Fortunately, they learn the difference after around 3 months

Feb 20, 2006 11:59 GMT  ·  By

Infants put great weight on using their hearing. Various studies have shown that infants appreciate music more than white noise or silence. And four-month babies like listening to people talking more than they like hearing white noise.

But how can one determine whether an infant likes something more than something else? There are two basic ways: one is to listen to how the baby's heart beat changes and another, more sophisticated technique, is to give them pacifiers that can measure the frequency and intensity of the baby's sucking.

"There are all kinds of suckers: soft suckers, hard, rapid and slow. When they suck hard, they get to hear a sound, and when they're aroused they suck hard," said Athena Vouloumanos, the psychologist at McGill University who conducted the current study.

What Vouloumanos found was stunning: new-born infants like listening to rhesus monkey calls as much as listening to human speech. The researchers tested babies that were 10 to 96 hours old by playing them either recorded sounds of human speech or recordings of monkey calls. (They chose to use rhesus monkey calls because they have a similar vocal tract to humans.)

The babies sucked the same for both sounds.

"It was very shocking," Vouloumanos said. "I thought for sure that they would prefer the human speech. I kept testing more babies because I couldn't believe it."

The team has found that, by three months, the babies are aroused by human speech more than by monkey calls. However, this seems to be caused by the fact that the baby learns to recognize human speech during the first months, and not by some inborn capacity.

"If these babies spent the first three months with rhesus monkeys, maybe they'd prefer monkey calls," Vouloumanos said.