I’m sure many have heard the story of László Polgár, who purportedly raised his three daughters, Zsuzsa, Zsófia, and Judit, to become chess masters, with Judit Pulgar, the most successful of the three, becoming the greatest female chess player in the world. This story is often retold as evidence that child prodigies and geniuses are made, not born.
Polgár studied intelligence when he was a university student. He later recalled that “when I looked at the life stories of geniuses” during his student years, “I found the same thing….They all started at a very young age and studied intensively.” He prepared for fatherhood prior to marriage, reported People Magazine in 1987, by studying the biographies of 400 great intellectuals, from Socrates to Einstein. He concluded that if he took the right approach to child-rearing, he could turn “any healthy newborn” into “a genius.” In 1992, Polgár told the Washington Post: “A genius is not born but is educated and trained….When a child is born healthy, it is a potential genius.”
The experiment began in 1970 “with a simple premise: that any child has the innate capacity to become a genius in any chosen field, as long as education starts before their third birthday and they begin to specialise at six.” Polgár “battled Hungarian authorities for permission” to home-school the girls. “We didn’t go to school, which was very unusual at the time,” Judit recalled in 2008. “People would say, ‘The parents are destroying them, they have to work all day, they have no childhood’. I became defensive, and not very sociable.”
Polgár’s daughters all became excellent chess players, but Sophia, the least successful of the three, who became the sixth-best woman player in the world, quit playing and went on to study painting and interior design and to focus on being a housewife and mother. Judit has been described as “without a doubt, the best woman chess player the world has ever seen.” As of 2008, she had been “the world’s highest ranked female chess player for nearly 20 years.” Susan, who became second-best woman in the world, was, at age 17, the first woman ever to qualify for what was then called the ‘Men’s World Championship’,[dubious – discuss] but the world chess federation, FIDE, would not allow her to participate.
This is what we should expect given the correlation of about r = 0.24 between IQ and chess ability (see also this analysis, although I disagree with the details). And the contrary claims – like the one that Bobby Fischer’s IQ was in the 180s – are less well-sourced (although Fischer was the son of a Hungarian-Jewish mathematician, so who knows?).
If it were possible to be a chess world champion with an IQ of 135, then maybe it’s possible to be a “mere” grandmaster with IQs in the high 120s and low 130s. And it’s just barely plausible that some sufficiently smart people might have three kids who all have IQs in the high 120s and low 130s.
The Polgar sisters likely had IQs in the 120-140 range. 
In singling out Polger, one exhibits the Texas sharpshooter fallacy that befalls Gladwell, Danienl Khaneman, Dan Ariely other pop psychology authors and behavior scientists, who gather as much data as possible to find anything possibly anomalous, but disregard the thousands of studies that show nothing. If you keep testing and looking, you’ll eventually get statically significant results, but many of these are just coincidences.
From the comments on Scott’s blog:
I think that the story of Laszlo Polgar and his daughters seems like an extreme case of survivorship bias. We don’t know what sample size we started out with. For every Laszlo Polgar who succeeded in creating geniuses, there may be 100 or 10,000 who did exactly the same thing and failed, for no reason other than the fact that the “Polgar Method” works 1/10,001 times. There probably aren’t wikipedia pages for all of the kids who played 48 hours a week of chess from age 4 onward but maxed out at a 1900 rating, became CPAs, and lived quiet lives in Evanston, Illinois.
The fact that the success of Lazlo Polger has not, as far as I know, been replicated is more reason to be skeptical that genius can be taught, and that these examples are so famous speak to their rarity. Science is the ability to reproduce results, not fawn over one-off anecdotes.
So are geniuses born or made? For highly g-loaded activities, it’s a virtual certainty the former, and that the Polgar sisters succeeded because of high IQ and other biological factors, with parenting perhaps a necessary but still insufficient condition. Had they not learned chess, they probably could have excelled at other areas.
For unknown reasons, people get offended by the fact that prodigies are born, not made. The ‘blank slate’ is one of those bad ideas that just refuses to die. People want to believe that everyone has equal instinct ‘worth’ and that differences in outcomes must be the result of external factors.
To understand why geniuses are born, according to studies, prodigies have superior working memory , which is a component of IQ necessary for learning and cannot be taught. Talking at the age of one and reading at the age of two is not the product of parenting but rather having a very high IQ. And the distribution of talking and reading age follows a normal distribution, and from these values IQ can be extrapolated. Because of such a distribution, ‘extreme’ IQ values (>170) can be derived without the pitfalls of using mental age conversion. If one out of a million children can read before the age of 2, that implies an IQ of 180-200. Given that all parents talk to their infants, only biological factors such as IQ can explain individual differences in the rate of language acquisition.
 From The Mind of the Prodigy
More striking is that every single prodigy scored off the charts in working memory — better than 99 percent of the general population. In fact, six out of the eight prodigies scored at the 99.9th percentile! Working memory isn’t solely the ability to memorize a string of digits. That’s short-term memory. Instead, working memory involves the ability to hold information in memory while being able to manipulate and process other incoming information. On the Stanford-Binet IQ test, working memory is measured in both the verbal and non-verbal domains and includes tasks such as processing sentences while having to remember the last word of each sentence, and recalling the location of blocks and numbers in the correct order in which they were presented.
Admittedly, it’s only a sample size of eight.
 As Scott noted, an IQ of 130 seems ‘low’ for such exceptional chess ability. Maybe chess isn’t as high of a G-loaded activity as, say, coding, writing, theoretical physics, or abstract math. Savants can recite numbers and dates easily, but their IQs are average. In the order of g-loading:
1. Math, writing, reading, coding
2. Chess, music, theater
3. Art (painting, drawing etc.), kinesthetic art
I suspect for activities that are less g-loaded, parenting plays a larger role.
Verbal ability, surprisingly, is even a stronger predictor of academic success and intelligence than mathematical ability:
The only really successful efforts to make use of part scores appear to be in the SAT and the GRE, where both a verbal and a quantitative score are given. The quantitative score was thought to be a better predictor in the physical sciences and engineering, and the verbal score to be a better predictor in the arts and humanities. The latest evidence tends to show that this is an oversimplification. The current findings indicate that quantitative ability is a good indicator of choice of field, but that verbal ability is a better predictor of grades, even in highly mathematical subjects. Also, contrary to popular impression, scientists and engineers are verbally superior to arts and humanities majors, as well as being mathematically superior. Possibly this erroneous impression is due to the scientist’s unwillingness to guess in the absence of data. He says nothing when he has nothing to say.