Q. What are voices?
A. Hearing voices and other sounds are auditory perceptions that are experienced in the absence of corresponding external acoustic stimuli.
They can be whistles, bangs, clapping, screams, ticks, voices producing intelligible or unintelligible speech, and music (instrumental, singing, or both).
Sometimes certain external sounds will result in, or trigger, voices. However, in this case the voice is different from the external acoustic stimulus.
The psychologist Richard Bentall defines hearing voices, visual, olifactory, taste and other perceptions that:
- lack an external stimulus have the full impact of an actual perception
- are not under voluntary control
These perceptions have been reported to occur for all five senses.
Q. What is happening when people hear voices?
A. It appears that the auditory system plays a fundamental role in hearing voices. Since people who hear voices perceive sound in some form, the perceptual mechanism for sound is be ingactivated, at least in part, in a similar fashion as when one hears external acoustic stimuli. Although sound waves are not associated with what a person with voices hears, the person does perceive sound nonetheless. Evidence for this has come from functional imaging techniques such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), along with sophisticated audiological techniques. These techniques have shown that the central auditory system activity is related to hearing voices.
Q. What about voices coming from inside or outside of the head?
A. There are two definitions from psychiatry relating to voices that could be confused. One is the difference between so called “pseudohallucinations” and “true hallucinations”.
Pseudohallucinations have been referred to as sounds perceived inside the head that have no correlation to the outside world, while true hallucinations are considered to be actual perceptions that have an association with the external or objective environment. However, studies by Oulis et al. and Copolov et al. showed there was a mixture of pseudo- and true hallucinations in a large number of people who hear voices and concluded there was little value in differentiating true from pseudohallucinations.
Q. Are there other causes for hearing voices?
A. The other term that could easily be confused with ahearing voices is tinnitus. Tinnitus can be an auditory perception without an external stimulus and, therefore, could be considered to be a type of voice. However, tinnitus is often a humming, tonal-type sound of any pitch and, in some cases, more than one pitch. Although, tinnitus can also be a pulsing, clicking, or frying (noisy) type of sound. It may be subjective (i.e., only the person with the tinnitus can hear it) or objective (i.e., others can hear it). One way hearing voices can also be distinguished from subjective tinnitus in that tinnitus is seldom heard as voices, speech, music, or songs.
Q. How many people hear voices?
The prevalence of hearing voices is greater than one might expect. In a sample of 18,572 community residents above 18 years of age, between 2% and 3% said they had experienced voices (Tien Y: Distributions of hallucinations in the population. Social Psychiatry Psychiatric Epidemiol 1991;26:287–292). In this study voices occurred more often in women than in men and prevalence increased with age. A study focusing on the prevalence of hearing voices in the elderly reported that 32.8% of this age group had experienced hallucinations. (Cole MG, Dowson L, Dendukuri N, Belzile E: The prevalence and phenomenology of auditory hallucinations among elderly subjects attending an audiology clinic. Int J Geriatric Psychiatry 2002;17(5): 444–452). Later studies have found the reported incidence of hearing voices in the general population of between between 4 – 7%