Babies who hear their parents arguing are more sensitive to stress In order to develop, babies' brains are malleable - but this also makes them vulnerable to extreme stress Babies from 'high-conflict' homes respond more to angry tones than those from low-conflict homes The response is in the area of the brain linked to stress Babies who hear their parents arguing are more sensitive to stress, new research has found. American researchers found that babies" brains respond to an angry tone of voice even when they are asleep. Babies' brains are highly malleable to allow them to develop in response to their environment and experiences. But this malleability also leaves them vulnerable to developmental problems if they experience extreme stress, such as neglect or abuse. Babies' brains are vulnerable to extreme stress, researchers have warned Researchers at the University of Oregon used MRI scans to study the brains of 20 babies when they were asleep. While they slept in the scanner they were exposed to the sound of sentences being spoken very angrily, mildly angrily, happily and in neutral tones. "Even during sleep, infants showed distinct patterns of brain activity depending on the emotional tone of voice we presented," Alice Graham, a doctoral student involved in the study, said. "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," she added. The researchers found that infants from high-conflict homes showed greater reactivity to very angry tones of voice in brain areas linked to stress and emotion regulation. Previous research with animals has shown that these brain areas 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 researchers found that infants from high-conflict homes showed greater reactivity to very angry tones of voice According to the researchers, the findings show that babies are not oblivious to parental conflicts, and exposure to them may influence the way babies' brains process emotion and stress. This research comes just after another study which showed that babies can also be affected by subjection to stress while in the womb. Researchers at the University of Pennsylvania's School of Veterinary Medicine in the U.S. found that a pregnant woman can transmit the damaging effects of stress to her unborn child through the placenta. The impact is felt by a protein that affects the developing brains of boys and girls differently, they found. Scientists believe this could explain known links between maternal stress and disorders such as autism and schizophrenia, which are more common and serious in male offspring.