New York - A normal human baby, according to psychologists, will cry about two hours over the course of a day.
Current and former whine enthusiasts, take heart. It turns out that infant crying is not only as natural and justifiable as breathing: The two acts are physically, neurologically, primarily intertwined. Scientists have discovered that the small cluster of brain cells in charge of fast, active respiration also grant a baby animal the power to cry.
Reporting in the Proceedings of the National Academy of Sciences, Carmen Birchmeier and Luis Hernandez-Miranda, of the Max Delbruck Center for Molecular Medicine in Berlin, and their colleagues showed that infant mice stripped of this key node - a mere 17 000 neurons, located in the evolutionary ancient hindbrain - can breathe slowly and passively, but not vigorously or animatedly.
When they open their mouths to cry, nothing comes out. As a result, their mothers ignore them, and the poorly breathing pups quickly die.
“This was an astonishing finding,” Birchmeier said. “The mother could see the pups and smell the pups, but if they didn’t vocalize, it was as though they didn’t exist.”
The new study is just one in a series of recent reports that reveal the centrality of crying to infant survival, and how a baby’s bawl punches through a cluttered acoustic landscape to demand immediate adult attention.
The sound of an infant’s cry arouses a far quicker and stronger response in action-oriented parts of the adult brain than do similarly loud or emotionally laden noises, like a dog barking or a neighbor weeping.
Harried parents might prefer the scientists focus on a simple translation manual. What is my screaming angel trying to tell me?
Mariano Chóliz, a psychologist at the University of Valencia, and his co-workers have made a first-pass attempt to categorize infant cries. In The Spanish Journal of Psychology, the researchers described laboratory studies in which infants were subjected to various unpleasant procedures known to elicit different emotional states. The resulting cries were videotaped and analysed.
To provoke anger, the investigators pinned down the babies’ hands or feet and prevented them from moving. To arouse fear, the researchers clapped their hands loudly or dropped a book on the floor. A cry of pain followed “the obligatory vaccination,” according to the study.
Chóliz found that angry babies tended to keep their eyes half closed, gazing off to the side as they cried. They steadily amped up the volume of vocalized umbrage. Frightened babies, after an initial hesitation and tensing up of the facial muscles, emitted an explosive cry and kept their eyes open and searching the whole time.
Babies pained by a needle prick cried out immediately, at full force, and squeezed shut their eyes. They maintained that expression and volume for the entire crying bout.
The take-home message for parents: If you happen to drop a heavy object on the floor while the pediatrician is pinning down your baby’s leg for a shot, your child will be in therapy for life.