It's the middle of the night and the baby starts to cry; it's feeding time. If you're the daddy, there's a pretty good chance you won't react the same way as the mommy.
It's long been suspected that women’s brains are hard-wired to respond to the cries of a hungry infant. And now, researchers at the National Institutes of Health say there's evidence to back that up.
The researchers asked men and women to let their minds wander, then played a recording of white noise interspersed with the sounds of an crying baby. Brain scans showed that, in the women, patterns of brain activity abruptly switched to an attentive mode when they heard the infant cries, whereas the men’s brains -- well, you know.
The mommy instinct
“Previous studies have shown that, on an emotional level, men and women respond differently to the sound of an infant crying,” said study co-author Marc H. Bornstein, Ph.D., head of the Child and Family Research Section of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), the institute that conducted the study. “Our findings indicate that men and women show marked differences in terms of attention as well.”
The earlier studies showed that women are more likely than men to feel sympathy when they hear an infant cry, and are more likely to want to care for the infant.
Previous studies have shown differences in patterns of brain activity between when an individual’s attention is focused and when the mind wanders. The pattern of unfocused activity is referred to as default mode, Dr. Bornstein explained. When individuals focus on something in particular, their brains disengage from the default mode and activate other brain networks.
For about 15 minutes, participants listened to white noise interspersed with short periods of silence and with the sounds of a hungry infant crying. The patterns of their brain activity were recorded by a technique known as functional magnetic resonance imaging.
Parents vs. nonparents
The researchers analyzed brain images from 18 adults -- parents and nonparents -- and found that when they listened to the typical infant cries, the brain activity of men and women differed. When hearing a hungry infant cry, women’s brains were more likely to disengage from the default mode, indicating that they focused their attention on the crying.
In contrast, the men’s brains tended to remain in default mode during the infant crying sounds. The brain patterns did not vary between parents and nonparents.
Babies cry because they are distressed, hungry, or in need of physical closeness. To determine if adults respond differently to different types of cries, the researchers also played the cries of infants who were later diagnosed with autism. An earlier study found that the cries of infants who develop ASD tend to be higher pitched than those of other infants and that the pauses between cries are shorter. In this other study, both men and women tended to interrupt their mind wandering when they heard these cries.
“Adults have many-layered responses to the things infants do,” said Dr. Bornstein. “Determining whether these responses differ between men and women, by age, and by parental status, helps us understand instincts for caring for the very young.”
In an earlier study, Dr. Bornstein and his colleagues found that patterns of brain activity in men and women also changed when they viewed an image of an infant face and that the patterns were indicative of a predisposition to relate to and care for the infant.
Such studies documenting the brain activity patterns of adults represent first stages of research in neuroscience understanding how adults relate to and care for infants, Dr. Bornstein explained. It is possible that not all adults exhibit the brain patterns seen in these studies.
Dr. Bornstein collaborated with Nicola De Pisapia, Ph.D., Paola Rigo, Simona DeFalco, Ph.D., and Paola Venuti, Ph.D., all of the Observation, Diagnosis and Education Lab at the University of Trento, Italy, and Gianluca Esposito, Ph.D., of RIKEN Brain Science Institute, Japan.
Their findings appear in NeuroReport.