Playing Mozart to babies makes them smarter

What actually happened

Rauscher, Shaw, and Ky published a one-page Nature paper in 1993. Thirty-six undergraduates performed slightly better on a paper-folding task after listening to a Mozart sonata, for roughly a quarter of an hour. The authors made no claim about babies, no claim about permanent intelligence, and Rauscher spent years afterward saying so.

It escaped anyway. Don Campbell's 1997 book trademarked "The Mozart Effect," and the claim mutated into permanent infant IQ gains. Governor Zell Miller budgeted state funds in 1998 to give every Georgia newborn a classical CD, and Florida legislated classical music in state-funded daycares. Public policy, built on 36 undergraduates and a paper-folding test.

The demolition came in stages. Chabris' 1999 meta-analysis found the effect negligible. Steele and colleagues failed to replicate it. Pietschnig's 2010 meta-analysis in Intelligence, covering 39 studies, found nothing, and noted that studies from labs affiliated with the original authors reported larger effects than independent ones. The most likely explanation for the small original result is arousal and mood: anything you enjoy improves short-term performance slightly, and a Stephen King audiobook worked just as well in one study. Learning an instrument, as opposed to passively hearing one, does show real associations, which is a different and better-supported claim.