Newborn babies have a remarkable amount of power. Though there are few things they can do for themselves, they can manipulate the world around them by summoning help with a simple wail. Caregivers, especially parents, are particularly sensitive to infants’ cries, which we’d expect because caregivers have an interest in looking after their babies’ needs – they want them to survive.
But is comforting a crying baby more than a conscious, rational response? A new study published in PNAS suggests we are actually hardwired to react in this way. It offers evidence that a baby’s cry provokes specific activity in the brain and leads to similar behaviour in mothers around the world. Yet I would argue this is only evidence of a shared cultural response that could be learned rather than biologically programmed into the brain.
The international group of researchers observed the caregiving reactions of nearly 700 mothers of firstborn, five-month-old babies from 11 countries across five continents. When the infants started crying, the mothers generally didn’t increase their levels of affection (for example kissing) or nurturing (for example feeding). But they almost all responded by picking up, holding, and talking to their baby, suggesting that this behaviour is likely to be universal (as we’d probably expect).
To find out whether these culturally shared behaviours were underpinned by universal neurological activity, the researchers also measured the brain patterns of American first-time mothers of three-month-old babies, and Shanghai Chinese mothers of seven-month-olds. Hearing recordings of babies crying activated brain areas associated with the intention to move and grasp, to speak, and to process sounds. It also activated two brain areas associated with maternal caregiving behaviour.
The researchers imply that since brain activation is similar across cultures, the behaviour is “automatic and deeply engrained in caregivers’ nervous systems”, suggesting it is pre-programmed, hardwired, or biologically predetermined. But it’s not clear why these similar behaviours and brain patterns occur. There are plenty of activities practised in a similar way throughout the world, from driving a car to playing football, that we do not think of as being pre-programmed.
For example, there is evidence that as car drivers focus on maintaining a safe distance from the vehicle in front of them, parts of their brain associated with visual feedback, movement selection, and hand-eye co-ordination are activated. Poor performance, meanwhile, is associated with the activity of brain regions involved in error detection.
If we compared American and Chinese drivers, we would probably find similar brain patterns across the two cultures. But this wouldn’t tell us anything about how the ability to drive a car emerges in humans. We certainly wouldn’t assume car driving was a hardwired ability.
For this reason, I don’t think the new data can support or disprove the researchers’ suggestion. What’s more, they found that the brain regions activated in the mothers were not activated in non-mothers. This suggests that maternal responses to infant crying are not something that mothers are born with, but rather something they learn or develop.
For example, it might be that mothers initially respond to their infant’s cries by nurturing them (feeding, burping, changing their nappies). But by the time their child is five-months-old (as in the study), the mothers discover that holding and talking to the baby is a better way to comfort them. When the infant is even older, a different strategy such as distracting them with a toy might become a better strategy. So, it would be interesting to see whether the maternal responses are fixed or flexible across time.
We do have evidence that the hormone oxytocin, which is associated with maternal bonding behaviours in rats, naturally increases from early to late pregnancy. So it may play a role in forming an emotional bond between the human caregiver and child. But it’s not helpful to think of complex behaviours like parenting as the result of biological factors alone.
For example, oxytocin levels in human parents and their infants increase after they interact. But when orphans who have been neglected by their initial caregivers interact with their foster parents, the children’s oxytocin levels increase by a lower amount. Oxytocin levels even increase in rats when mothers lick their pups. This shows how important social and physical factors can be alongside biological ones.
If researchers want to demonstrate that parental behaviour is biologically predetermined, they could start by comparing brain responses in first-time mothers before and after giving birth. Does pregnancy or birth trigger a switch in mothers that result in them displaying similar responses to those of mothers with a five-month-old, or is the change more gradual, consistent with the idea that responses are developed? Also, they could compare birth mothers with those who recently adopted a baby. Does adoption trigger similar behavioural/brain response patterns?
Alternatively, the researchers could approach the problem by trying to identify what physical, biological, and social interactions might cause maternal responses to develop, taking us away from the old nature versus nurture debate to a more nuanced argument. Without this clearer picture of what’s going on, it’s a big leap to say humans are programmed to respond to a baby’s cry, however natural it might seem.