Mozart was a child prodigy. He composed from the age of five, and at 17—an age at which many parents would be reluctant to entrust their son with the keys to the family car—Mozart was appointed a court musician in Salzburg.

Was his talent genetically determined or did he have the good fortune to be coached from an early age and did he acquire his musical genius through learning?

People can differ dramatically in their abilities and expertise: Some of us can play chess with 103 opponents simultaneously, scoring 102 wins and one draw, whereas others have difficulty winning a game of tic-tac-toe that they open. What explains this enormous variability?

One explanation dates back at least 150 years and is credited to Sir Francis Galton, who mused that “genius” arises from an innate, genetically determined, ability—after all, what else could explain why there were more than 20 eminent musicians in the Bach family?

An alternative explanation holds that “genius” or expertise is purely the result of training. The founder of behaviorism, John Watson, famously thought that he could turn any healthy infant at random and turn him into a doctor, lawyer, or artist. This strand of thinking has found its contemporary expression in the “deliberate practice” view of expertise pioneered and popularized by K. Anders Ericsson and colleagues. On this view, expertise and any manifestation of “talent” is the result of 10,000 hours of a certain type of intensive training, known as deliberate practice.

At first glance, these two views appear to be mutually exclusive: After all, it is tempting to dichotomize the world and assume that one is either born with innate musical talent or acquires it through practice, but not both. In actual fact, this dichotomous view overlooks the obvious possibility that both practice and innate talent contribute to determining one’s elite chess performance or musical talent.

A recent article in the Psychonomic Bulletin and Review by researchers David Z. Hambrick and Elliott Tucker-Drob sought to apportion the credit between “nature” (an innate genetic component) and “nurture” (the contribution from practice) in determining musical accomplishment.

Their study rested on the recognition that genes and the environment do not operate in isolation but are engaged in constant interplay. This interplay can take two forms: a gene-environment correlation (rGE) arise when people’s genes—rather than randomness—determine the type of environment they experience. For example, one’s motivation to practice chess rather than attend a party might be genetically determined. Another interplay takes the form of Gene × Environment interaction (G × E), which occurs when different environments amplify or diminish the effects of genetic variation. For example, engaging in deliberate practice may “unleash” otherwise dormant genes that determine one’s talent at chess.

Like many other studies addressing genetic questions, Hambrick and Tucker-Drob focused on the performance of twins: identical (monozygotic) twins share virtually their entire genetic material, whereas fraternal (dizygotic) twins share only 50% of their genetic material. The researchers analyzed an existing data base of 850 same-sex twin pairs who sat for a National Merit Scholarship test in 1962 as high school juniors. Given that all twins in this sample were reared together, greater similarity between the monozygotic twins than between the dizygotic twins would therefore reflect a genetic component.

Using a standard statistical model, Hambrick and Tucker-Drob were able to quantify the contribution of genetic variation and environmental factors to the twins’ musical accomplishment. It turned out that genetic variation accounted for 26% of the variance in accomplishment, with the remainder reflecting environmental variation (which in turn could be sub-divided, but this subtlety need not concern us here).

In other words, knowledge that a given twin was monozygotic would substantially reduce one’s uncertainty about the other twin’s performance compared to the case of a dizygotic twin. Clearly, musical accomplishment is at least in part determined by one’s genes, although the importance of practice cannot be ignored.

The two forms of interplay between the environment and genes are arguably of even greater interest.

First, Hambrick and Tucker-Drob found that the genetic effects on music practice (an rGE interplay) were even stronger than those on accomplishment: 38% of the variance in music practice was genetically determined. This is a striking result because conventionally, practice is considered to be an “environmental” variable: The essence of the deliberate-practice view (and indeed of behaviourism) is that learning and practice are causal elements of performance—they are, but it appears that one’s genetic make-up is a major factor determining how much practice one is prepared to invest. One possible explanation for this finding is that talent is rewarding, whereas a lack of aptitude makes practice too painful to continue.

Second, Hambrick and Tucker-Drob found that practice magnified—rather than attenuated—the genetic effects on music accomplishment (G × E interplay). In other words, genetic potentials for musical accomplishment were fostered and unleashed by practice, thereby further amplifying the role of genetic variation.

Does this then mean that one’s success is largely genetically determined, and for some of us practice may be a waste of time? Not at all: First of all, while there may be a substantial genetic component to our musical attainment, environmental factors also explain a large share of the variance. And perhaps more important, as Hambrick and Tucker-Drob note, the results indicate that “… children who do not engage in training or practice in music may have hidden talents, or at the very least potentials for talent, that go unrecognized and unrealized.”

So ultimately, practice is still key.