Intelligence is Inherited 79
codeButcher writes: "Now you can blame it on your parents! NewScientist.com reports on a study done on twins, that determines that IQ [and lack thereof then too, I suppose] is inherited. Quote: The finding suggests that environment - their own personal experiences, what they learned in life, who they knew - played a negligible role in shaping it."
This isn't news, and it isn't the whole story (Score:4, Informative)
The nature nurture debate has raged for centuries in respect to intelligence. Ever since Darwin's cousin Francis Galton proposed his theories of hereditary intelligence.
At first glance, it seems neat that these guys did a study on twins. You might think, "wow, what a great approach." You'd be right, then you'd hopefully realize that other people had these ideas in the past, and they did the right studies and came to the right conclusions.
When Thomas Bouchard [umn.edu] was in charge of the Minnesota Twin Studies, he and his colleagues compared twins raised together and apart.
Bouchard and colleagues tested 56 pairs of monozygotic (identical) twins who had been raised apart and compared them to hundreds of identical twins who had been reared together. The twins were tested on dozens of capacities. This approach allowed them to examine spatial ability, verbal ability, mathematical ability, personality, etc. Rather than the antiquated "g" or general intelligence factor.
So, here's a study with many more subjects, much better comparisons, and more detailed data. Here's the cool part: if you correlate the scores of twins on the Wechsler Adult Intelligence Scale (WAIS) (the standard IQ test in the US) and Ravens Progressive Matrices (An allegedly culturally unbiased test of reasoning skills), you see a 65% (WAIS) or 50% (Raven's) agreement among scores of twins raised together, and among twins raised apart, the WAIS scores are about 35% in agreement with nearly the same 50% agreement on Raven's scores.
What does this mean? Well, it means that even in the best cases, IQ scores are about 50% hereditary. In addition, the big drop off between WAIS scores indicates that environment has an important role in intelligence. Given that most of the twins were raised in similar middle class families (who adopt kids), the estimates of the role of environment are probably inflated.
That being said, the study mentioned in the story focuses primarily on brain structures. This pisses me off. One of the lamest things about current cognitive neuroscience is the common misunderstanding of the difference between structure and process. Given the little we know about how the brain works (yeah, we're getting good info about the molecular level, and we know in general what larger regions like Broca's area are responsible for, but we have woefully little info about how these structures actually work), idiot PR people take brain findings and blow them out of proportion.
The fact is, if you want to talk about intelligence, you have to talk about behavioral measurements. Looking at structures can, at best, tell you if something is wrong. So, yeah big deal, major structures are heritable, given the fact that environment has been shown in better studies to play a key role in intelligence, we shouldn't rely too much on these findings.
Bottom line: Yes of course nature plays an important role in intelligence. You'd have to be an idiot not to realize that. This study is not groundbreaking. Moreover, the headline of the article is sensationalistic and only a half-truth. Environment does play a role in intelligence. My god, meet a person who ate lead paint as a kid and you'll realize that.