Babies aren't born with the ability to speak, and most of them don't utter much more than a coo, cry or squeal until at least 8 or 9 months of age. However, research indicates that their little brains are soaking in the speech characteristics of those around them from about the age of 6 months [source: Kiester].
Further study has found that infants as young as 5 months old can discriminate between accents, even relatively similar ones like French Canadian and Parisian [source: Cristia, et al.]. Yet another bit of research determined that infants actually cry with an accent of sorts. Obviously, they're not pronouncing words, but their cries mimicked the intonation they heard, with French babies raising the pitch of the cry toward the end of a "sentence," so to speak, and German wee ones doing the opposite. These findings are in line with the accents respectively of French and German adults [source: Kaplan].
University of Washington speech professor Patricia Kuhl has been exploring how humans develop language for more than 25 years — why for instance, American English speakers can easily distinguish between "lake" and "rake" while Japanese speakers can't. Or why an American keeps mixing up chee (wife) and shee (west) when learning Mandarin, which a native speaker wouldn't do.
By working with babies from the U.S., Japan, Sweden and other countries, Kuhl discovered that 6-month-old Japanese babies could distinguish between an "l" and a "r" as easily as American babies. But by the time they were 1 year old, they had lost the ability to do so; instead the babies honed in on the familiar pronunciations and tuned out the "strange" ones. The study involved allowing babies to turn their heads to sounds coming from a loudspeaker [source: Kiester].
"The baby early begins to draw a kind of map of the sounds he hears," Kuhl told Smithsonian magazine. "That map continues to develop and strengthen as the sounds are repeated. The sounds not heard, the synapses not used, are bypassed and pruned from the brain's network. Eventually the sounds and accent of the language become automatic. You don't think about it."
This is great for learning your primary language, but not so great for learning subsequent ones.