Takao Hensch, professor of molecular and cellular biology at Harvard University, believes that absolute pitch — the ability to identify or sing a specific note without any reference points — is a learned ability, normally only acquirable by humans in a "critical period" early in our lives. In the past, Hensch and other scientists believed, if we missed the window and hadn't gained the ability to pick out or produce a note at will by the time we were around seven years old, we wouldn't ever be able to master the skill as adults.

But a new study co-authored by Hensch claims that a drug gives humans the ability to learn perfect pitch, long after that critical period has closed. Hensch says that when applied to a group of test subjects, valproate — a mood stabilizer more commonly used to treat epilepsy — returned the brain's plasticity to a "juvenile state," allowing it to learn skills it should be too old for.

Research had previously shown that adult mice given histone-deacetylase inhibiting drugs (HDAC inhibitors) could "establish perceptual preferences that are otherwise impossible to acquire after youth." To test whether this connection also existed in humans, Valproate, another HDAC inhibitor, was given to a group of healthy young men with no musical training. The men were then asked to perform a set of exercises for two weeks with the aim of improving their pitch while another control group was asked to perform the same exercises, but given a placebo.

According to the study, those subjects given valproate learned to identify pitch "significantly better than those taking the placebo." Hensch calls the results remarkable, telling NPR that until now there had been "no known reports of adults acquiring absolute pitch." The implications of the study aren't limited to learning how to sing beautifully: by altering brain plasticity, users of valproate could conceivably learn other skills normally picked up during the early critical period. Hensch picks out language learning as an obvious area of application for the drug.

But he also cautions against its widespread use before the neuroscience behind it is understood. "Critical periods," the professor says, "have evolved for a reason." By reopening the critical period, Hensch says we may run the risk of erasing the identities we've shaped by the way we were raised, accidentally replacing important portions of our personalities.