The soothing effect is likely due to the release of the hormone oxytocin in the brain, the researchers say. This “love hormone” is known to quell stress, and is likely involved in social bonding, including that between a mother and a child.

Previous work has revealed this hormone was released during physical contact from mom.

“But it’s clear from these results that a mother’s voice can have the same effect as a hug, even if they’re not standing there,” said study researcher Leslie Seltzer, a biological anthropologist at the University of Wisconsin-Madison.