PHILADELPHIA — Even in this era of computer chats and cellphone messages, hearing the voice of someone who loves you, moms especially, still carries a mighty biological boost at stressful times. A text isn’t enough, say researchers, who have found that among the virtues of voice is the ability to comfort.

In a 2011 University of Wisconsin study, 68 girls, ages 7-12, had a public-speaking assignment that resulted in high levels of stress hormone in their bodies. One group of girls was allowed to see, touch, and talk to their mothers. Another group communicated with them via instant messages. A third talked to their moms by phone only, and a fourth group had no contact. When hormone production was remeasured, the girls who had heard their mother’s voice produced more oxytocin, which is associated with positive feelings, and the level of the stress hormone dropped.

“There is something about the power of the human voice that is a lot like touch or other kinds of physical contact in that it can release social hormones and decrease stress,” says the study’s lead author, Leslie J. Seltzer. “Communication online, like instant messaging, doesn’t appear to have the same effect.”

That’s not surprising since humans have had a million or so years to learn the intimacies of vocal communication, while written has been around a mere 5,000 or 6,000 years.

That process of gaining familiarity, and comfort, with the sound of your mother’s voice begins in the womb.