"Parenting can sometimes make you want to scream, but a new study finds that arguing in front of your baby might sensitize the infant's brain to stress. Researchers at the University of Oregon found that babies react to angry, argumentative tones of voice, even while they are asleep.
Babies' brains have high plasticity, which allows them to quickly learn how to respond to the environments and people around them. Because infants are so responsive, however, severe stresses like abuse and mistreatment can significantly hamper babies' brain development.
Graduate student Alice Graham, along with advisors Phil Fisher and Jennifer Pfeifer, decided to investigate how more moderate stressors affect babies' brain development.
With the help of fMRI brain imaging, they decided to explore the association between babies' brain functions and a common source of stress in young children's lives- the sounds of parental arguments.
Few studies have used neuroimaging to examine infant responses to angry voices in particular brain areas. A 2005 study found that infants' brains devote more attention to angry voices than happy or neutral tones, and a 2010 study suggested that babies are attuned to a voice's emotional state by seven months. Previous research suggested that parental conflict can decrease infants' sleep quality and negatively impact children's emotional well-being.
At their regular bedtimes, twenty infants ranging from six to 12 months old were brought into an fMRI lab. The researchers presented the babies with nonsense sentences spoken by a male adult voice in a range of emotional tones- very angry, somewhat upset, neutral, and happy.
The results showed that, "even during sleep, infants showed distinct patterns of brain activity depending on the emotional tone of voice we presented," said Graham in a press release.
The babies' parents had completed questionnaires about the level of conflict in their homes, and the brain imaging results indicated that infants from high conflict homes showed stronger reactivity to the very angry tone of voice in brain areas including the hypothalamus, cingulate cortex, caudate, and thalamus, which are associated with stress and emotional regulation.
Early life experiences can strongly influence a person's response to events later in life. Animal research has proved that brain areas like the hypothalamus and cingulate cortex influence the impact of early stresses on development, and this study indicates that similar mechanisms are at play in human brains.
The researchers take their results as proof that babies are sensitive to the sounds of parental arguments, though follow-up studies would be necessary to judge the long-term impact of high-conflict homes on babies' brain development.
Parents of infants take note- your baby may not understand what you're saying, but your tone of voice during arguments is all too clear.
The study will be published in the next edition of the journal Psychological Science."