You've gotta be careful with Wiki at times. In that same paragraph you'll also see the sentence "Contrary to popular[citation needed] belief, two parents of hig

You've gotta be careful with Wiki at times. In that same paragraph you'll also see the sentence "Contrary to popular[citation needed] belief, two parents of higher IQ will not necessarily produce offspring of equal or higher intelligence. In fact, according to the concept of regression toward the mean, parents whose IQ is at either extreme are more likely to produce offspring with IQ closer to the mean (or average)." That literally made me laugh. Whoever wrote that has no absolutely clue what regression towards the mean is or means, yet felt qualified to write on it. The reason Wiki is useful is as a collection of sources to meaningful information and statistics. But much of what is written by Wikipedia editors themselves is often very bad, and exponentially more so when you enter into any area that could be in any way controversial -- which includes this topic. It should be taken with a grain of salt. In this case, however, the statement you mention is technically correct. But one thing you have to account for is that 20% encompasses all environmental differences. Put another way, if we all had a 100% identical upbringing and environmental factors then the heritability of any given observation would obviously be 100%, since any deviations from the norm would be primarily due to genetic factors. So that means that all of the wild variations in our upbringings and backgrounds are constrained to as little as 20% of any variation in IQ.