Infants React to Angry Voices Even When Asleep New research suggests that babies’ brains can process emotional tones of voice, a capability that could potentially lead to problems in dealing with stress and emotions.

Researchers from the University of Oregon found that infants respond to angry tone of voice, even when they’re asleep.

Babies’ brains are very malleable, allowing them to develop in response to the environments and encounters they experience. But this adaptability comes with a certain degree of vulnerability: Research has shown that severe stress, such as maltreatment or institutionalization, can have a significant, negative impact on child development.

Graduate student Alice Graham and psychologists Drs. Phil Fisher and Jennifer Pfeifer  wondered what the impact of more moderate stressors might be.

“We were interested in whether a common source of early stress in children’s lives — conflict between parents — is associated with how infants’ brains function,” said Graham.

Graham and colleagues decided to take advantage of recent developments in fMRI scanning with infants to answer this question.

Twenty infants, ranging in age from six to 12 months, came into the lab at their regular bedtime. While they were asleep in the scanner, the infants were presented with nonsense sentences spoken in very angry, mildly angry, happy, and neutral tones of voice by a male adult.

“Even during sleep, infants showed distinct patterns of brain activity depending on the emotional tone of voice we presented,” Graham said.

The researchers found that infants from high conflict homes showed greater reactivity to very angry tone of voice in brain areas linked to stress and emotion regulation, such as the anterior cingulate cortex, caudate, thalamus, and hypothalamus.

This finding is consistent with lab studies on animals that discovered these brain areas play an important role in the impact of early life stress on development.

As such, the results of this new study suggest that the same might be true for human infants.

Researchers believe the findings show that babies are not oblivious to their parents’ conflicts, and exposure to these conflicts may influence the way babies’ brains process emotion and stress.

The study is to be published in the journal Psychological Science.

Source: Association for Psychological Science

Infant sleeping photo by shutterstock.