Suckiologists III: A genetic twin study on impulsivity (and other traits) by Eaves, Martin, and Eysenck was published in 1977 which showed very small shared environmental effects. Loehlin et al. (1987) reported zero shared environmental influence for impulsivity in a study of adoptees. A Swedish study (1988) found that the correlation for identical twins raised together was almost the same as that for identical twins raised in separate families indicating no effect of shared environment.

These methodologically powerful studies persuaded sociologists in the early 90's to drop their interest in the role of parenting in causing impulsivity.

Oh I'm sorry, in 1990, sociology started for the first time in forty years to focus on disciplinary styles. Sociologist Travis Hirschi and his colleague Michael Gottfredson published a book called A General Theory of Crime. In it the authors claimed that all crime is caused by a failure to punish children when they behave badly. Permissive parents raise kids who never learn to check their impulses and end up as career criminals. The theory is so powerful, the authors said, it even explains white-collar and organized crime.

Then, in 1998, the world of social science was rocked with Judith Rich Harris' The Nurture Assumption. She echoed these earlier studies--and many, many others--that pointed away from parental influence, and she suggested that peer influence was important instead. Sociological criminology naturally followed suit by turning its attention to peer influence.

Oh, I'm sorry, what actually happened is that Hirschi and Gottfredson's "self-control" theory went red hot and quickly became a leading criminological theory. Peer influence was so 80's. So now scads of studies are coming out showing a correlation between erratic parenting, impulsivity, and crime. Do they investigate the possibility that the correlation is due to genes? (I mean, broad heritability is .4 or.5, after all.) Of course not, only racist Neanderthals do that (when they're not opposing Obama).

Sociologists are classic examples of academic SWPL-hood. Their discipline is driven by fads. People jump at a new idea, get tired of it, and then jump to the next thing. Data has little to do with it. What a friggin' joke.