Mothers, if you feel like your teenager just hears blah blah blah when you’re speaking—rest assured, there’s a scientific reason for it.

A new study from Stanford Medical School found that around the age of 13, children no longer find their mothers’ voices “uniquely rewarding.” (The study, alas, did not comment on fathers’ voices.) Once children reach adolescence, the part of their brain that rewards stimuli showed increased activity for unfamiliar voices compared to a mother’s voice.

The finding adds to an earlier study by the same team, which found that preadolescent children did find their mother’s voice uniquely rewarding. When they hear it, several different parts of the brain, including reward centers, emotional processing, and visual processing, light up. However, brains shift as children mature, according to functional MRI scans utilized by the research.

The study’s authors point out that this is a natural part of growing up, as children gain independence and start to forge their own way in the world.

“Just as an infant knows to tune into her mother’s voice, an adolescent knows to tune into novel voices,” Daniel Abrams, the lead author and an associate professor at Stanford, said in a statement. “As a teen, you don’t know you’re doing this. You’re just being you: You’ve got your friends and new companions, and you want to spend time with them.”

The research was recently published in the Journal of Neuroscience.