Social and economic circumstances do not explain why twins have significantly lower IQ in childhood than single-born children, according to a study in this week's BMJ.
Researchers studied 9,832 single-born children and 236 twins born in Aberdeen, Scotland between 1950 and 1956, using a previous child development survey as a base. They also gathered further information on mother's age at delivery, birth weight, at what stage of the child's gestation they were born, their father's occupational social class, and information on other siblings.
They found that at age seven, the average IQ score for twins was 5.3 points lower than that for single-born children of the same family, and 6.0 points lower at age nine.
The study also showed that taking into account factors such as the child's sex, mother's age, and number of older siblings made little difference to the IQ gap.
Despite advances in recent years in obstetric practice and neonatal care, the authors argue that the likely explanation is because some twins have a shorter length of time in the womb than other children and are prone to impaired fetal growth.
I've been expecting this finding for years. It makes perfect sense. Mom can't feed two fetuses as well as she can feed one. I wonder if diet and perhaps exercise could at least partially compensate for this effect.
I also wonder if the use of drugs to prolong pregnancy could raise average IQ. If pregnancies could be stretched out a few extra weeks would the resulting babies grow up to be smarter? Anything that could raise average IQ a few points would do more to boost economic growth and lower social pathologies than increased educational spending or the other typical liberal or free market libertarian nostrums.
Another point: IVF therapies ought to be aimed to reduce the odds of multiple fetus pregnancies. Each baby is going to pay a steep cognitive cost from not being the sole pregnancy.
By Randall Parker at 2005 November 29 10:41 PM Brain Development | TrackBackI would look to potential instances of mother-fetus competition for probable techniques for boosting IQ/health in vitro.
http://www.ulm.edu/~palmer/Mother.htm
Haw Ha! - Stoopid Twins!!
(course if they are hot I lose 50 IQ points lookin at them)
A difference of 6 IQ points isn't necessarily noticable when dealing with individuals (group differences are another story).
Modern IVF practice is tending more and more towards single-blastocyst implantation (my wife and I are currently going through the IVF pipeline, so we're paying attention to this field just now) -- the odds of successful delivery just don't improve significantly with multiple implantation, is my understanding.
Modern IVF practice is tending more and more towards single-blastocyst implantation (my wife and I are currently going through the IVF pipeline, so we're paying attention to this field just now) -- the odds of successful delivery just don't improve significantly with multiple implantation, is my understanding.