New research suggests babies can literally smell their mother's fear.

Babies could learn what to be afraid of within only the first few days of life by smelling when their mother gets scared, University of Michigan Health System reported.

The researchers observed mother rats who had learned to fear the smell of peppermint and found they "taught" this phobia to their offspring. The findings were published in the most recent edition of Proceedings of the National Academy of Sciences. The findings help demonstrate how a mother's traumatic experiences can affect her children.

"During the early days of an infant rat's life, they are immune to learning information about environmental dangers. But if their mother is the source of threat information, we have shown they can learn from her and produce lasting memories," said Jacek Debiec, M.D., Ph.D., the U-M psychiatrist and neuroscientist who led the research.

"Before they can even make their own experiences, they basically acquire their mothers' experiences. Most importantly, these maternally-transmitted memories are long-lived, whereas other types of infant learning, if not repeated, rapidly perish," he said.

The rats were taught to fear the smell of peppermint by receiving mild electric shocks when they were exposed to it. The study also contained a control group that was not taught to fear the scent. Using special brain imaging and studies of genetic activity in the brain the researchers found the newborns could learn their mother's fear even when they weren't present; in these cases the scent of their mother was piped to them when she was exposed to peppermint. When the team blocked amygdala activity in the baby rats they did not learn to fear the smell of peppermint. This suggests there are ways to intervene and prevent children from learning irrational fears from their mothers early in life.

Debiec has worked with grown children of holocaust survivors who frequently have related nightmares and even flashbacks of their parents' experiences.