Even when they're only 3 months old, infants can recognize human sounds like coughing or laughing. And if the sounds are negative in nature, the babies' brains show activity in areas involved in emotion.
"It is probably because the human voice is such an important social cue that the brain shows an early specialization for its processing," said Anna Blasi of King's College London, one of the researchers in a study involving scanning the brains of babies between 3 months and 7 months old. "This may represent the very first step in social interactions and language learning."
While the babies were sleeping in the scanner, the researchers played neutral humans sounds, such as coughing or yawning, and compared the babies' brain reactions with those produced when the babies heard sounds of water or toys.
The part of the brain that in adults reacts to human vocalizations lit up when the researchers played the neutral human sounds, the researchers said in a statement.
"We were very surprised to find that the area of the temporal cortex that responded to the human voice more than to environmental sounds was so similar in its location to the adult area showing the same specialization," study researcher Evelyne Mercure of University College London said.
When the little participants heard sad sounds such as crying, there was an increase in brain activity in regions associated with emotional processing in adults, which could mean babies are already able to empathize and understand different emotional states.
"We are now carrying out more research in this area to help us understand how differences in brain development arise, if we can use these to accurately identify babies who will go on to suffer from disorders such as autism, and if they can be used to help measure the effectiveness of interventions," added study author Declan Murphy, also of King's College London.
The study will be published online today (June 30) and will be in the July 26 print issue of the journal Current Biology.