In More Behavioral Genetic Facts, I have expanded on an analysis on the meta-analysis of the heritability of criminality. This meta-analysis, a seminal work, represents the single best treatment of what we know of the genetic and environmental impact on criminality to date. Their all-inclusive analysis, combining children and adults, self-report, parent report, and criminal records together, seemed to produce a small shared environment estimate of 0.16. This dropped to 0.09 in adults. However, as the gist of the post illustrated, and as any veteran of behavioral genetics knows, methods matter. Studies on children often produce a transient effect of the shared environment. Self-report tends to be highly noisy. Parental report is often quite biased. As I noted there:
Rating method a2 d2 c2 e2 Total no. of pairs in category Self-report 0.39 – 0.06 0.55 13,329 Other report (usually parents) 0.53 – 0.22 0.25 6,851 Criminal records 0.33 0.42 – 0.25 34,122
The total, or broad-sense heritability, H2 , is the sum of the additive (the narrow-sense heritability) and the non-additive genetic components. As we can see, when actual criminal records (a semi-objective metric) are used, as we’ve seen, the heritability shoots up to the usual range, at 0.75, and the shared environment estimate vanishes. The criminal record analysis also captures the largest number of subjects, bolstering its reliability.
(For the record, the countries spanned by the studies in the meta-analysis include the U.S., Canada, the U.K., Australia, Denmark, and Sweden.)
This (along with the other studies discussed there and previously) should end the argument on the effect of parents to influence the course of their children’s lives. “Good” parenting simply can’t rescue the genetically predisposed from delinquency, and neither can “bad” parenting (provided it’s not too extremely so) hold back the genetically gifted. These should serve as final nails in the coffin for the case for the efficacy of parenting. There is simply no more to debate.
In my post More Maps of the American Nations, I have made substantial additions. I have added local-level breakdowns for support for same-sex marriage, abortion, and gun ownership. As well, I break down national suicide rates by county by race.
Go there for more on this matter.
Additionally, while this has not been added to any posts, I wanted to comment on another recent find. This one is on the topic of obesity. I recently found a meta-analysis of randomized controlled trials (RCTs) of diets for the intent of weight loss. With a combined N > 60,000 and a study duration of 2.5 – 10 years, it found that diet was completely ineffective for weight loss. The subjects showed no aggregate permanent weight loss at the end of the study period. It also showed that there was no effective improvement in health outcomes nor were there fewer deaths during the study period for those in the treatment groups. Diets don’t work!
In reporting this, one objection that I’ve encountered is that the diets used in the study were traditional low-fat or low-calorie types, and not the purportedly superior “low-carb” diets. However, this has also been studied. A meta-analysis of RCTs found that low-carb diets don’t work much better:
Combined N: 712
Duration: 1-2 years
Total average weight lost with low-carb diets at study end: 8 lbs!
Obesity remains impossible to effectively treat without surgical intervention. Unfortunately, this matter is clouded by wishful thinking and flat out irrational thought. People recount success stories – indeed, there are studies tabulating those that have successful lost weight and kept it off. However, the belies the enormous amount of selection bias involved in collecting these “success” stories. Proponents of the practical feasibility of long-term weight loss collect all the hits and discount the orders of magnitude greater number of misses. It’s often easy to get success if one cherry-picks enough. But so many are simply unable to see that.
As for that matter of surgical intervention: one can successfully treat obesity on a long-term basis with bariatric surgery. One might imagine that this speaks to the intrinsic danger of excess body weight. However, a meta-analysis of clinical trials – NOT randomized – found questionable results on that front. Improvements in health and lifespan were small and often not significant. Indeed there was a consistent pattern: the larger studies produced weaker results, indicating that publication bias is likely in play. This is in addition to the fact that the selection for treatment was not random. There are many criteria doctors place on who receives bariatric surgery, and it’s almost a given that the decisions to perform surgery were biased to their healthier patients.
The causes and nature of obesity remain a mystery, but we won’t make much progress if we stick to invalidated models, which foolishly stress blame and “personal responsibility.”