How much do we let our child’s gender influence our parenting habits and decisions? More than we might realize, according to research. It turns out that fathers have different brain responses when they interact with their toddler daughters than they do when they play with their toddler sons.

A study published in the American Psychological Association’s journal Behavioral Neuroscience found that dads of young girls tend to be more present and responsive to their daughters’ needs than dads of toddler sons. Fathers also sang more often to their girls, talked more openly about their emotions and used more analytical words such as “all,” “below” and “much,” according to the study’s findings.

Fathers of young boys, on the other hand, took part in more rough-and-tumble play. They also used more achievement-related language such as “proud,” “win” and “top” when talking to their toddler sons.

Researchers from Emory University and the University of Arizona suggest the differences in interactions may be because dads accept girls’ feelings more easily than boys’. “If the child cries out or asks for dad, fathers of daughters responded to that more than did fathers of sons,” says Jennifer Mascaro, the study’s lead researcher.

In addition to recordings of daily interactions, researchers also used functional MRIs to measure the participating fathers’ brains.

What they found is nothing short of fascinating: According to the brain scan results, fathers of young girls showed a more robust response to their daughters’ happy facial expressions in the area of the brain that controls visual processing, reward, emotion regulation and face processing than fathers who have sons.

Fathers of young boys, however, had a greater response to their sons’ neutral facial expressions.

According to Mascaro, girls may learn to be more empathetic than boys if they have fathers who are more attentive to their needs and more open with their emotions. She suggested that fathers of sons could take the same approach when interacting with their boys, as previous research has linked depression to restricted emotion in adults.

“The fact that fathers may actually be less attentive to the emotional needs of boys, perhaps despite their best intentions, is important to recognize,” says Mascaro. In the end, “We should be aware of how unconscious notions of gender can play into the way we treat even very young children,” adds Mascaro.

Parenthood changes us all—even in ways we don’t often realize.

A version of this post was published November 12, 2017. It has been updated.