– Sanne Brederoo, 9th December, 2020

PhD Student, Department of Psychology, University of Gronigen

“You’re saying you can hear your own thoughts in your head?!”, my friend exclaimed in surprise. I, in return, was astonished to learn that she can effortlessly conjure up a puppet in her mind’s eye and make it do a dance. It seems my friend and I differ strongly in terms of what goes on inside our minds: her visual imagery is very lifelike, while my auditory imagery is.

As it turns out, people vary strongly in terms of vividness of their mental imagery. We also know that hallucinations occur for some people, and not for others. This raises the question whether people who experience more vivid mental imagery, are also more likely to experience hallucinations. Research on this topic so far often focused on either the visual or the auditory domain, while of course underlying principles could be supramodal.

From previous studies we know that vividness of imagery is related to hallucination proneness, but cannot fully account for it. In addition to vividness, the misattribution of the internally generated experience to an external source seems to be a driving characteristic in hallucination proneness (Aleman et al., 2000; Brébion et al., 2008; Kanemoto et al., 2013; Mondino et al., 2015; De Boer et al., 2019). The more vivid the imagery, the more it will resemble externally based perception. As such, distinguishing it from perception, –reality monitoring, will become more difficult, but not impossible. 

This brings us to an additional candidate factor at play: in hallucinations, there is no or little feeling of control over the experience. This of course adds to the resemblance to genuine perception, as we have no control over that either. Back to mental imagery, vividness is not the only aspect that we can describe and on which people vary. Recall my friend who at will produced a puppet before her mind’s eye and choreographed a dance: she can be a perfect puppeteer of her own visual mental. For a person who lacks such control over the start, end, and content of mental imagery, the visual or auditory image may more readily come across as being externally based.

This led to our hypothesis that high imagery vividness in combination with low imagery control leads to increased hallucination proneness. Therefore, we tested this using online surveys (VVIQ and BAIS-V for visual and auditory imagery vividness; TVIC and BAIS-C for visual and auditory imagery control; NEVHI and LSHS-R for visual and auditory hallucinations), in the general population. 

The first pilot results (n = 45) show that people who have vivid visual imagery also tend to have vivid auditory imagery (r = .65, p < .001). I guess this makes my friend and me odd ones out. Likewise, people who experience strong control over their visual imagery experience strong control over their auditory imagery as well (r = .41, p = < .01). 

Importantly, a further result was that the more vivid the imagery, the more control over the imagery people experienced, in both the visual (r = .63, p < .001) and auditory (r = .61, p < .001) domains. This, of course, kept us from being able to test the hypothesis that high vividness in combination with low control leads to hallucination proneness: only very few participants in this sample showed those characteristics.

Nevertheless, we had an exploratory look at the characteristics of the occurrence of hallucinations in this sample from the general population. People experiencing low vividness and low control as well as people with high vividness and high control were amongst those that reported to have had hallucinations. This was the case for both the visual and auditory domains. Interestingly, of those people who had experienced visual hallucinations, some had enjoyed them (n = 6) while others had found them distressing (n = 3) or neutral (n = 2). What set those people apart was their ability to control the start, end, and/or content of their mental imagery. This hints at the possibility that being able to control your visual imagery helps you experience less distress from your visual hallucinations. Unfortunately, we didn’t include the necessary follow-up questions to delve deeper into a possible relationship between control over imagery and control over hallucinations.

We are currently expanding our sample and aim to include participants from a clinical population, hoping also to encounter more individuals who experience high vividness in combination with low control over their imagery. Although conclusions that we can draw from this first, small pilot-study are limited, I can imagine (vividly!) that future results will turn out informative regarding the origin and possible treatment of or coping with hallucinations in both the visual and auditory domains.

References

Aleman, A., Nieuwenstein, M. R., Böcker, K. B. E., & de Haan, E. H. F. (2000). Mental imagery and perception in hallucination-prone individuals. Journal of Nervous and Mental Disease, 188, 830-836.

Brébion, G., Ohlsen, R. I., Pilowsky, L. S., & David, A. S. (2008). Visual hallucinations in schizophrenia: Confusion between imagination and perception. Neuropsychology, 22, 383–389.

Kanemoto, M., Asai, T., Sugimori, E., & Tanno, Y. (2013). External misattribution of internal thoughts and proneness to auditory hallucinations: The effect of emotional valence in the Deese–Roediger–McDermott paradigm. Frontiers in Human Neuroscience, 7.

Mondino, M., Haesebaert, F., Poulet, E., Suaud-Chagny, M.-F., & Brunelin, J. (2015). Fronto-temporal transcranial direct current stimulation (tDCS) reduces source-monitoring deficits and auditory hallucinations in patients with schizophrenia. Schizophrenia Research, 161(2–3), 515–516.