Sakari Kallio

Hypnosis and the mind

The concept of hypnosis frequently appears in literature, comics, and films. Some think that hypnosis can induce individuals to experience or believe almost anything, or even connect with their subconscious mind, potentially curing any issue with a psychological basis. Conversely, some view hypnosis as mere folly, attributing its effects to belief and a desire to conform, arguing it lacks scientific credibility. My intrigue with hypnosis grew upon realizing that it has been a subject of scientific scrutiny for over two centuries. It was astonishing to discover that numerous pivotal figures in psychology and neurology had extensively studied and commented on hypnosis. Yet, its mention is conspicuously absent from many psychology textbooks.

When I delved into the scientific literature, I anticipated finding a clear definition of hypnosis and discerning which phenomena were factual versus those popularized in mediums like comics. To my surprise, no consensus existed among researchers regarding the definition of hypnosis. Over the past 50 years, new definitions have emerged approximately every decade, inevitably sparking debates cantered on a core question: can hypnosis be regarded as a kind of altered state of consciousness or whether the peculiar experiences and behaviour are the result of factors created by a strange social situation, such as heightened expectations, the desire to be a good subject, the conscious use of one's own imagination and even exaggeration of one's own experiences. Historically, the hallmark of responding to hypnosis has been the perception of events occurring automatically, without the intervention of imagination. However, many modern theories now define it as a deliberate and conscious action, although responses to certain motor suggestions appear to be automatic. According to this view, hypnotic hallucinations, for example, are never real but a deliberate use of imagination.

The ambiguity and mystique surrounding hypnosis piqued my interest, compelling me to delve deeper. I embarked on a dissertation, but it was only with the generous grant from the Gyllenberg Foundation that I could dedicate myself to it wholeheartedly, making my research endeavour feasible. Notably, prior hypnosis research in Finland hadn't evaluated the hypnotic susceptibility of participants and thus my initial move was to translate the Harvard Group Scale for Hypnotic Susceptibility, which is the most prevalent tool in research,[1] and establish suitable Finnish norms. Scales aiming to measure hypnotic susceptibility have been widely utilized since the 1970s to select participants for studies. Participants are rated based on their self-evaluation of their responses to specific suggestions, like suggestions that their hand is becoming so weighty that they can't raise it.

For an extended period, the dominant perspective in hypnosis research was that objective alterations in a participant's behaviour served as the sole and optimal metric for gauging hypnotic susceptibility. However, from my very first experiment,[2] I made it routine to interview participants post-hypnosis about their experiences and reactions to various suggestions. Their subjective descriptions underscored a significant revelation: even if two participants scored identically on a test, their personal experiences could vastly differ. For instance, one participant vividly described hearing music during the hypnosis session, believing it to be genuine, and was astonished upon realizing no music had been played. In contrast, another participant acknowledged hearing music "mentally", being fully conscious that there was no external source and recognizing it as an act of imagination. Both, however, confirmed hearing music during the experiment, albeit with divergent interpretations of the experience. Such disparities made me increasingly sceptical about the prevalent method of categorizing participants solely based on behavioural test scores.

I opted to concentrate my research primarily on subjects exhibiting high susceptibility to hypnosis, resorting to single-case designs when it was challenging to find multiple participants with closely matched responses. A significant portion of my studies revolved around a participant referred to as TSH, who demonstrated an ability to experience nearly all phenomena detailed in the scientific hypnosis literature. In fields such as neurology, it's entirely standard to delve deep into individual subjects to understand rare phenomena, leveraging a plethora of methods to obtain a holistic and precise comprehension of the subject matter.

Uniquely, I employed a method unexplored by other researchers at the time, which entailed toggling between hypnotic and non-hypnotic states using a single-word cue to both initiate and terminate the hypnotic state (a visual demonstration of this process is available for viewing). This instantaneous "Bing: you’re hypnotized" approach, reminiscent of a cartoonish hypnotiser, was designed to circumvent the potential exhaustion arising from the traditional hypnotic induction process that usually spans at least seven minutes. Through various methodologies, we ascertained that TSH's brain activity distinctly shifted during hypnosis and reverted to a standard waking state once the hypnosis was terminated, effectively "awakening" the participant from the hypnotic trance [3, 4]. This initial finding was further bolstered by subsequent results derived from transcranial magnetic resonance stimulation[5]

Arguably the most iconic representation of hypnosis, as popularized in films, books, and comics, is the distinct, almost trance-like gaze in the subject's eyes (as demonstrated in the video). Of course, this phenomenon has also been described in the scientific literature on several occasions and has been the subject of some preliminary research. I had previously observed that, under hypnosis, the demeanour of our subject, TSH, would undergo a noticeable transformation. Typically, animated and conversational, she would, upon hearing the trigger, become reserved and solemn, sitting motionless and gazing straight ahead, only acting upon specific prompts. Many theories postulate that this behaviour stems from the subject consciously adopting the role of a hypnotized individual, which subsequently manifests in their behaviour. Initially, I found this rationale plausible. However, upon conducting a study utilizing an electroencephalogram (EEG)[3], my confidence in this 'role-assumption' theory began to waver.

During the study, TSH was isolated in the EEG-room. A post-experiment review of the EEG data revealed an unexpected observation: in her hypnotized condition, TSH blinked approximately ten times less frequently than in the control condition. Given that she was alone during the experiment, it's perplexing to consider why she would feel compelled to 'play a role' and subsequently blink less, leaving this behaviour still somewhat enigmatic.

I sought the expertise of Professor Jukka Hyönä, head of the Psychology Department, and his then-assistant, Lauri Nummenmaa, to determine if the eye movement camera they employed in their research could shed light on the intriguing ocular phenomena observed in TSH. They proposed initiating the study with a standard set of automated eye movement tests, using the results to further tailor an experiment. The outcome was unexpected to all of us; it was evident from the final experiment that numerous automatic eye movements underwent alterations during hypnosis[6].

We also included 14 control subjects who were tasked with consciously replicating these eye movement changes – essentially, to emulate the behaviours of someone under hypnosis. These participants were provided with verbal descriptions of the desired changes and had the opportunity to view a video that displayed these altered movements. Yet, for most of the tasks, the control subjects were unable to voluntarily reproduce the changes, which reinforced the theory that hypnosis induces functional alterations in the brain, subsequently influencing the automatic and non-voluntary motor functions of the eyes.

A central debate among researchers revolves around whether hypnosis can unlock certain abilities otherwise unattainable in a regular state. The foundational argument of many theories asserts that any phenomena achieved through hypnosis can likewise be accomplished without it, contending that all observed effects are merely the product of a unique interactive context. Yet, some scholars posit that hypnosis can elicit automatic and profoundly realistic hallucinations, which individuals wouldn't be able to spontaneously generate in their typical waking state using, for instance, mere imagination.

This conundrum is similarly echoed in popular culture. Consider the common scenes in television hypnosis shows where a participant, under hypnosis, is suggested that they'll soon receive 'X-ray glasses' enabling them to peer through clothing. Upon donning these glasses, the participant's reactions often span surprise, embarrassment, and amusement, as though they genuinely perceive those around them in the nude. The crucial inquiry then becomes: what does the individual genuinely perceive? Is it feasible for someone under hypnosis to vividly hallucinate such scenarios? Or might they be amplifying and theatrically portraying their experience for the sake of entertainment?

The nature of hallucinations hypnotic hallucinations has always piqued my curiosity. In collaboration with Associate Professor Mika Koivisto, we embarked on a series of studies to determine the feasibility of entirely realistic and automatic hallucinations. While the annals of hypnosis research are replete with accounts of subjects experiencing vivid visual hallucinations, there's always the lingering doubt of potential exaggeration. We conducted several experiments and found a particular brain response that supported the idea that when a subject with TSH experienced a hallucination, it was accompanied by a corresponding change in the brain[7]. Nonetheless, I also aspired to explore the experience of hallucinations among a broader group of participants, without the necessity of brain activity monitoring devices.

After multiple attempts and in collaboration with docents Johanna Kaakinen and Mika Koivisto, we devised a colour vision test designed to be straightforward for those genuinely experiencing hallucinations, yet challenging to feign. Furthermore, the use of mental imagery intentionally in this context would be impractical because it would consume far too much time. Participants were initially tasked with swiftly and accurately vocalizing the colours of various symbols displayed on the screen, beginning from the top left (Figure 1a). Following a one-word hypnosis induction, they were given a suggestion that in the upcoming task, all circles would invariably appear red, all squares green, and all plus symbols blue. Subsequently, participants were presented with a new array displaying the same symbols, but this time, the circles, squares, and plus symbols were randomly assorted colours (see Figure 1b).

Figure 1. Example of symbol matrices presented to subjects in the control and experimental conditions. a) Initially presented to the participants, they were instructed to verbally utter the colours of the symbols swiftly, commencing from the top left, akin to reading a book. b) Displayed after the post-hypnotic suggestion, where participants were told they would observe a similar array of symbols; however, all circles would consistently appear red, all squares as green, and all plus symbols as blue. The task was again to utter the colours of the symbols quickly and accurately.

Figure 1. depicts two arrays that, if perceived according to the provided hypnotic suggestions, should appear identical and thus take an equivalent amount of time to utter the colours of the symbols. Following the experiment, participants were interviewed regarding their experiences.

A number of highly hypnotizable participants felt a disconnect between the colours they perceived and those suggested to them. For instance, they might have had a strong inclination that a green circle was red based on the hypnotic suggestion, yet they visually recognized it as green – its veridical colour. Remarkably, two participants perceived some or all of the symbols exactly as dictated in the hypnotic suggestion. For example, they visualized a blue square as green, in line with the provided suggestion. Eye movement data verified the authenticity of their experiences, eliminating that they feigned or exaggerated their experience. One participant was so deeply immersed in the experience that, even after being informed of the suggestion, she couldn't discern the symbol's true colour.

In contrast, control participants who attempted to mimic the performance of those genuinely experiencing colour hallucinations struggled, despite utilizing various strategies and imagination. They consistently failed to smoothly replicate the naming task, even when incentivized with a €50 reward for successful imitation[8]. You can test yourself by reading aloud the colours of the symbols in matrix a) and timing how long it takes. Then, for matrix b), do the same but remember to say "red" for each circle, "green" for each square, and "blue" for each plus sign.

From these experiments, one can infer that for a select few, the concept of "X-ray glasses" can indeed offer a genuine sensation of seeing through attire. However, for the majority, especially within the context of a performance, they are likely engaging and fully embracing their role as a "hypnotized" subject.

Taken together, my research paints a multifaceted picture of hypnosis. Some findings mirror the exaggerated phenomena popularized in comics like Donald Duck – the fixed stare, the "robotic" demeanour, and the vivid, realistic and automatic hallucinations. Conversely, for many, their altered behaviour under hypnosis might be akin to an actor immersing themselves in a role, embodying their character's experiences and actions. In sum, my studies suggest that hypnosis is a complex phenomenon that eludes a singular theoretical explanation.

With the backing of the Gyllenberg grant, I'm currently, together with professor Antti Revonsuo, developing a new version of the theory we co-authored in 2004 [9]. Our upcoming paper will critically assess the dominant theories of today, as well as the hypnotic suggestibility scales that have been utilized for over six decades. The crux of our argument hinges on the capabilities of contemporary information technology and consciousness research. We aim to delve into how these tools allow for an experimental exploration of individuals' actual experiences, and how such insights might shift the foundational beliefs of many existing theories.

Articles 2 through 6 and article 8 from the references were undertaken with the generous support of the Signe and Ane Gyllenberg Foundation.

1. Kallio, S. and M. Ihamuotila, Finnish norms for the Harvard Group Scale of Hypnotic Susceptibility, Form A. Int J Clin Exp Hypn, 1999. 47(3): p. 227-235.

2. Kallio, S., et al., Anterior brain functions and hypnosis: a test of the frontal hypothesis. Int J Clin Exp Hypn, 2001. 49(2): p. 95-108.

3. Kallio, S., et al., The MMN amplitude increases in hypnosis: a case study. Neuroreport, 1999. 10(17): p. 3579-82.

4. Fingelkurts, A.A., et al., Cortex functional connectivity as a neurophysiological correlate of hypnosis: an EEG case study. Neuropsychologia, 2007. 45(7): p. 1452-62.

5. Tuominen, J., et al., Segregated brain state during hypnosis. Neurosci Conscious, 2021. 2021(1): p. niab002.

6. Kallio, S., et al., The Existense of a Hypnotic State Revealed by Eye Movements. Plos One, 2011. 6(10 e26374): p. 1-7.

7. Koivisto, M., et al., A Preconscious Neural Mechanism of Hypnotically Altered Colors: A Double Case Study. Plos One, 2013. 8(8).

8. Kallio, S., M. Koivisto, and J.K. Kaakinen, Synaesthesia-type associations and perceptual changes induced by hypnotic suggestion. Scientific Reports, 2017. 7.

9. Kallio, S. and A. Revonsuo, Hypnotic phenomena and altered states of consciousness: A multilevel framework of description and explanation. Contemporary Hypnosis, 2003. 20(3): p. 111-164.

Associate professor of psychology

University of Turku

Professor of cognitive neuroscience,

University of Skövde, Sweden