Can babies sense stress in the people who care for them?
Yes, they can. And babies don't just detect our tension. They are affected by it. Stress is contagious. It's one more reason to look after your own well-being -- and to calm down before interacting with your child. Here's what every caregiver needs to know.
You've probably experienced it yourself: Becoming unsettled because someone else is stressed-out.
Is this a superficial reaction? A fleeting mind-trick that mother nature has played on us?
Hardly. In a series of experiments on adults, Veronika Engert and her colleagues discovered they could induce a "full-blown physiological stress response" by merely asking people to watch someone else get stressed.
More than 200 volunteers participated. They took turns sitting in an observation area, watching through a one-way mirror as their domestic partners experienced a moderately stressful social situation -- being tested on their mental arithmetic skills for a panel of judges.
For 40% of the study participants, just seeing their partner under this pressure was enough to raise their own levels of the stress hormone, cortisol. And about 10% of the volunteers responded even when the person being tested was a complete stranger (Engert et al 2014).
"The fact that we could actually measure this empathic stress in the form of a significant hormone release was astonishing," says Engert, "particularly given how tricky it can be to trigger stress-hormone changes in a laboratory setting. If people react like this in a contrived, relatively low-stakes situation, what might they be like in the real world?"
Nobody yet has performed the same hormonal test on babies, but Sara Waters and her colleagues have come close. Instead of measuring cortisol levels, they monitored another physiological marker: the changes in heart rate that accompany the stress response.
The researchers fitted 69 babies (aged 12-14 months) and their mothers with cardiovascular sensors. Then the families were temporarily separated, and the mothers randomly divided into three groups:
After about ten minutes, when the tasks were completed, the mothers were reunited with their babies, and the researchers examined changes in heart function.
Not surprisingly, the mothers who showed signs of the most stress were those in the high-stress condition -- the women who'd delivered speeches to the disapproving judges.
But the interesting
thing is that their stress responses were mirrored by their babies.
Infants of mothers in the high-stress condition experienced--within minutes of being reunited -- matching changes in heart rate. And this stress contagion effect grew stronger over time.
There was also a measurable behavioral effect. Compared with the babies whose mothers had been assigned to the "no-stress" condition, the babies whose mothers had performed public speaking became more reluctant to interact with strangers (Waters et al 2014).
It's likely that the infants were responding to information on multiple channels.
For example, we know that babies are sensitive to the emotional tone of
There is also evidence that babies mirror our brain states when we gaze into their eyes.
And it appears that touch is an important channel too.
Waters and her colleagues tested this possibility in a follow-up study that was much like the first. In this second study, 105 mother-infant pairs experienced brief separations, during which some of the mothers were stressed.
But this time, the researchers added a couple of twists.
1. On being reunited with their mothers, some babies were specifically assigned to be held (placed on their mothers’ laps), while other infants were assigned to a "no touch" condition.
Babies in the "no touch" condition were seated in high chairs alongside their mothers, and allowed to interact by sight and sound. But their mothers were under strict orders not to touch the babies.
2. The experiment didn't end with the mother-infant reunions. Instead, after about 5 minutes of private "together-time," an adult came into the room.
This adult engaged in "innocuous small talk" with the mother, and then, after several minutes, attempted to play with the baby.
But the identity of the adult varied. If you were a mother who had experienced the "no stress" condition, the adult was a friendly lab assistant.
If you were a mother who had experienced the stressful public speaking condition, the adult was one of your judges -- one of the people who had thrown you all those disapproving looks.
What happened next?
You might think the "no touch" policy would be frustrating for the babies, and that seems to have been the case. For example, during the first few minutes after being reunited, babies in the "no touch" condition were more likely to share their mothers’ physiological distress.
But for families in the stressed condition, everything changed after that adult judge came into the room. The mothers’ physiological stress levels increased, and the babies seemed to notice -- if they were sitting on their mothers' laps.
The babies being held by their mothers became ever-more likely to mirror their mothers’ physiological stress responses.
The babies in the no-touch condition did not (Waters et al 2017).
It's as if physical touch were a high fidelity cable – a conduit allowing for the efficient transfer of contagious stress. Without this tactile connection, the babies were less likely to track their mothers’ physiological reactions.
So it’s clear that babies, like adults, experience “second-hand” stress, and babies may be particularly likely to “catch” our distress when we hold them.
This shouldn’t really surprise us. Not if we think about the evolutionary importance of stress contagion. A wide variety of mammals, birds – even fish – learn about fear through social observation (Manassa and McCormic 2012). These animals don’t wait to get bitten before deciding that a predator is scary. They notice the others react with alarm, and take a hint.
And experiments indicate that many creatures experience feelings of empathy for others. For example, rats act agitated or distressed when they see other animals in pain (Langford et al 2006).
We should be ready to attribute even greater abilities to our own children. The brain of a human newborn is massive compared with that of a rat. At birth, babies are already attuned to social information, and within a few weeks they may become savvy enough to notice—and be disturbed by–the sight of apathetic, unresponsive faces.
Of course, this doesn’t mean that babies can read your every thought. Nor does it mean that we’ll cause lasting harm if we sometimes pick up our babies while we are feeling upset.
But babies are far from clueless. They are sensitive to our emotional states, and there is evidence that long-term exposure to second-hand stress -- like the angry squabbling of adult domestic partners -- can alter the development of a baby's stress response system (Towe-Goodman et al 2012; Graham et al 2013).
So reducing our own stress levels isn’t just good for our health. It’s good for our babies, too. Before we interact with our babies, we should take a moment to calm ourselves down.
For tips on handling stress, see these articles
Engert V, Plessow F, Miller R, Kirschbaum C, and Singer T. 2014. Cortisol increase in empathic stress is modulated by social closeness and observation modality. Psychoneuroendocrinology 45: 192-201.
Graham AM, Fisher PA, and Pfeifer JH. 2012. What sleeping babies hear: a functional MRI study of interparental conflict and infants' emotion processing. Psychological Science 24(5):782-789.
Langford DJ, Crager SE, Shehzad Z, Smith SB, Sotocinal SG, Levenstadt JS, Chanda ML, Levitin DJ, and Mogil JS. 2006. Social Modulation of Pain as Evidence for Empathy in Mice. Science. 312(5782):1967-70.
Manassa RP, McCormick MI. 2012. Social learning and acquired recognition of a predator by a marine fish. Anim Cogn. 15(4):559-65.
Towe-Goodman NR, Stifter CA, Mills-Koonce WR, Granger DA and Family Life Project Key Investigators. 2012. Interparental aggression and infant patterns of adrenocortical and behavioral stress responses. Dev Psychobiol. 54(7):685-99.
Waters SF, West TV, Mendes WB. 2014. Stress contagion: physiological covariation between mothers and infants. Psychol Sci. 25(4):934-42.
Waters SF, West TV, Karnilowicz HR, Mendes WB. 2017. Affect contagion between mothers and infants: Examining valence and touch. J Exp Psychol Gen. 146(7):1043-1051.
Image of pensive infant in mother's lap by Don LaVange / flickr
Image of baby looking over mother's shoulder by Amal Ishantha / flickr
A few paragraphs in this article, "Can babies sense stress?" appeared previously in a post for BabyCenter, entitled "You're baby knows, and feels, when you're stressed" (2014).