Why do some expectant fathers experience pregnancy symptoms such as vomiting and nausea?
—D. Barrera, McAllen, Tex.
Katherine E. Wynne-Edwards is a professor of biology at Queen’s University in Kingston, Ontario, who studies hormonal changes in expectant fathers. She answers:
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MANY FACTORS—from social to hormonal—could play a role when an expectant father experiences typical pregnancy side effects such as nausea, weight gain, mood swings and bloating. The condition is called couvade, from the French verb couver, which means “to hatch” or “to brood.” Across a wide range of studies—and an equally wide range of definitions of what constitutes couvade—estimates of the frequency of couvade range from less than 20 percent to more than 80 percent of expectant fathers.
Only recently has this phenomenon received attention from scientists, spawning a variety of hypotheses. Because a couple may experience lifestyle changes together, the cravings and increased appetite of a pregnant wife may pave the way for her husband’s weight gain, heartburn and indigestion. Conversation at home can range from frustrated incapacitation to boundless anticipatory joy, fostering jealousy of the ability to carry a child, guilt over having caused this transformation in his partner and selfish attention seeking. Changes in sexual activity, shifts in social priorities, time off work, or the arrival of a mother-in-law for a potentially stressful extended visit may also contribute.
Some studies suggest that men who have deep empathy toward their pregnant partner and who are prone to couvade symptoms end up with strong attachments to their child. If this is the case, the symptoms might either stimulate or result from underlying biological processes that are involved in social attachment.
Recent studies also have shown that some of the same hormones that fluctuate for pregnant women are also affected in future fathers. Men with higher levels of prolactin, which causes lactation in women, report more couvade symptoms. Paternal prolactin causes a decrease in testosterone and sperm production and peaks just before delivery. Levels of cortisol (a steroid hormone secreted in response to stress) and the sex steroids estradiol and progesterone also change in the father, though not as much as do those in the mother.
Unfortunately, we do not know yet whether current connections between hormonal changes and behaviors are cause-and-effect patterns or just correlations. No doubt testosterone concentration is lower in men in relationships, for instance, but it is unclear whether men have a decrease in testosterone after the relationship begins or whether men with lower testosterone are more likely to enter into stable relationships. It is tempting to look to hormones as the biological root of couvade, but other social and emotional factors could be equally influential. Either way, questions in this area have quietly expanded the horizons for research on male hormone levels—testosterone alone is clearly no longer the sum of the man.
Why can’t you tickle yourself?
—T. Bogaerts, Lebanon, Tenn.
Sarah-Jayne Blakemore, a research fellow at the Institute of Cognitive Neuroscience at University College London, responds:
THE ANSWER LIES at the back of the brain in an area called the cerebellum, which is involved in monitoring movements. Our studies at University College London have shown that the cerebellum can predict sensations when your own movement causes them but not when someone else’s does. As a result, when you try to tickle yourself, the cerebellum predicts the sensation, and this prediction is used to cancel the response of other brain areas to the tickle.
Two brain regions are involved in processing how tickling feels. The somatosensory cortex processes touch, and the anterior cingulate cortex processes information related to pleasurable sensations. We found that both these regions are less active during self-tickling than they are when someone else is doing the poking. This fact helps to explain why tickling ourselves does not feel tickly and pleasant.
Studies using robots showed that having a small delay between your own movement in starting the tickling motion of the machine and the resulting prod can make the sensation feel tickly. Indeed, the longer the delay, the more tickly it feels. So it might be possible to tickle yourself, if you are willing to buy a couple of robots.
