Even when competing with traffic, a noisy room, digital and background noise, our brain is able to focus on one conversation. However, for those moments when we truly can't hear our conversation partner, our brain handily fills in the blanks without us necessarily realising.
Lead researcher Matthew Leonard and his team worked with subjects who were already being monitored for epilepsy through the help of hundreds of electrodes in the brain. These same electrodes could also be used to observe other types of brain activitiy. The volunteers were played partially inaudible or obscured words to volunteers , a word that could either be 'faster' or 'factor' with a noise subbed in for the middle sound and it was noted that test subjects brains responded as though they had, in fact, heard the 's' or 'c' sound that had been omitted.
The reason? The part of the brain that predicts what word someone is going to hear does this two-tenths of a second before the part that starts processing the sound a person has actually heard.
"The brain puts in the acoustics that are missing," explained David Poeppel of New York University.