The Startle Reflex
Written By Sarah Kahle
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What's up with that?
The Moro, or startle, reflex is one of the ways infants come equipped for survival. When a newborn senses a loss of support (Mom dips her while they are dancing) or is startled by a loud noise (Dad drops a saucepan), she'll do the Moro: Her back arches, her arms and legs flail out, her thumb and pointer finger curl into a C shape. Then, as if grabbing onto something, her arms and legs jerk together, with bent elbows, knees, and toes.
Why reach for something that isn't there? Perhaps because people used to be furrier, which gave infants something to grasp. "Early human infants had an advantage if, when they felt like they were falling, they reached out and grabbed on," says Douglas Vanderbilt, a developmental-behavioral pediatrician at Childrens Hospital Los Angeles.
Doctors test the reflex to be sure the nervous system is working properly by allowing an infant's head to drop slightly, simulating a sense of falling and triggering the response.
The Moro reflex first appears in utero, and fades at 3 to 4 months as the brain matures. Good thing, too. Considering how often babies lose their balance learning to sit, crawl, and stand, the reflex would make them look like they were acting out a Jackie Chan movie.
Fortunately, babies develop other ways, such as making eye contact and vocalizing, to attach to Mom and Dad, who have their own reflexive urge: to hold fast to their child.
Did you know? The Moro reflex was named for Slovenian pediatrician Ernst Moro (d. 1951); Moro is also known for discovering that breast milk contains a digestive enzyme not present in cow's milk, meaning they are not interchangeable.
