The Noise of modern life may affect "speech and language development" in the very young, according to a study that found the auditory parts of the brains of young mice are slower to organize properly in the presence of continuous sounds. Researchers at the University of California, San Francisco, reared a group of rats in an environment of continuous background noise and found that their brain circuits that receive and interpret sound did not develop at the same rate as animals that were raised in a quieter environment.

Edward F. Chang and Michael Merzenich, co-authors of the study appearing in the journal Science, said that the continuous noise delayed the organization of auditory neurons during a critical two- to three-week period after the rat pups were born. Although the rat is not a perfect model for what happens in humans, the authors note, the study does suggest that high levels of noise might affect some language learning in infants.

"These findings suggest that environmental noise, which is commonly present in contemporary child-rearing environments, can potentially contribute to auditory and language-related development delays," the authors write in Science. The authors noted that, although the brain development was delayed in rats exposed to the noise, “their brains did eventually mature normally.”