Summary: A new study published in Brain finds that people who experience auditory verbal hallucinations are better at detecting concealed speech within ambiguous sounds than those who do not hear voices.
Source: Durham University.
People who hear voices that others cannot may process new sounds differently, using cognitive strengths that help them detect hidden speech in ambiguous auditory signals, according to research led by Durham University and University College London (UCL).
A study published in the journal Brain reports that individuals who regularly hear voices—but do not have a diagnosed mental health condition—recognised disguised, speech-like sounds faster and more readily than people without a history of voice-hearing.
The results indicate that these voice-hearers have an increased tendency to extract meaningful speech patterns from unclear or degraded sounds. The researchers say this offers insight into the perceptual and brain mechanisms that underpin voice-hearing in people who are not clinically unwell, and could inform clinical approaches to support people who find their experiences distressing.
The experiment tested participants using sine-wave speech, a type of degraded audio that resembles birdsong or alien-like noises until listeners are told it contains speech or are trained to decode it. Once understood, sine-wave sentences become clear—for example, “The boy ran down the path” or “The clown had a funny face.”
While undergoing functional MRI scanning, participants passively listened to sets of sine-wave speech that were either potentially intelligible or intentionally unintelligible. Many of the non-clinical voice-hearers recognised the hidden sentences before being informed that the sounds contained speech and, on average, they detected intelligibility earlier than control participants with no history of hearing voices.
Neuroimaging showed that, compared with meaningless sounds, intelligible sine-wave speech produced automatic responses in voice-hearers in brain regions tied to attention and monitoring, such as the dorsal anterior cingulate cortex and the superior frontal gyrus. Across both groups, intelligible degraded speech activated a typical left-lateralised speech-processing network, but voice-hearers showed stronger responses in areas associated with attention and sensorimotor processes.
The study was small but carefully controlled. It included 12 non-clinical voice-hearers and 17 matched controls. Nine of the 12 voice-hearers (75 percent) reported hearing the hidden speech, compared with eight of 17 controls (47 percent). These behavioural differences corresponded with distinct neural signatures when participants heard potentially intelligible stimuli.
Lead author Dr Ben Alderson-Day, Research Fellow with Durham’s Hearing the Voice project, said the findings highlight what can be learned from people who experience voices without distress. “Our results suggest the brains of people who hear voices are particularly tuned to extracting meaning from ambiguous sounds,” he said, “showing how individual perceptual and cognitive processes may shape unusual experiences.”
Co-author Dr César Lima of UCL’s Speech Communication Lab added that participants were not told before scanning that the sounds could contain speech, nor were they instructed to try to interpret them. “Despite that, voice-hearers showed distinct neural responses to disguised speech compared with meaningless sounds,” he said. “This suggests their brains can spontaneously detect meaning where others typically need training or prompting.”
Although voice-hearing is commonly associated with psychiatric diagnoses such as schizophrenia or bipolar disorder, many people in the general population experience voices without clinical need. Previous research estimates that between five and 15 percent of people have had an occasional voice-hearing experience, while roughly one percent experience more complex or frequent voice-hearing without requiring psychiatric care.
Durham’s Hearing the Voice project aims to deepen understanding of how and why people sometimes hear voices when no one is speaking. The interdisciplinary initiative brings together researchers from different fields, clinicians, and people with lived experience of voice-hearing to inform policy and therapeutic practice—particularly in cases where voices are distressing and clinical support is sought.
Professor Charles Fernyhough, Director of Hearing the Voice at Durham University, noted the collaboration with UCL’s Speech Communication lab as an opportunity to examine a commonly troubling but widely misunderstood experience. Professor Sophie Scott of UCL added that the work demonstrates how unusual voice experiences may be rooted in everyday perceptual processes.
The study involved researchers from Durham University, University College London, University of Porto (Portugal), University of Westminster and University of Oxford.
Funding: Supported by the Wellcome Trust and contributions from UCL’s Speech Communication Lab.
Source: Leighton Kitson, Durham University.
Image credit: NeuroscienceNews.com image adapted from Durham University materials.
Original research: “Distinct processing of ambiguous speech in people with non-clinical auditory verbal hallucinations” by Ben Alderson-Day, César F. Lima, Samuel Evans, Saloni Krishnan, Pradheep Shanmugalingam, Charles Fernyhough, and Sophie K. Scott, published in Brain, August 2017. doi:10.1093/brain/awx206
New insights into voice-hearers’ brain responses may lead to improved approaches for people who experience distressing voices. Image adapted from Durham University materials.
Durham University (2017). People Who Hear Voices Can Detect Hidden Speech in Unusual Sounds. NeuroscienceNews. Published August 21, 2017. Original research published in Brain.
Abstract
Distinct processing of ambiguous speech in people with non-clinical auditory verbal hallucinations
Auditory verbal hallucinations—hearing voices—are often linked to psychosis, but a minority of people in the general population experience them frequently without distress. Studying these non-clinical experiences provides an opportunity to isolate mechanisms specific to hallucinations without clinical confounds. Current theories suggest hallucinations arise from an imbalance between prior expectations and sensory input, but whether this affects auditory perception is unclear. In this study, twelve non-clinical voice-hearers and 17 matched controls underwent functional MRI while passively listening to degraded (‘sine-wave’) speech that was either potentially intelligible or unintelligible. Voice-hearers more often recognised the presence of speech before controls and before being informed of the stimuli’s intelligibility. Intelligible stimuli activated the expected left-lateralised speech network in both groups, yet voice-hearers showed stronger responses in dorsal anterior cingulate cortex and superior frontal gyrus, implicating greater involvement of attention and sensorimotor processes when speech was potentially intelligible. These behavioural and neural findings indicate that people who experience hallucinations without clinical disorder respond differently to meaningful auditory input. A relative weighting toward prior knowledge and expectation may produce non-veridical auditory experiences in some individuals, while also facilitating perception when prior knowledge helps decode ambiguous signals. These results align with predictive processing models of psychosis and have implications for understanding hallucinations across clinical and non-clinical populations.
Article: “Distinct processing of ambiguous speech in people with non-clinical auditory verbal hallucinations” by Ben Alderson-Day et al., Brain, August 2017. doi:10.1093/brain/awx206