Infants have super-charged hearing, but scientists didn't know quite how amazing it was until 2001, when an experiment tested their ability to listen to multiple frequencies at once. The experimenters tested 73 infants ages 7 to 9 months old by exposing them to four half-second bursts of a computer-generated 1000-hertz tone and a 1000-hertz broadband noise that sounded like telephone dial tone or static. Sometimes the tone or the noise was played alone and sometimes the sounds were masked with background noise. They watched as the babies turned their heads toward the sound. The findings? While adults and kids 10 and over hone in on one frequency, the experimenters found that babies listen to all frequencies simultaneously, which is why they recommend to reduce background noise when reading or interacting with a little one.