Why do people cry when they’re sad? Laugh when they’re happy?
—Michael Postregna, senior marketing major, Illinois State University
Crying and laughing are part of an ancient vocabulary that is free from deception, and that helps us bond with those close to us. We cry for many reasons, most of which we share with other species (e.g., many animals cry in response to physical pain). However, crying in response to emotional pain has only been reported in humans.
Tears are produced by our autonomic (involuntary) nervous system. This is why even actors must conjure painful memories to produce them, as opposed to just commanding their eyes to cry. Over evolutionary time, emotional crying may have helped us survive by communicating our distress to those close to us. Because tears are involuntary, they are a reliable signal of distress.
When we cry, we trigger a similar autonomic response in those able to empathize with us, moving them to emotional discomfort, or even tears themselves. (Ever cried during a movie?) While crying may serve a cathartic role, it also helps us identify who is with us versus who is merely near us. It is easy to imagine how this information could serve to solidify relationships between individuals, and result in stronger associations with those invested in our success and happiness.
Laughter shares many attributes with crying: It is under involuntary control, it is contagious to those who empathize with us, and it is also an honest broadcast of our emotional state. Laughing is a social behavior that helps us bond with those in our group (e.g., we rarely laugh alone).
Laughter likely evolved from the panting behavior of our ancestors, and both gorillas and chimps pant when tickled or when playing. It is notable that both laughter and emotional crying don’t appear in children until around 3.5 months of age, at a point when communication takes center stage.
The autonomic nervous control of crying and laughter is likely why we are liable to mix crying with laughter and yelling when our emotions are sufficiently intense. Together, these three behaviors likely form an ancient three-word vocabulary that remains useful because, being involuntary, it is free from deception.
Andres Vidal-Gadea, assistant professor of molecular neuroethology, School of Biological Sciences
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