We’ve written previously that fatherhood is associated with decreased levels of testosterone in dads (except for when a testosterone boost might come in handy). For the most part, the general belief has been that the dads’ lower testosterone limits their impulses to mate (presumably not with their baby-momma), thus keeping them invested in their children.
Some recent research from Emory University, however, suggests another, or additional, possibility.1 Specifically, the researchers compared the testosterone and oxytocin hormone levels of a group of fathers of 1-2 year old children with hormone levels of men without children. In addition to collecting blood samples to measure the hormones, the researchers also scanned the brains (via MRI scans) of all the men while they were looking at 3 types of pictures: 1) children’s faces (of the same sex and age as their own kids, and depicting a range of emotional expressions), 2) unknown adult faces displaying similar emotions, and 3) scantily clad women. The research team was interested in whether fathers vs. non-fathers responded neurologically (i.e., as assessed via increased brain activation) to the different types of images and, if so, what role hormones play in those neural responses.
Consistent with past work, fathers had lower levels of testosterone than did childfree fathers. Interestingly, dads had higher levels of oxytocin than did their childfree counterparts. This is one of the first studies to document a link between oxytocin levels and fatherhood status; the connection makes intuitive sense given the fact that oxytocin is generally implicated in the bonding process. What about those brain scans?
Here’s the especially cool part (at least to this researcher). Fathers, relative to non-fathers, showed more activation in an area of the brain generally believed to be (partially) responsible for emotion processing but only when looking at child faces. And the lower men’s testosterone, the more the ‘emotion processing’ part of the brain became activated, but, again, only when looking at pictures of children (i.e., not when they were looking at adult faces). In other words, fathers appear to be more sensitive to emotional displays by children, and that sensitivity is associated with decreased levels of testosterone (in fact, other work has shown that administering testosterone to participants decreases their ability to empathize with others).2
Oh, and what about those scantily clad women? You probably guessed it….nonfathers “neurologically appreciated” (not a technical phrase) those scantily clad women more so than did the fathers. And, no, it wasn’t just because the dads were too tired to care. In fact, it wasn’t quite clear what might be responsible for dads’ lack of neural responses when looking at scantily clad women — neither oxytocin nor testosterone was associated with the brain activation observed when men were looking at the sexy photos. One possibility is that hormones aren’t involved; rather, perhaps fathers are more invested in their relationships, which makes them more committed. In turn, their increased commitment might cause them to downplay alternatives to their partners more so than those without children. This is conjecture, of course, but certainly in line with what we know about commitment.
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1Mascaro, J., Hackett, P., & Rilling, J. (2014). Differential neural responses to child and sexual stimuli in human fathers and non-fathers and their hormonal correlates. Psychoneuroendocrinology, 46, 153-163. doi:10.1016/j.psyneuen.2014.04.014
2Hermans, E., Putman, P., & van Honk, J. (2006). Testosterone administration reduces empathetic behavior: A facial mimicry study. Psychoneuroendocrinology, 31(7), 859-866. doi:10.1016/j.psyneuen.2006.04.002
Dr. Tim Loving – Science of Relationships articles | Website/CV
Dr. Loving’s research addresses the mental and physical health impact of relationship transitions (e.g., falling in love, breaking up) and the role friends and family serve as we adapt to these transitions. He’s a former Associate Editor of Personal Relationships and his research has been funded by the National Institute of Child Health and Human Development.