The story has been in the mass media all over the world: First-born children are smarter (by 3 IQ points on average) than their younger siblings, and this is due to psycho-social rather than biological causes. The findings are based upon tests in 240,000 Norwegian young men.
Some of the blogs I read have commented on this. I agree with Clark Bartram who points out that a difference of two or three IQ points is completely meaningless for individuals. As far as I got it, this is also the opinion of the study authors. Janet D. Sternwedel comments the study from a parenting view and Suzanne E. Franks raises the question if results gained from men may be applied to women as well.
Large numbers make things different
If I undergo an IQ test today and get x points, it is very likely that I get x+3 or x-3 points a week later. Such tests never can be as accurate as physical measures, and my mind fitness will change from day to day. Therefore, if a study would tell me that I gain three IQ points, I just would shrug my shoulders and ask, so what?
But with two hundred thousand persons tested, things are quite different. The up and down deviations are nullified by the law of large numbers. A difference of 3 IQ points no longer is a matter of chance, but becomes significant if it is based upon a large number of tests.
What does it mean for individuals?
When statistics, based upon large numbers, has found an IQ difference of 3 points to be significant, for me, as an individual, this difference has gained no additional meaning. I still shrug my shoulders because I am not the average of two hundred thousand men.
The real point is not the IQ difference (which is meaningless) but the effect that is causing such a difference. If I understand this effect and if I manage to make best use of it, things may become meaningful.
It is self-teaching that matters
For me, birth order is quite irrelevant in this study. Not only is it a given fact that we cannot change, but the study itself came to the conclusion that only certain aspects of birth order play a role. If an elder sib dies, the IQ of the younger will rise, the study has found. Thus, it is not birth order but the social role in the family that has an influence on intelligence.
The main difference between firstborns and the rest is how they learn. Firstborns are pioneers who have to find their own way which may be hard but rewarding; the younger always have the example of the elder sibs that may guide them. Firstborns learn by teaching themselves and the younger ones - which seems to have a measurable effect on intelligence.
The message I get from this study is: Teach your kids how to think their own way, how to ask their own questions, how to find their own answers, and their IQ may rise by even more than three points.
Conflict of interest: I am a firstborn of seven siblings which may influence my view of this study.
Photo credit: flickr.com/photos/ericasimone/302288448/