Some of the most troubling images of the opioid crisis involve parents buying or using drugs with their children in tow. Now new research offers a glimpse into the addicted brain, finding that the drugs appear to blunt a person’s natural parenting instincts.

Researchers at the Perelman School of Medicine at the University of Pennsylvania scanned the brains of 47 men and women before and after they underwent treatment for opioid dependence. While in the scanner, the study subjects looked at various images of babies, and the researchers measured the brain’s response. The brain scans were compared with the responses of 25 healthy people.

What the study subjects didn’t know was that the photos had been manipulated to adjust the “baby schema,” the term used to describe the set of facial and other features like round faces and big eyes that make our brains register babies as irresistible, kicking in our instinct to care for them. Sometimes the babies’ features were exaggerated to make them even more adorable; in others, the chubby cheeks and big eyes were reduced, making the faces less appealing. Studies show that a higher baby schema activates the part of the brain called the ventral striatum, a key component of the brain reward pathway.

Compared with the brains of healthy people, the brains of people with opioid dependence didn’t produce strong responses to the cute baby pictures. But once the opioid-dependent people received a drug called naltrexone, which blocks the effects of opioids, their brains produced a more normal response.