Is the eldest sibling really smarter?

A recent study at Leipzig University has confirmed that birth order and IQ are related, and in particular, that firstborns have a higher IQ than their younger siblings.

The study was carried out to address a question psychologists have been arguing about since 1874, when the British scientist Francis Galton collected information on a number of English scientists and found that most of them were first born sons. As a result, he concluded that the eldest child in the family is likely to do best intellectually. Galton thought this was because parents are able to offer their first born child exclusive attention and rich linguistic input during the period when language is emerging and the brain is developing most rapidly.

Since that time, a number of researchers have tried to prove whether Galton was right. However, the studies to date have been too small for anyone to feel certain that the findings reflect what’s happening in the population generally. The Leipzig study, on the other hand, is based on a huge amount of data. The researchers pooled information from a number of studies conducted in three countries — the US, the UK and Germany - and examined data from 20,186 individuals ranging in age from 18 to 98 years.

The IQ difference they found isn’t large — firstborns scored on average 1.5 points higher than second-borns — but it occurred significantly more often than would be expected by chance. We can, therefore, feel confident that the conclusion is robust. Firstborns really are likely to have a higher IQ than their siblings.

But wait. Is it justifiable to conclude, as many have done, that therefore firstborns are more intelligent than their siblings? I don’t think so.

The first thing to point out is that IQ is not the same as intelligence. IQ is a limited measure. It depends heavily on good language skills, basic arithmetic and general knowledge, the skills most needed to obtain high marks in exams. As such, it’s a good predictor of academic success at school. It tells us little else.

Intelligence, on the other hand, is much more complex. It is the ability to perceive information, to make sense of it and store it as knowledge, and to have the capacity to apply it in ways that are useful to and/or valued by oneself and others. A person can express intelligence through music, art, dance, or sensitivity to other people, as well as through the more strictly academic routes such as language, maths or science.

Each child in any family hopes to be recognised as special and different from their siblings. Because firstborns receive so much language input from their parents and are therefore likely to become accomplished in that way, it’s only sensible for later born children to choose a different area — music, sport, or art, for example — in which to excel. I would therefore argue that each child in a family is intelligent just in different ways.