraversion, emotional stability, agreeableness, conscientiousness, or imagination. It shows that personality development is not determined by one's role in the family of origin.
The findings reveal, however, that the eldest among the siblings is more likely to have higher IQ. After considering a dataset from 5,240 Americans, 4,489 British people, and 10,457 Germans, findings show that first-borns were more likely to have a richer vocabulary, and researchers confirmed a small decline in intelligence for younger siblings, as noted by the Independent.
Julia Rohrer of Leipzig University, who is also co-author of the study, said the impact of birth order on the IQ of siblings, as confirmed by the results, could be the effect of social factors rather than biological, says one article from ABC News. One theory is that the resources of the parents tend to get diluted as the number of children increases. This could include attention, which the first-borns get to enjoy for a certain period of time without having to share.
Another factor, according to Rohrer, is that first-borns get to teach their younger siblings about how the world works. "Teaching other people has high cognitive demands. The children need to recall their own knowledge, structure it and think of a good way to explain it, which could be a boost to intelligence for some firstborns," she said.