Welcome to the world. I'll be your mommy -- er, monkey.

Corey Binns of LiveScience reports on a presentation at the AAAS by psychologist Athena Vouloumanos:

Straight out of the womb, infants are just as aroused by a rhesus monkey call as by human speech.
...
"It was very shocking," Vouloumanos told LiveScience. "I thought for sure that they would prefer the human speech. I kept testing more babies because I couldn't believe it."

This was a "suck" test, where they measure how hard the babies suck on special pacifiers in response to different noises. Three-month-old babies liked human speech more than they liked monkey noise.

It does make you wonder if there is a sort of "imprinting" stage during which babies are conditioned to like human voices. The article mentions that newborns are more aroused by folk music than white noise -- I can confirm and extend this, since our babies seemed to be highly aroused by Big Bad Voodoo Daddy.

But voices may be harder to distinguish from monkey noise than rhythmic music is from white noise. It may be another of those deep social brain problems.