There's no known advantage to an adult hiccup. An infant one, however, could play a key role in brain development. That's according to University College London researchers who previously conjectured that a baby discovers its body via kicks in the womb. In this study, they used electrodes on the scalp and sensors on the torso to monitor 13 preterm and full-term newborns for hiccups, which they found helped the babies regulate their breathing, per CNN. Essentially, each hiccup—an involuntary contraction of the diaphragm—produced three brain signals, the last of which is similar to a brain wave triggered by a noise. Researchers therefore believe babies may be connecting the "hic" sound to the physical contraction within their bodies, per the study published in Clinical Neurophysiology.
"When we are born, the circuits which process body sensations are not fully developed, so the establishment of such networks is a crucial developmental milestone for newborns," says researcher Lorenzo Fabrizi in a release. "The activity resulting from a hiccup may be helping the baby's brain to learn how to monitor the breathing muscles so that eventually breathing can be voluntary controlled by moving the diaphragm up and down." While hiccups can be detected as early as nine weeks into pregnancy, babies born at least three weeks premature hiccup often, about 15 minutes per day. Thankfully, that's not the case with most adults, who study co-author Kimberley Whitehead suggests may experience hiccups as "a vestigial reflex, left over from infancy when it had an important function." (A 35-year-old man hiccuped for five days.)