Age-old fears perk up baby’s ears

A snake’s hiss is creepy enough to give any kid a fright. And a fire’s crackling may signal danger lurks nearby. Children learn to heed such threatening sounds or else risk peril. Fortunately, a new study finds, kids start paying attention to these types of sounds very early — by the time they’re 9 months old.

This response to scary sounds has evolved in children over tens of thousands of years, the authors propose. In their new study, 9-month-old babies responded strongly to the sounds of ancient dangers.  Such sounds included adults arguing, thunderclaps, a snake’s hiss and a fire’s snap, crackle and pops.

The infants didn’t pay as much attention to pleasant sounds such as classical music or laughing babies. They also didn’t pay as much attention to threatening sounds that are fairly modern. These included breaking glass and wailing sirens.

“There is something special” about the ancient sounds that infants respond to, Nicole Erlich told Science News. A psychologist at the University of Queensland, Australia, Erlich led the new study. She and her coworkers now propose that infants’ brains have evolved to fixate on age-old threats. Their findings appeared Aug. 27 in Developmental Science, a research journal.

Babies are born with their hearing intact. In contrast, other senses such as sight aren’t fully developed and functional until after birth. Erlich proposes that babies develop their attention to perilous sounds while they are still in the womb.

She and her coworkers tested 61 infants. The scientists played recordings of ancient danger sounds, modern danger sounds and pleasant sounds. When the 9-month-old babies heard the ancient danger sounds, their heart rates slowed more. Their eyes opened especially wide during blinks. And they turned to look at their parents more often. These physical cues indicated the babies were paying more attention to the ancient danger sounds, Erlich’s team says.

Psychologist David Rakison of Carnegie Mellon University in Pittsburgh has also conducted studies on infants and fear. He says that studies now suggest babies have evolved to quickly identify what to fear in their world.

But the science isn’t settled yet, he warns. Babies may learn to fear a snake’s hiss and other sounds because they pick up on their parents’ negative reactions, not because of an unlearned fear. That idea needs to be tested, says Rakison.

Power Words

evolution A process by which species undergo changes over time that leave a new type of organism better suited for its environment than the earlier type. The newer type is not necessarily more advanced, just better adapted to the conditions in which it developed.

infant A young child or baby.

psychology The study of the human mind, especially in relation to actions and behavior.