"The differences found between men in this study cannot necessarily be attributed to the fact that one group is gay," Morris said in an email. "These findings might be useful when considering other social dynamics (like) situations where fathers may take more of a 'primary' role in parenting than has been considered 'traditional' in the past."

Although Morris praised the study as "well-grounded," he also questioned its strong distinction between the so-called maternal pathway and paternal pathway. The distinction is probably much looser than that, he said.

"I would say there are probably some interesting differences between males and females, but I don't know if we could say that one group is more emotional than the other, or more cognitive than the other," Morris said.

Morris added that to further perfect the study, researchers would need to perform the tests before and after parents have children to show that these changes occurred after the birth of their child.

For now, primary caregiving fathers like Hooper say they are heartened by the researchers' findings.

"It does thrill me as a parent because I think we're doing a pretty nice job raising our little girl," Hooper said. "I love that we're having this conversation."

Researcher Feldman was not particularly surprised by the findings, saying she expected to discover some degree of plasticity in the male brain.

"What was surprising was how neatly and how beautifully these things worked together," she said.