Category Archives: IQ

Genetic Influences on the Overlap Between Low IQ and Antisocial Behavior in Young Children

Genetic Influences on the Overlap Between Low IQ and Antisocial Behavior in Young Children

The well-documented relation between the phenotypes of low IQ and childhood antisocial behavior could be explained by either common genetic influences or environmental influences. These competing explanations were examined through use of the Environmental Risk Longitudinal Twin Study 1994–1995 cohort (Moffitt & the E-Risk Study Team, 2002) of 1,116 twin pairs and their families. Children’s IQ was assessed via individual testing at age 5 years. Mothers and teachers reported on children’s antisocial behavior at ages 5 and 7 years. Low IQ was related to antisocial behavior at age 5 years and predicted relatively higher antisocial behavior scores at age 7 years when antisocial behavior at age 5 years was controlled. This association was significantly stronger among boys than among girls. Genetic influences common to both phenotypes explained 100% of the low IQ–antisocial behavior relation in boys. Findings suggest that specific candidate genes and neurobiological processes should be tested in relation to both phenotypes.

Remembering the outrage the last time I posted material of this nature, I shall stick to snipping the more interesting bits of text out and not add my own comments.

The exclusion of children who received a diagnosis of ADHD had no effect on our findings regarding the gender difference in the strength of the association between low IQ and antisocial behavior.

 Furthermore, it is important to note that once children with ADHD diagnoses were excluded from the sample, the low IQ–antisocial behavior correlation in girls was attenuated to almost nonsignificance. These findings suggest that the low IQ–antisocial behavior relation in girls is largely an artifact of comorbid ADHD.

The population prevalence of early-onset antisocial behavior that is life-course persistent is low (5% among men, less than 1% among women); however, these individuals account for more than their share of crime (Robins, 1966). Low IQ predicts the chronicity of antisocial behavior (Lahey et al., 1995); therefore, the children in our study who are boys, have low IQs, and have high levels of early antisocial behavior are at high risk for becoming life-course persistent antisocial individuals. This antisocial subtype is at the highest risk for myriad negative outcomes in adulthood, including mental health problems, substance dependence, financial problems, drug-related violent crime, and violence against women and children (Moffitt, Caspi, Harrington, & Milne, 2002). Genetic influences on IQ and antisocial behavior suggest that the parents of these vulnerable children are also likely to have low IQ and to be antisocial. Such parents are at risk for creating family environments that aggravate rather than ameliorate their children’s vulnerabilities. Thus, the families of young boys with low IQ who exhibit high levels of antisocial behavior should be targeted for early intervention.

One of the pieces of info I picked up from this was that … The prevalence of this research diagnosis of ADHD was 8% (70% boys; 30% girls). Also that the genders scored the same for IQ. I can’t help wondering if the abscence of these lower IQ antisocial boys from school during their teen years might not be part of the reason for the occasional finds of slightly higher IQ’s in the boys- the misssing lower IQ males boost the male average (tucked away in specialist schools, or just absent due to truancy or abandoning school at an early age.

IQ Population Genetics: It’s not as Simple as You Think

IQ Population Genetics: It’s not as Simple as You Think

A paper I came across while blog surfing. While the IQ stuff is interesting, what really caught my attention was the section on the out of Africa date.

Both genetic evidence (Ingman et al., 2000; Underhill et al., 2001; Zhivotovsky et al., 2003) and the fossil record (White et al., 2003) point to Africa as the likely homeland of our species. According to the most widely accepted scenario, one or more subgroups of early modern humans left Africa between 120,000 and 100,000 years ago to become the ancestors of the non- African populations

Which makes a pleasant change after reading an idiot paper earlier today that was hitting the 40k date. Again.

 And something I didn’t know..

Genes, like drugs, have many side effects. This is called pleiotropy. For example, the average IQ of nearsighted people is 6 to 8 points higher than the average for normal-sighted people.

Although I am familiar with a medical condition called torsion dystonia that raises the IQ of the sufferer by an average of 10 points. An interesting read.

Intelligence and birth order in boys and girls

Intelligence and birth order in boys and girls

 The relation between intelligence and birth order was shown in a recent publication [Bjerkedal, T., Kristensen, P., Skjeret, G. A. & Brevik, J. I. (2007). Intelligence test scores and birth order among young Norwegian men (conscripts) analyzed within and between families. Intelligence, 35, 503–514] to be negative. Subjects in this and in an influential earlier study [Belmont, L. & Marolla F. A. (1973). Birth order, family size, and intelligence. Science, 182, 1096–1101] were all men. We tested if the association of IQ and birth order is the same in men and women. Longitudinal IQ data were available from 626 Dutch twin pairs at ages 5, 12 and 18 years. The number of older siblings in these twin families was between zero and five, and was recoded into 3 categories (0, 1 and 2, or more). IQ data were analyzed with a model in which age cohort, number of older sibs, sex and all interactions were included as fixed effects. The dependency between twins was modeled as a function of additive genetic effects (A) and common environment (C) shared by children from the same family. Effects of A, C and unique environment (E) were allowed to differ as a function of age. The correlation across time between IQ scores was modeled a function of genetic and environmental factors. The test for the effect of N of older sibs was significant [F(2,827)=6.51 (p=0.0016)], while the interaction of N of older sibs with sex was not significant [F(2,933)=1.93, p=0.15]. Heritability for IQ was estimated at 37% at age 5 (C explained 34% of the variance). At ages 12 and 18 heritability for IQ was 81% and 82%, respectively. At these ages C did not contribute to IQ variation. We conclude that the dependency of IQ scores on birth order does not differ for boys and girls. We discuss these results in the context of the general findings of the absence of common environmental influences on IQ scores in the genetic analyses of adolescent and adult twin data.

On the quite I’m quite interested in IQ testing and studies. This has some information on the Hereditability on IQ with age; 37% at age 5, 82% at age 18. And as I recall it gets higher the older you get, in the 90% once you are a full adult living your own life. Which makes a lot of the IQ studies that have been carried out on children pretty much pointless, as their IQ’s are so plastic at that age.

Are you smarter than a chimp?

There’s a chimp called Ayamu that is absolutly ace at this memory game. You can play the game yourself. It took me a few tries before I got the hang of it. The trick is to relax, see the whole screen and not think. So now I am offically at least a match for chimp intelligence.

You have got to watch the vid of her doing it, it’s amazing!

IQ and gender.

Hmm I’ve been reading up on IQ and gender on Wikipedia. Pretty funny really. If you know a lot about IQ tests and life outcome, it’s laughably simple to see how some of the mooks of this world will read SAT scores and university IQ tests as proof that women have a lower IQ, as the male average on all of these is a bit higher than female. The reason for the higher score is…drumr0ll… That most of the really low IQ people won’t be taking those test, and they are mostly men!It’s very simple, the lower the IQ, the more likely you are to drop out of school and not get around to sitting an exam that you know you’ll fail abysmally. If your IQ is less than 70 there is a 55% chance that you’ll drop out of high school, at 80 to 70 it’s 35%, at IQs above 120 it’s statistically insignificant (just me then). And the majority people with learning difficulties are male (about twice the number of women). It skews the numbers to make male IQ look higher. If you want to test a population to find the mean, you have to test ALL OF THEM. Anyone who understands statistics even a bit can see the bias.