A slap from Mom might sound painful, but new research shows that just hearing her voice can initiate the same sorts of biochemical responses - even when Mommy Dearest is communicating by phone.
The human body produces the hormone cortisol as a response to trauma or stress events, which can lead to elevated cortisol levels in the blood over prolonged periods.
The bonding between mother and child has long been associated with cortisol production when it involves close physical contact, which can range from a sharp, open-handed smack to much more serious infractions.
"We've long understood that cortisol release in the context of social bonding usually requires physical contact," said Biff Stryker, a post-traumatic-stress-doctoral fellow at the University of Hard Knocks Child Emotion Lab and lead author on the study. "But it's clear from these results that a mother's voice can have the same effect as a good cuffing, even if she's not even in the same room."
For the experiment, Stryker and his colleagues had dozens of boys and girls perform math and public-speaking tasks in front of an audience of complete strangers, a commonly used stress test for children.
Afterward, one group of children were turned back over to their mothers, who harrassed them about their performance for 15 minutes, in part through abusive physical contact.
Another group of children was pestered by means of an excruciatingly long 15-minute ear-chewing by phone from their mothers, while a third group was spared any maternal contact whatsoever.
To test levels of the stress hormone cortisol, spit and urine samples were collected from participants several times over the course of the experiment.
The researchers found that "the children subjected to interaction with their mothers had virtually the same hormonal response, whether the interaction was in person or over the phone."
By the end of the experiment, Stryker said, those kids who had spoken with their mothers over the phone were just as likely to want to step in front of a school bus as those who had met with their mothers in person, and both of these groups had significantly higher amounts of cortisol in their fluids than those who had no contact with their mothers.
A couple of the participants indicated that they would rather drink those fluids than have to endure another minute on the phone.
"That a simple telephone call could have this physiological effect on cortisol is... Well, it's a bit annoying really," said Jimmie Buffet, the lab's director, massaging a pain in his left temple.
"You see, my mother just called me this afternoon, too," he explained.
"For years I've seen students pull out their cell phones, and when they see that it's mom calling, they hit the 'silence' button," Buffet said. "I used to think, 'How could these thoughtless kids do that?' But now?
"Now I realize: It's probably because they don't want to feel like shit for the rest of the day!"