Why can almost no adult learn to name a note just by hearing it?

The leading explanation is a critical period: absolute pitch, the ability to name or re-create a note with no reference tone, might be learnable by anyone during a window of auditory development, after which the brain's strategies favor judging notes relative to one another. Adults who try later are working against that shift, and for a long time none succeeded: as of 2005, no adult had been documented acquiring the skill, because every adult formally tested after training fell short of the accuracy of lifelong possessors.

The idea is borrowed from biology, where a critical period is a set window in which an organism must acquire a skill or never acquire it later. Researchers who back it agree that absolute pitch depends on learning, but not on how: does training during the window create the skill, or does a lack of training let relative pitch overwhelm the absolute kind?

The adult story has recently shifted. In 2013, adult men who took valproate, an anti-seizure drug, learned to identify pitch significantly better than men on a placebo, which the experimenters took as evidence the drug facilitated critical-period learning in the adult brain. And a 2019 study reported two of six adult participants reaching accuracy and response times statistically indistinguishable from confirmed lifelong possessors, findings independently replicated since. The window may be stubborn rather than fully shut.