Georgia, United States: Are there biological factors that could help explain why some fathers are more nurturing than others? That’s the question being explored by Emory University anthropologist James Rilling in a series of innovative studies that are documenting how differences in hormone levels, sexual anatomy, and brain activity seem to relate to involvement with children.
For many, many years, we assumed that men’s bodies did not change when they became fathers, which probably seemed logical, since males cannot bear or nurse children. As a result, researchers knew almost nothing about which biological factors might drive fathers to spend time caring for their children.
Since 2013, Rilling and his colleagues have taken this line of research to a new level with surveys, genetic analyses, and brain imaging. They’re discovering what the body and brain of an involved dad looks like—and how it might be different from that of a less-involved father. Their key findings are controversial, to say the least—the interplay between biology and behavior always is—but their work is yielding new insights about what happens in a man’s body as he becomes a father.
Testosterone is the biological force that exerts the most influence over men's care-giving behaviour. In a 2014 study, Rilling and colleagues recruited 88 fathers of young children and 50 unmarried men who were not fathers. They found that the fathers had significantly higher levels of the hormone oxytocin in their blood when compared with the non-fathers.
The researchers found that when fathers looked at the child pictures, they showed greater activation than non-fathers in brain areas known to be involved in the processing of facial expressions and thinking about the mental states of other people. In response to the sexual images, the non-fathers showed greater activation in brain regions associated with reward and motivation than the fathers did. Taken together, these results suggest that fathers are putting more energy into thinking about other people and their needs—and much less energy into chasing what they want.