The scenario is all too common—children who are abused develop an attachment to their abuser that interferes with their desire to seek help or leave the situation. Experts have struggled to understand this seemingly destructive behavior, but the underlying causes have remained hidden. Now new research from scientists who study attachment in rats offers insight into what may be happening in abused children’s brains.

Rats are especially responsive to smells during infancy, which may help foster the parental bond. Psychologist Regina M. Sullivan of New York University showed in 2000 that young rats are drawn to almost any odor, even when the odor is associated with a stressful stimulus, such as a mild heat shock. In other words, baby rats are attracted to the very thing that hurts them, rather than being repelled as older rats would be.

What is happening in the young rats’ brains to foster attachment instead of aversion or fear? In a new paper in Nature Neuroscience, Sullivan and Gordon Barr, a psychologist at the Chil­dren’s Hospital of Philadelphia, found the answer in the rats’ amygdala, a brain region associated with anxiety and fear. In the amygdala of rats attracted to the aversive odors, there were lower than normal levels of the neurotrans­mitter dopamine. This lack of dopamine activity may have turned off their brain’s fear response, enabling attraction to take place instead. A similar mechanism may occur in abused children, Sullivan says, although how much the amygdala is involved with early human attachment is un­clear. Barr suggests this behavior probably evolved as a survival tactic. “The animal has to be able to survive, which means it has to be attached to its caregiver no matter what the quality of care,” he says.