Many teenagers these days may seem distant and isolated from their parents. A new study involving teens and their moms finds that teens just can’t help but tune out their mom’s voice. In fact, they are more likely to listen to a stranger than to their own mother. “Adolescents have this whole other class of sounds and voices that they need to tune into,” says Daniel Abrams, a neuroscientist at Stanford University.

Researchers studied the brains of younger children and teens ranging from seven to 16 years old. They found that when listening to their moms or unfamiliar woman, the teens’ thoughts—their brain waves— appeared to be gibberish. The researchers could make no sense of it at all. (Maybe when their moms talked, all the teens heard was “blah blah blah blah blah blah blah.”)

The opposite applies to younger children and “tweens” aged eleven and twelve. They listen more closely and respond more quickly to their mothers and less to total strangers. The shift seems to happen between 13 and 14 years old. The reason for this is that, as kids grow up, their brains expand and pay attention more to the outside world and to social connections with peers. The more we grow and grow, the less we rely on our parents and their social connections. We tend to relate more and listen more carefully to people our own age or to people who aren’t family members.