When we think of someone that "hears voices" often what comes to mind is someone who has suffered a brain injury or perhaps is mentally ill. However, that's not the entire story. Those who hear voices that the rest of us cannot (and who are not diagnosed with any mental illness), seem to have a particular way of processing new sounds in the brain.
New research, published in the journal Brain, shows that voice hearers can pick up sounds more quickly and more accurately than those who don't hear voices obscured by other sounds. Scientists from Durham University and University College London (UCL) conducted the study, and it suggests that the ability to decipher intelligible speech from a jumble of noises is enhanced in people who hear voices versus those who do not.
The study was valuable because it provided a look at the mechanism of the brain and how it decodes auditory stimuli. While it did not involve participants who had a mental health disorder, seeing how sound is broken down in the brain of someone who, while not mentally ill, is not exactly neurotypical either is valuable research. Uncovering that brain process could be part of the way forward in finding treatments for people who are bothered by what they hear in their heads, and who do go on to have a mental illness.
Hearing speech that others don't is formally called an auditory verbal hallucination. In the study at Durham, the volunteers listened to sine-wave speech. Sine-wave speech contains words, however other layers of sound are included that disguise the words, making them hard to pick out from the all the rest of the noise surrounding them. The study participants were asked to listen to different clips of sine-wave speech while undergoing a functional magnetic resonance scan (fMRI.) If a person is told to pay close attention to the clips to see if they can sort out any intelligible words, or if they are trained in what to listen for, very often they can pick up phrases and sentences buried under the sine-wave speech. Sine-wave speech is described as sounding like a bird chirping or "alien" noises, usually heard in science fiction movies. In the study, underneath these sounds were simple phrases like "The boy ran down the path" or "the clown had a funny face."
The group of study participants comprised 12 people who were "voice hearers" and 17 subjects who were not. In the voice-hearing group, 75% accurately heard and reported the words spoken under the sine-waves as opposed to only 17% of those who were non-voice-hearing. None of the participants in either group were told whether or not the sounds they were hearing contained disguised voices, nor were they asked to listen carefully to pick up anything other than the sounds being played. The scans showed that brain activity in those who could hear the voices was increased and activated in regions that are responsible for paying attention and monitoring what is happening in the surrounding environment.
Dr. Ben Alderson-Day, a Research Fellow from Durham University's Hearing the Voice project and the study's lead author, explained, "These findings are a demonstration of what we can learn from people who hear voices that are not distressing or problematic. It suggests that the brains of people who hear voices are particularly tuned to meaning in sounds, and shows how unusual experiences might be influenced by people's individual perceptual and cognitive processes." Study co-author Dr. Cesar Lima from the Speech Communication Lab at UCL added, "This was interesting to us because it suggests that their brains can automatically detect meaning in sounds that people typically struggle to understand unless they are trained." The video below, from the University of Durham, gives more detail so check it out.