Any wilderness expert will tell you the most dangerous animal to see in the wild is a baby bear. Accidentally stumbling between a mother bear and her cubs is a sure way to get mauled. Mothers will do anything for their children and none of us would be here today if it wasn’t for the selflessness of our ancestors, putting the survival of their offspring sometimes before themselves.
So apparently, the most basic drive for self-preservation can be trumped by babies. While we can’t live forever, we can pass on our genes. Thus, what Richard Dawkins termed “selfish genes” have created animals built for their own survival, and that drive for self-preservation can be redirected to reproduction and then parental care.
The Power of Hormones
I’m sorry to be the one to tell you this, but the areas of your brain responsible for decision-making can be overpowered by hormone-driven signals from deeper brain regions. During development, hormones influence the structure of our bodies, including our brains. During puberty, the same hormones can act again on these existing systems to make you feel awkward during gym class. But perhaps the largest natural shift in hormone concentrations is during pregnancy.
The milieu of hormones pregnant women experience can make long-lasting structural changes to the neurons in our brain. The neurons in deep brain regions responsible for maternal behavior can grow in size when exposed to pregnancy hormones such as estrogens. So, the same time motherhood occurs, the brain is experiencing significant changes. The growing neurons start to communicate with areas of the brain that make the signaling molecule dopamine.
Dopamine rules what neuroscientists call “the reward pathway” and it’s the reason you like anything… ever… in your entire life. Your body releases this magical molecule when you perform activities that will keep you and your genes alive and spreading. Dopamine is released while consuming food or having sex, and because your genes want to be passed on, the drive for parental care relies on this reward pathway too. Large doses of estrogen, such as those occurring during late stages of pregnancy and labor trigger the release of dopamine, stimulating the reward system. This makes new mothers primed and ready to love that 7 pound 5 ounce screaming, floppy pile of responsibility, you named “Aden.”
Hormones lead to new and permanent changes in brain circuitry, which is how areas of the brain interact and respond to one another’s activity. Perhaps surprisingly, animals that haven’t been around babies are not initially fond of infants. Virgin, pup-inexperienced female mice have a natural avoidance to infant stimuli, which is not completely unreasonable. Think about what a baby would seem like if you didn’t know what it was: they cry for seemingly no reason, smell, and demand a lot of time, money and attention. In mice, researchers have explored a natural avoidance and defensive response associated with animals that are new to infant care. There are defined circuits in the brain responsible for this avoidance response. The hormones of pregnancy, silence this circuit, and neural circuits responsible for maternal responses can then be more active.
Changes in Behavior
You might have heard from your friendly neighborhood neuroscientist you don’t have free will. Let me reassure you that yes, you’re a slave to the power of babies. The immediate changes in a mom’s behavior after childbirth suggest major changes are occurring in brain circuitry. This new baby addiction or “sensitization” is caused by changes in the reward system’s dopamine release. Cocaine and other addictive drugs trigger the reward system and release dopamine throughout the brain. Like a drug, the allure of babies is so strong that when given the choice, rats with maternal experience prefer to enter a room associated with infant pups over associated with cocaine. Using this knowledge, let’s take care of two societal problems at once: “Orphanages: The New Methadone Clinic!”
Sensitization causes mothers to act differently. Mother rodents show increases in risk-taking behavior. For example, mother mice on an elevated maze with enclosed and open arms, will spend more time exploring the potentially dangerous open arms than virgin mice. On the up side, new mothers display increases in memory. In a maze, mother rats were better than virgins at remembering where the food was and were faster to retrieve it. The researchers concluded that improved foraging memory increases the chance of survival for a mother’s pups. If this held true in humans, the concept of “baby brain” might be unfounded. However, funding cuts have halted the construction of the human-sized maze stocked with baby supplies.
Even abstaining from motherhood won’t save you from becoming a slave to baby overlords. Mere exposure to infants can activate changes in the brain regions responsible for maternal behavior, and start the process of sensitization in rodents. The process does take more exposure time than in natural mothers, without the surge of hormones to speed things along. This suggests that women become “baby crazy” by exposure to infant stimuli. While we all might inherently be ambivalent or avoid infants, through exposure to babies, they become conditioned and highly rewarding stimuli. Do you want kids? Then it might already be too late.
Not being female won’t save you either. A study looking at brain activity using an fMRI machine found that when fathers are shown images of their children, they display similar brain activity as mothers. Recent research out of Emory made headlines when it found this increase in activity in the reward pathway was inversely correlated with testes size, and blood testosterone concentration. The conclusion: more parental care equals less testosterone and smaller balls, fellas!
The combination of a higher consciousness and a desire to reproduce means, unlike other animals, humans are presented with the question of if we should reproduce. However, the reason they instruct you on airplanes to put the air mask on yourself before you assist young children is because the human drive to protect our genes, I mean, children, sometimes overrides logic. There’s also an illogical drive to have our own children. In a planet with millions of orphan children, you would assume that the baby-loving masses (and cocaine addicts) would decrease the supply of foster kids overnight. However, our biological nature has a way of convincing humans that we don’t just want a child, but we want our child.
In a modern environment where motherhood is a choice, it’s illogical for anyone to be pressured to give birth to an eighteen-year commitment. Because not all people (or laboratory animals) naturally become sensitized to infants, it might be better for everyone if people who don’t want children aren’t pressured to have them. By simply understanding the literally mind-altering process of parenthood, individuals can make decisions that benefit everyone, including our baby overlords.
This article was originally published by Inscripto Magzine, produced by the Science Writers Association of Emory. Written by Emory graduate students for the public at large, this organization helping to support science communication. To find more articles written by members of Emory’s Neuroscience program and other students on a range of science topics, please peruse their new Spring 2015 issue. Direct link to this article at here.