Last week at the supermarket, my daughter pulled me aside to choose a Father's Day card for her daddy.
Helping her read the cards was easy; explaining them to her was not (especially the funny ones). So when we got home, I did what any scientifically minded parent would do: I looked to the scientific literature for answers. I was lucky enough to find a journal article published just this month on the neurobiology of fatherhood. It clarified quite a lot.
So here, without further ado, is what I learned about the neurobiological underpinnings of some common Father's Day card greetings.
"You're one in a million!"
"You're one in twenty!" hits closer to the mark, but the sentiment is right. Males from a mere 5 percent of mammalian species exhibit parental behavior in their natural environments. So if you're a mammal with a father around to do some parenting, consider yourself in the lucky minority. Ring-tailed lemurs and bobcats don't have it so good.
"Dad to the bone"
Dad to the hormone might be more like it. The story begins with mom's pregnancy, when dad's prolactin levels go up, followed by an increase in plasma oxytocin levels across the first six months of fatherhood. Higher levels of these hormones in turn predict greater responsiveness to infant cries and paternal stimulatory touch. Meanwhile, testosterone levels go down. This might be a good thing, since fathers with higher levels of testosterone are less likely to touch their infant children or participate in some aspects of toddler caregiving.
"Just monkeying around with my dad!"
Monkeying around can be lots of fun, but choose your monkey wisely. A callitrichid monkey, like a marmoset and tamarin, would be a particularly good choice. Like humans, callitrichid monkeys are cooperative breeders. Dads do some of the heavy parental lifting, but so do other members of the community.
"The best dad on earth"
You don't need neurobiology to know this one's statistically unlikely to be true. But I'm pretty sure dad will overlook the minor inaccuracy and be happy to hear it just the same. After all, it's just a greeting card.
Tania Lombrozo is a psychology professor at the University of California, Berkeley. She writes about psychology, cognitive science and philosophy, with occasional forays into parenting and veganism. You can keep up with more of what she is thinking on Twitter: @TaniaLombrozo