Babies develop language skills within hours of being born.
Scientists at Bangor University in Wales have used optical imaging to measure changes in the bodies of newborn babies in response to language recordings.
Minutes after birth, the tots were played a recording of vowels spoken naturally and vowels played backwards as the experts measured the level of oxygenated blood in the brain.
After five hours of exposure, the babies' brains started to distinguish between the two as their learning continued during hours of sleep.
Dr. Gary Oppenheim, a lecturer in psychology at the university, said: "The work that a newborn's ears and auditory system are doing isn't as obvious to the naked eye, but this spectacular result shows we have a remarkable sensitivity to language information from the very moment we are born and we are immediately set to work developing and refining it in response to our experiences in the world, even when we appear to be just sleeping."