My sister recently presented me with a little puzzle to solve: before having her son, she doesn’t think she would have teared up at the ending of Toy Story 3 or the opening of Up; now, despite the repeated viewings my nephew has insisted on, they are guaranteed to wash out her eyes. A few months back I couldn’t tell her whether the cells that migrated from my nephew into her brain during pregnancy caused her sudden enjoyment of potty humor, so this is my chance to redeem myself.
The first step to tearing up at emotional movie scenes is, of course, recognizing the emotion at play. During pregnancy, women become more sensitive to emotional facial expressions: they are better able to identify when a face is sad, scared, angry, or disgusted (through with no improvements in recognizing happy or surprised faces). The authors of that study fingered higher levels of progesterone and estrogen as possible culprits for the change, which might suggest the changes are limited to pregnancy when those hormones are at all-time highs. However, those hormones may leave a lasting legacy of changes in the brain; after all, the evolutionary rationale for higher sensitivity is being better able to recognize the forthcoming baby’s emotions, and good emotion recognition may help prevent mothers from becoming abusive.
Recognizing emotional context is the first step to watery eyes, but the tears aren’t likely to fall unless you truly feel the impact of that emotion, or empathize. Enter oxytocin, the “love hormone” (or “cuddle chemical”, if you prefer alliteration), to ramp up a mother’s empathy. A shot of oxytocin up the nose will make men more empathic toward kittens and crying, and we know that oxytocin flows freely during childbirth to help women bond with their babies. If bathing in oxytocin permanently changes some of the neurons in the brain, then higher empathy – and inclination to tear up at a sad scene – will stay with the new mother far longer than any baby weight.
So pregnancy and childbirth hormones left my sister with a double-whammy: first making her better at recognizing other people’s emotions, and second making her more likely to feel those emotions on their behalf. On the bright side, even though my nephew is now in preschool, she can at least blame the need to reach for a tissue on him.