Being exposed to arguments between parents is associated with the way babies' brains process emotional tone of voice, say researchers in the journal Psychological Science. The research, conducted by Alice Graham of the University of Oregon, found that infants respond to angry tone of voice - even when they're asleep.
Babies' brains are highly plastic, allowing them to develop in response to the environments and encounters they experience. But this plasticity comes with a certain degree of vulnerability - other research has shown that severe stress, such as maltreatment or institutionalization, can have a significant, negative impact on child development.
Graham and her colleagues 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," says Graham.
Using fMRI scanning, Graham worked with 20 infants, ranging in age from 6 to 12 months. While they were asleep in the scanner, the babies were presented with nonsense sentences spoken in very angry, mildly angry, happy, and neutral tones of voice by a male adult.
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. "Even during sleep, infants showed distinct patterns of brain activity depending on the emotional tone of voice we presented," says Graham.
Previous research with animals has shown that the brain areas in question play an important role in the impact of early life stress on development - the results of this new study suggest that the same might be true for human infants. "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," said Graham.
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Source: Association for Psychological Science