I have two kids. One is 3½ and generally sleeps through the night. The other is 14 months old and either fancies himself as living on a farm or simply likes to jack with his parents by waking up most mornings between 4 and 5 a.m. He may or may not go back to sleep after a trip to the milk bar, typically depending on how late we went to sleep the evening prior (it’s uncanny). Most nights, I admittedly sleep through the first of his wake-ups, and, in fact, often have no conscious recollection of ever hearing him squawk for us from the adjacent room. But, when my wife is out of town or taking in a way-too-early spin class, I find myself jumping out of bed with the urgency of a testosterone-fueled (albeit very tired) man-protector, ready to address whatever it is that has awoken young Mowgli.
A recent study by Dr. Sari van Anders and colleagues, out of the University of Michigan, sheds light on the hormonal influences behind my different reactions.1 They wanted to get at the bottom of some contradictory findings in the fatherhood-hormone literature. Specifically, it is generally accepted that men’s testosterone levels decrease when they become parents. This should be no surprise. After all, the effects testosterone has on the body and behavior make more sense when men confront competitive or challenging situations; you don’t need a surge of muscle strength to change a diaper (although I do realize that some would quibble with that statement). In fact, more nurturant and soothing behaviors are actually harder to engage in when experiencing a surge of testosterone. But, here’s the rub: some infant cues, such as baby cries, actually increase testosterone. Until now, it wasn’t quite clear why this was the case, given that nothing speaks to the need for a ‘nurturant and soothing’ dad more than a crying baby. But, importantly, not all interactions with babies require the same approach. Sometimes babies need comforting. Other times they need you to fend off the sabre tooth tiger that is looking for lunch (at least in prehistoric times). Clearly, testosterone is not so necessary for one of these contexts (singing “Hush Little Baby”), but would be quite handy in the other (back off, tiger). Thus, it is possible that testosterone levels fluctuate with the specific parenting demands men face at a given moment.
To test this idea, they took 55 young men and had them listen to a baby cry, but either (a) did not let them do anything about it (they just had to sit there and listen), (b) gave them an opportunity to effectively soothe the baby, or (c) gave them an opportunity to soothe the baby, but stacked the deck against these guys such that the baby couldn’t be soothed. (That’s just plain wrong.) How did they manipulate the baby’s behavior? They used a very realistic doll that is often used in parenting classes, the RealCare Baby II-Plus. 
The researchers were able to program the baby to do whatever they wanted, and the guys were told to “imagine the baby doll was the real baby of a close friend.” All the guys provided saliva samples before and after the interaction with the baby so the researchers could determine whether the guys’ testosterone levels changed.
Sure enough, the group of men that was able to soothe the baby showed a drop in testosterone, whereas the group of men that was not given any opportunity to soothe the baby showed an increase in testosterone. The guys in the third group – those who tried, but failed at soothing the baby – fell in between and didn’t differ from a control group of men who didn’t have any exposure to a baby. The researchers argue that these men fall in the middle because they engage in soothing behaviors, which should lower testosterone, but they’re unable to stop the crying, which should raise testosterone (i.e., the two experiences cancel each other out).
So here’s my thinking. When my wife is around, I know our son will be soothed, because she’s into that sort of thing (not that I’m not, she’s just more into it), so I can just keep on slumbering and preserve any testosterone that my married, fathering body has left. But, when she’s gone, my son’s cries signal threat to me, so I see a momentary spike in testosterone long enough to save him before his hunger becomes too much to handle. But, because I’m able to soothe him, I can go right back to my low testosterone way of life. Importantly, most of the study participants were not actually fathers. Thus, it appears that men, not just those with kids, are wired to protect and soothe when needed.
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1van Anders, S. M., Tolman, R. M., & Volling, B. L. (2012). Baby cries and nurturance affect testosterone in men. Hormones and Behavior, 61, 31-36.
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 of friends and family during these transitions. He is an Associate Editor of Personal Relationships and has been funded by the National Institute of Child Health and Human Development.
image sources: godspeaking.files.wordpress.com & helago-cz.cz 
