TierneyMJ/Shutterstock
Source: TierneyMJ/Shutterstock

by Abigail Fagan

Tears are just drops of water, composed of salt, proteins, and hormones. Yet each droplet can be profoundly powerful, allowing us to communicate without a single word, starting in infancy. New findings suggest that for infants, tears serve as an important complement to the sound of crying — sending their own salient signal to caretakers.

To better understand the importance of infant crying, consider that humans have a lengthy childhood and are some of the most helpless of newborn mammals, according to Ad Vingerhoets, a leading researcher on tears and a professor of clinical psychology at Tilburg University in the Netherlands. Since babies lack the ability to move, talk, or find food, the sound they make when they cry prompts caretakers to secure those resources, a concept scientists have likened to an “acoustic umbilical cord.” That sound is powerful, able to pierce through darkness or distance. Sitting beside a loudly crying baby for 15 minutes can even impair our hearing, so we’re highly motivated to alleviate an infant’s distress, says Randolph Cornelius, a psychology professor at Vassar College.

Unfortunately, that power can backfire. Research has shown that caregivers can become irritated or even abusive after exposure to a baby’s crying. “The acoustic part of infant crying was long ago found to be the trigger for abusive behavior of caretakers toward infants,” Cornelius says. The ability to produce tears — a quieter, calmer signal of distress — only develops after an infant’s nervous system matures a few months after birth.

To further understand the signaling power of tears, scientists recently investigated the difference between perceptions of infant tears and adult tears. The team found, perhaps unsurprisingly, that infant tears elicit a stronger response than adult tears, according to a report published in Social Neuroscience. Seeing infant tears activated brain regions related to visual processing and pain perception, which could enable a caretaker to understand the child’s distress and attempt to relieve it, says Vingerhoets, a co-author of the paper.

The same scientists also employed a task in which pictures of adults and infants, with and without tears, appeared as though they either were moving toward or away from the participant. Participants responded more quickly to teary adult faces when the pictures approached rather than receded, but when viewing infant tears, there was no difference between the conditions, according to a paper published in Emotion. People may need the extra cue of approach behavior to react maximally to adult tears, but infant tears seem to register without the extra push. The team also found that women who reported high “maternal love withdrawal” — whose parents reportedly withheld affection in response to their actions — demonstrated less amygdala activity than low-withdrawal women when they viewed adult tears, but demonstrated no difference when they saw infant tears.

The findings provide evidence that responsiveness to infant tears is deeply embedded — showing up even in people who reported a tough relationship with their own parents and were less responsive than usual to adult tears. “We can speculate that our reactions to infant tears are so important, in an evolutionary sense, that they should not be too easily affected by all kinds of non-optimal psychological processes,” Vingerhoets says.

The studies have a few limitations, because the results are correlational, and participants were undergraduate women without children. Further research will need to assess to what extent actual parents display the same response. Yet the current findings may have implications for how tears work in concert with the sounds babies make when they cry. While acoustic crying provides a pointed and potentially aggravating alert, tears may soften parents' aversive responses to it. While the idea is still speculative, Vingerhoets believes this is one possible explanation for our unique two-tiered cries.

“It’s really interesting that there’s some evidence in these two papers that the appearance of tears buffers this aggressive response and may promote a more empathic response to the infant,” says Cornelius, who was not involved with these two studies, but has collaborated with Vingerhoets in the past.

Newborn babies have a meager set of behaviors with which to navigate the first years of life. But as they gradually expand their repertoire, the droplets that help signal their distress appear to be an important addition. “We’ve all evolved as receivers of these signals of vulnerability,” Cornelius says, “to respond with heightened empathy and heightened motivation to provide comfort.”

Abigail Fagan is a former Psychology Today editorial intern.

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