The role of alcohol in expectancy-driven mystical experiences: a pre-registered field study using placebo brain stimulation

ABSTRACT

We explored the effects of alcohol on expectancy-driven mystical and quasi-mystical experiences by manipulating participants’ expectations. By using the so-called God Helmet suggestion, participants were led to believe that a placebo brain stimulation could elicit mystical experiences. In this pre-registered field study, we set out to test whether alcohol could increase participants’ susceptibility to the God Helmet suggestion in a large sample (N = 193) at a Dutch festival. Participants reported a wide range of extraordinary experiences associated with mysticism, including out-of-body experiences, involuntary movements, and the felt presence of invisible beings. Regression analyses revealed that self-identified spiritualism predicted extraordinary experiences, but neither objective nor subjective measures of alcohol intoxication increased participants’ susceptibility to the God Helmet. Methodological limitations that may explain the lack of an effect for alcohol are discussed, while we explore the usefulness of the God Helmet in the study of extraordinary experiences.

KEYWORDS:

• God Helmet
• alcohol
• expectancy
• suggestibility
• executive function
• mystical experiences

The sway of alcohol over mankind is unquestionably due to its power to stimulate the mystical faculties of human nature … – William James (1902/1985, p. 307)

Introduction

Psychoactive substances have been frequently used in the context of religious rituals (de Rios & Winkelman, 1989; Ellens, 2014; Fuller, 2000). For instance, in many indigenous religions in the Peruvian Amazon, tribes use ayahuasca during religious ceremonies to get into contact with ancestor spirits (McKenna, 1999; Tupper, 2009). One specific psychoactive substance that has received little attention in the context of religious rituals is alcohol. Alcohol has been consumed by humans for several thousands of years (McGovern, 2013), and the link between alcohol and religion is well documented but complex (Boyle, 2013; Dietler, 2006; Fox, 2000; Hanson, 1995). In some cultures, the ritual experts use alcohol as part of their rituals, while other religions allow alcohol to be consumed by the ritual participants (e.g., Catholic Christians, Native Americans, and the ancient Greeks, Hindus, Jews, and Chinese). Several sects of religions restrict alcohol use (e.g., Protestant Christians and Buddhists), while other religions prohibit the use of alcohol altogether (e.g., Islam and Jainism; Dietler, 2006; Royce, 1985).

The specific effects of alcohol consumption in religious rituals are poorly understood. Some researchers have proposed that alcohol fosters social cohesion among participants (for reviews, see Kuntsche, Knibbe, Gmel, & Engels, 2005, 2006), while others suggest that alcohol could facilitate extraordinary religious experiences (James, 1902/1985; Smith, 1964). This latter idea is particularly interesting because extraordinary experiences in rituals may reinforce participants’ belief in supernatural worldviews (James, 1902/1985). It could be, for instance, that in the right suggestible ritual context, alcohol intoxication facilitates mystical and quasi-mystical (i.e., extraordinary) experiences. Alternatively, ritual experts such as shamans and witch doctors may benefit from the liberating and mind-altering effects of alcohol as they often display interactions with the supernatural realm following alcohol consumption. Alcohol may also enable ritual spectators to be less critical when they witness supernatural events suggested to them by ritual leaders (e.g., spirit travels or communication with deceased ancestors). Stories about such events are likely to spread quickly and thereby foster endorsement of supernatural beliefs¹ (Blackmore, 1999; Hardy, 1979; James, 1902/1985; Lang, 1900). Ideas about the potential involvement of alcohol in fostering extraordinary experiences, however, have remained hypothetical. In fact, it remains unclear if and to what extent alcohol can facilitate extraordinary experiences at all.

William James was one of the first to describe a link between alcohol and extraordinary religious experiences (1902/1985, p. 307), but he did not describe the potential underlying mechanism through which alcohol could exert its effects. Modern scientific evidence hints at two potentially interrelated causal pathways from alcohol to extraordinary experiences: by impaired executive functioning and by increased suggestibility.

Alcohol, executive function, and increased suggestibility

Alcohol affects the information-processing capacities of the brain (e.g., Bjork & Gilman, 2014), including motor control, which is subserved by the primary/supplementary motor areas, the basal ganglia, and the cerebellum. Alcohol also affects the motivational processes, mediated by the ventral striatum and the nucleus accumbens, and a host of executive functions supported by the dorsolateral prefrontal cortex (DLPFC) and the anterior cingulate cortex (ACC; for a review, see Bjork & Gilman, 2014). Alcohol reliably impairs basic executive functions like attentional control, motor control, working memory, and inhibitory control (Zoethout, Delgado, Ippel, Dahan, & van Gerven, 2011).

The effect of alcohol on the brain’s executive processing is interesting because impaired executive functioning has been associated with increased suggestibility (for a review, see Parris, 2017). Suggestibility is the extent to which people are influenced by suggestions, such as the suggestions of a hypnotist or shaman. Suggestibility seems to be increased through alcohol consumption (e.g., Van Oorsouw, Merckelbach, & Smeets, 2015). Although the general effects of alcohol and psychoactive substances differ strongly, there are some indications that the effects of alcohol on suggestibility may be at least somewhat similar to psychoactive substances such as lysergic acid diethylamide (LSD; Carhart-Harris et al., 2015; Sjoberg & Hollister, 1965; Weitzenhoffer, 1980), mescaline (Weitzenhoffer, 1980), and nitrous oxide (Whalley & Brooks, 2009). For example, alcohol-intoxicated participants seem more prone to follow leading questions (Van Oorsouw et al., 2015), and alcohol consumption appears to increase participants’ susceptibility to hypnotic suggestions (Semmens-Wheeler, Dienes, & Duka, 2013). However, the literature on alcohol and suggestibility is scarce, and some studies show no effect (Dienes et al., 2009) or even a negative relationship (Santtila, Ekholm, & Niemi, 1999). Based on the evidence presented above, alcohol may impair the brain’s executive processing to the extent that people become more susceptible to the suggestions by ritual leaders, and this may facilitate extraordinary experiences in participants of rituals. Yet empirical support for this possible relation between alcohol and mystical experiences is still missing.

Suggestion, beliefs, and the God Helmet

The power of suggestion has recently been explored in a series of studies that use both verbal and contextual suggestion to elicit extraordinary experiences (Andersen, Schjoedt, Nielbo, & Sørensen, 2014; French, Haque, Bunton-Stasyshyn, & Davis, 2009; Granqvist et al., 2005; Granqvist & Larsson, 2006; Tinoca & Ortiz, 2014; van Elk, 2014). One particularly suggestive manipulation for eliciting extraordinary experiences is the so-called God Helmet suggestion. The God Helmet suggestion is a placebo brain stimulation manipulation combined with sensory deprivation, which generates strong expectations in participants who are instructed that the helmet stimulates their brain electromagnetically to elicit various types of extraordinary experiences. The God Helmet was originally designed to test the effects of weak electromagnetic transcranial brain stimulation on paranormal experiences (Persinger, Tiller, & Koren, 2000; Pierre, & Persinger, 2006), but the transcranial effect of the device is highly controversial (Granqvist et al., 2005). Despite this controversy, the placebo brain manipulation itself has proven to be an effective and powerful tool for manipulating participants’ expectancies to elicit extraordinary experiences (Andersen et al., 2014; Granqvist et al., 2005; Maij & van Elk, in preparation; van Elk, 2014; van Elk, in preparation).

The placebo brain stimulation effects induced by the helmet may best be understood in light of the predictive processing framework (Andersen et al., 2014; Büchel, Geuter, Sprenger, & Eippert, 2014; Schjoedt et al., 2013; van Elk & Aleman, 2017). According to proponents of this framework, lifelong interactions with the environment result in models with which the brain tries to predict what sensory input it can expect (Clark, 2013; Friston, 2005; Friston & Kiebel, 2009). The brain’s predictions are compared to sensory input, and detection of mismatches between predictions and sensory input (i.e., prediction errors) are used to correct and update predictive models. The God Helmet may induce strong predictions about extraordinary experiences, while sensory deprivation may prevent participants from updating their models based on sensory input (see Figure 4 in the supplementary material for a schematic representation of the working of the God Helmet in terms of predictive processing). With limited access to sensory information, randomly fluctuating bodily sensations and internal thoughts may be interpreted in light of the kind of experiences predicted by the God Helmet suggestion.

Importantly, the God Helmet suggestion appears to be most effective for people who already believe in the possibility of having the kind of experiences suggested to them by the experimenter. For example, spiritualists seem particularly prone to suggestions about so-called “felt presence experiences” because they believe in the possibility of connecting with spirits, while New Age practitioners seem more prone to experience holistic experiences (Andersen et al., 2014; Granqvist & Larsson, 2006). The least susceptible participants either reject the possibility of a supernatural realm, or simply remain skeptical of the suggestions made about the God Helmet. Whether alcohol can strengthen the power of the God Helmet suggestion by reducing skepticism is therefore an interesting question.

Based on previous findings, we set out to test whether alcohol consumption (measured objectively and subjectively) predicted increased susceptibility to expectancy-driven mystical experiences (self-report measures of extraordinary experiences and frequency of experiences), by using placebo brain stimulation, while controlling for demographics (i.e., gender, age, and education) and cultural learning (i.e., whether participants themselves or their parents were supernatural believers). We adopted a correlational approach, so no control group was included intentionally. The specific aim was to investigate whether susceptibility to the God Helmet suggestion increases with alcohol consumption, to examine if such a correlation might be mediated by impaired executive processing (i.e., performance on a Stroop Task), and to see if we could replicate whether self-identified spirituality is predictive of such experiences (e.g., Andersen et al., 2014). Briefly, we set up a controlled environment for the God Helmet suggestion at a large Dutch festival² and managed to recruit a sample of 199 participants who all received the same instructions and suggestions. All our hypotheses, materials, and data analysis plans were pre-registered on the Open Science Framework (see https://osf.io/7u4wd/ and supplement https://osf.io/4m7n2/).

Methods and materials

Participants

Participants were recruited at Lowlands, a large three-day Dutch music festival with over 50,000 visitors and a stage dedicated to science (i.e., Lowlands science). The study was advertised in the program booklet as “Tripping with the God Helmet: Researchers of the University of Amsterdam will electromagnetically stimulate your brain to elicit spiritual experiences.” By conducting the study at a festival, we expected to observe variation in alcohol intoxication as well as in the types of worldviews people hold (i.e., spiritualists and skeptics). In total, 199 participants started the study. Six participants did not complete the study due to a variety of reasons (e.g., some participants took the helmet off after several minutes as they did not notice anything). Of the 193 participants who completed the study, 61.7% were male (n = 119) and the mean age was 26.2 years (SD = 9.6, range = 18–69). Participants were generally highly educated (41.7% pre-university or university, 38% senior general secondary education or college, 15.6% lower secondary education or vocational education college, 4.7% other). People participated voluntarily and were not compensated. However, to increase the response rate on a follow-up questionnaire, we did reward two participants with festival tickets for the upcoming year by means of a lottery. The ethics committee of the University of Amsterdam approved the experimental protocol, all participants signed written informed consent, and all participants were treated in accordance with the Declaration of Helsinki.

Procedure

Upon arrival at the science booth, participants were screened on the inclusion criteria. Participants read an information voucher in which the supposed working of the God Helmet and other aspects of the study were explained (see supplementary material). Subsequently, objective alcohol intoxication was measured by means of an alcoholmeter, and a sticker was attached to the participant’s shirt with an anonymous participation number and their blood alcohol (BAC) level.

Once participants were seated in an open cubicle behind a laptop (see Figure 1 of the supplementary material), they were required to fill out their demographic information and questions related to their religiosity and spirituality on a computerized survey. After these questions were completed, participants viewed a video in which the working of the helmet was explained. Next, the Stroop Task was explained, both verbally and with text on the computer screen. As soon as the Stroop Task was completed, an experimenter placed the God Helmet on the participant’s head and attached the participants to sham electrophysiological measures (i.e., apparatus that were not turned on), supposedly to keep track of their health. Their fingers were attached to a sham skin conductance apparatus and heart rate stickers and wires were attached on their breast under their shirt. Participants were provided with blindfolds, earphones with white noise and were given a response key (i.e., mouse button) to indicate with their index finger whether and when they had an extraordinary experience. After 15 minutes of sitting with the God Helmet, the helmet was taken off and the blindfolds and earphones were removed as well. Participants were asked to fill out questions on the laptop relating to the type of experiences they had had. In the final comment of the questionnaire, participants were asked to fill out their email address so we could send them the debriefing as well as some follow-up questions. Follow-up questions were sent within five days after the festival. A debriefing was sent by mail two weeks after the experiment, to prevent the debriefing influencing the follow-up questions via (social) media exposure.

Testing site

It is important to note that organizational rules of the festival limited us to test the participants for a maximum of 45 minutes. Therefore, tasks and measures were used that took relatively little time, and only relevant items of existing scales were selected. In addition, although there was a specific stage dedicated to conducting scientific studies, the experimental conditions were suboptimal for the experimental procedure. The bass sound of a nearby stage could occasionally be heard, there were no closed cubicles, and the wooden floor moved if people walked nearby. These distractions inevitably had an effect on the participants (see the Results section [“Nature of Experience”] and Discussion for more details). We made use of six open cubicles with experimental equipment, so that six participants could be tested simultaneously (see Figure 1 in the supplementary material for a schematic representation of the testing site).

Suggestibility manipulation

A placebo brain stimulation suggestion was used to manipulate participants’ expectations. The helmet was a transformed metallic-colored skate helmet with wires attached to the back of a bogus analog to digital-box which had a flickering light (see Figure 2 in the supplementary material), but the helmet was not attached to any electrical generator. The credibility of the helmet manipulation was increased in five ways. First, participants were screened on four exclusion criteria: (1) epilepsy; (2) easy fainting; (3) claustrophobia; and (4) any form of brain damage. Second, prior to the study, participants read a short review of research claiming that the helmet reliably elicits extraordinary experiences (e.g., Persinger et al., 2000; Pierre & Persinger, 2006; the full instructions can be found in the supplementary material). Third, prior to the study, participants watched a YouTube video of the Big Think (a YouTube channel in which science topics are discussed). In this video, author Steven Kotler explains how the helmet (supposedly) works (i.e., by means of electromagnetic stimulation) and describes the types of experiences that can be induced through the helmet.³ Fourth, sham electrophysiological measures (i.e., skin conductance and heart rate) were used and we told participants that these were included to “keep track of their health.” Fifth, a vomit bowl was placed on every table (see Figure 3 in the supplementary material for a picture of the experimental set-up). To decrease bottom-up sensory input, participants were sensory deprived by means of an eyeshade and they listened to white noise presented with in-ear earphones. To see if the manipulation raised suspicion, at the end of the experiment we asked participants to describe the side effects they experienced as a result of the stimulation with the helmet (for a similar procedure, see Andersen et al., 2014).

Measures

Nature of the experiences. The nature of the experiences was measured by asking participants what they experienced when they pressed the button – if they pressed it at all. To categorize the reported experiences, we classified all comments in a categorization scheme. First, all comments were read by one of the authors (DLRM) and a categorization scheme was proposed to a second author (MvE). The second author categorized half of the subjective reports on the basis of the categorization scheme and proposed some small adjustments. Subsequently, the first author tried to classify the comments on the basis of the renewed categorization scheme and some final adjustments were made. This resulted in eight types of reported experiences, which are presented in Table 1, and are accompanied by the inter-rater reliabilities and the frequency with which they were reported. The reliabilities indicate that we agreed to a sufficient extent on the categorization of the different types of experiences.

Extraordinary experiences. Frequency. To measure the frequency of extraordinary experiences, participants had to press the mouse button each time they felt “something extraordinary” during the 15 minutes that they wore the helmet. This task was programmed and responses were recorded using Presentation software (V.16.2, Neurobehavioral systems, Albany, CA, USA).

Intensity. The intensity of extraordinary experiences was measured by a subjective rating question at the end of the 15-minute stimulation (“To what extent did you feel a mystical/spiritual experience as a result of the helmet?” 0 = not at all, 100 = very much), combined with a shortened version of the mysticism scale (items 1, 9, 16, 22, 23, 25, 28, and 29; Hood, 1975), statements to which participants could agree or disagree. Based on previous work on the God Helmet (Andersen et al., 2014; Granqvist et al., 2005; Granqvist & Larsson, 2006), two additional items were included. One referred to the feeling of awe (i.e., “The helmet left me with a feeling of awe”); another referred to the feeling of a presence (i.e., “I felt the presence of another being”).

Alcohol and drugs. Objective alcohol measure. Alcohol intoxication was objectively measured with a calibrated alcoholmeter (Alcoholtester Alcoscan ALC-1) – the manufacturer appoints the accuracy between 0.005% BAC and 0.050% BAC. BAC is the blood alcohol concentration content. A BAC of 0.1% means that there is 0.1 gram of alcohol for every liter of blood. Mild euphoria and concentration problems start at around 0.03% BAC; disinhibition and reasoning problems start around 0.06% BAC; possibility of nausea and motor control problems start above 0.1% BAC (Carp, 2015).

Subjective alcohol and drug measure. Apart from objective alcohol intoxication, we measured the subjective index of their “high” (Zoethout et al., 2011), by letting people indicate on a scale from 0 (completely sober) to 100 (very high) how drunk they felt from alcohol. Participants were also asked how many units (i.e., glasses or cups) of alcohol and other types of drugs (to rule out effects of other intoxicants; see supplementary material) they had consumed on that day (i.e., since they were awake) on a scale from 1 to 20. Unfortunately, due to a programming error, these subjective questions were not seen by the participants and had to be obtained retrospectively, in a follow-up questionnaire.

Executive functioning. A Stroop Task was used as a proxy of inhibitory control, which is part of the executive functioning processes (Mansouri, Tanaka, & Buckley, 2009). The task was derived from the Millisecond Software LLC⁴ website, which provides an online database with cognitive tasks. The task was an adapted version of the one designed by Bauer and Cox (1998). In this task, words or squares were presented in four different colors (red, green, blue, and black). Participants had to indicate the color of the ink of the word or square by pressing one of four keyboard keys (d, f, j, or k for respectively the colors red, green, blue, and black). In congruent trials, the color of the ink was consistent with the meaning of the word (e.g., the word “blue” written in blue ink). In incongruent trials, the color of the ink was inconsistent with the meaning of the word. Therefore, participants had to inhibit an automatic behavior (i.e., reading). In control trials, a square with a color was presented. In the task, 94 trials were presented. The first 10 were practice trials so participants could get acquainted with which keyboard button corresponded to which color, and this information was also presented during each trial at the top of the screen. The remaining 84 trials consisted of 12 different possibilities (i.e., 4 colors × 3 conditions) each presented seven times. Each word was presented in the middle of a white screen and was presented for as long as the participants waited to respond. For incorrect answers, a red cross was presented on screen for 400 ms. No feedback was given for correct trials. Between trials, a 200 ms white screen inter-stimulus interval was presented. As a measure of response inhibition, we subtracted the reaction time of the incongruent trials from the reaction time of the congruent trials (Bauer & Cox, 1998). We did not pre-register outlier criteria and none of the trials were deleted.

Spirituality and religiosity. Spirituality and religiosity were measured with the following questions with scales ranging from 0 (not at all) to 100 (very much). “How religious do you consider yourself?” and “How spiritual do you consider yourself?”

Spirituality and religiosity of the parents. Participants who were brought up surrounded by credibility-enhancing displays of a supernatural realm (Henrich, 2009; Lanman & Buhrmester, 2017) might be somewhat more open to the idea of supernatural experiences than participants without such upbringing. We addressed this issue with the following question ranging on a scale from 0 (not at all) to 100 (very much). “How religious and/or spiritual do you consider your parents/caretakers? (If you consider one of them very religious/spiritual but the other not at all, opt for 50).”

Exploratory measures. We piloted physiological measures of skin conductance and heart rate variability in two out of six participants. However, response variability was overly sensitive to testing conditions and could not be used.

Data analysis

The nature of the experiences was described in a qualitative manner and the frequencies were reported. To predict the frequency of extraordinary experiences (i.e., the number of button presses), we used generalized linear models (GzLM). Considering that the count data followed a Poisson distribution with zeros, we used a negative binomial regression model (Zeileis, Kleiber, & Jackman, 2008). As predictors, gender, age, education, religiosity, spirituality, religiosity of the parents, objective alcohol intake, and response inhibition were inserted. To predict the intensity of the extraordinary experiences, we used hierarchical linear regression (HLR; Method = Enter). To combine the data of the subjective intensity item and the mysticism scale items, we used principal axis factoring (PAF) analyses with oblique (Promax) rotation (Russel, 2002). The regression weights were used as a combined measured of intensity of the experience. In the first step of the HLR, we controlled for gender, age, and education. As predictors, religiosity, spirituality, religiosity of the parents, objective alcohol intake, and response inhibition were used.

As outlined above, we treated the analyses in which we used retrospective subjective alcohol intoxication separately. Thus, we had two additional models for the retrospective follow-up data: one additional GzLM for the frequency of the extraordinary experiences, and one additional HLR for the intensity of the extraordinary experiences. The only addition was that the subjective alcohol intake measures (i.e., feeling “high” and units consumed) were also included. Data pre-processing, principal axis factoring, and the HLRs were run in R Studio (R Core Team, version 1.0.136). All other analyses were run in SPSS (IBM, version 23).

Results

Alcohol and drugs data

Of all participants, 73.2% consumed alcohol on the day of testing, 16.8% consumed alcohol and at least one other type of drug on the day of testing, 7.4% did not consume alcohol or drugs, and 2.6% used at least one type of drug without consuming alcohol.

Nature of experience. The entire study depends on the possibility of eliciting the kind of experiences that are of interest to the study of religion. We therefore start by quoting examples of the striking experiences reported by the participants before we reduce these reports to types and frequencies in our classification schema (below).

Participant a:

“It felt as if I was floating, as if I was no longer on the chair.”

Participant b:

“I had the feeling that the helmet was taking control over me. My head started turning around and my eyes were spinning.”

Participant c:

(this text is shortened and paraphrased) “I went into a dialogue with a dark circle, it sounded like my own voice yet also different. It was something ‘higher.’ The voice told me that I was ready to get children, even though the circumstances were suboptimal. Deep down I already knew this and I became very emotional and started crying, but I was never afraid. I have never had such an experience, it was truly amazing.”

Participant d:

“I came loose from the chair, the chair fell and I was floating. The desk started to shake heavily and I felt the presence of a dark figure next to me. It whispered something in my ear that I could not understand.”

Participant e:

“A strong gravitation or magnetic force was pulling my head back. I wanted to move my head back but it was simply impossible.”

Participant f:

“Some force wanted to let me know its presence and let me click the button.”

Participant g:

“‘It felt as if I was floating, like being slowly lifted. My heart slowed down and my breathing sometimes stopped, because of the floating feeling – similar to an MDMA experience. I felt stable and after a while it seemed like an external influence was affecting me. By brain heated up and I felt tingling sensations over my body and I got a pleasant goosebump feeling.”

Table 2 indicates that participants reported weak bodily sensations most frequently, but several participants reported strong bodily sensations, and distractions and skepticism were also relatively frequently reported. Time and space distortions were not reported often. The type of experiences covered by the different categories become apparent from Table 3, in which the sub-categories are also reported, in association with the frequencies with which they occur. Certain categories warrant some more detailed explanation. By “memories of past drug experience,” we mean that participants sometimes reported that their experiences were comparable to those of earlier drug experiences (e.g., with psychedelics, such as MDMA, LSD, or magic mushrooms). By “ego dissolution,” we mean that participants reported that they felt as if their soul or spirit was slowly dissolving and that they felt no longer present. By “moving surroundings,” we mean that participants reported movements of objects in the environment, such as a shaking desk or chair. By “forces,” we mean that participants reported that they noticed the influence of certain forces, such as the feeling of being pushed or pulled, that gravity changed, or that they noticed the presence of energies or electricity. By “feeling of oneness,” we mean that participants reported feeling “one” with the universe or with other beings.

Table 1. Inter-rater reliability scores and average number of occurrences of the categorization scheme categories.

	κ	N	%
Auditory	0.87	30.3	16.1
Visual	1	27.5	14.6
Mental	0.74	24	12.8
Weak bodily sensations	0.87	147.5	78.5
Strong bodily sensations	0.67	56.5	30.1
Events in surrounding	0.78	38.5	20.5
Time/space distortion	0.78	10.5	5.6
Distraction/skepticism	0.81	57	30.3

Note: κ = Cohen’s Kappa; N = the average number of occurrences for the two raters; % = the average number of occurrences expressed in percentages; N/188.

Table 2. Categorization scheme with frequency of occurrences per category and sub-category.

Category	Sub-category	N	%
Auditory	1. Agent voices	21.5	11.9
	2. Music/melody	17.5	9.7
	3. Other sounds	15.5	8.6
Visual	1. Flashes/light/light at end of tunnel	13	7.2
	2. Imagery/visuals/objects	22.5	12.5
	3. Agents/people/shadows	14	7.8
Mental	1. Feelings/emotions	5	2.8
	2. Self-referential processing	6	3.4
	3. Mind-wandering	4	2.2
	4. Memories of past drug experiences	9	5.0
Weak bodily sensation	1. Cold/shivering/goosebumps	7	3.9
	2. Itch/tingling/light pain	41	22.8
	3. Stress/heart rate increase/hot/sweat	29	16.1
	4. Light touches	10.5	5.8
	5. Dizziness	22.5	12.5
	6. Sleepiness/relaxation	37.5	20.8
Strong bodily sensation	1. Involuntary movements	18	10.0
	2. Out-of-body/floating	15.5	8.6
	3. Ego dissolution	6.5	3.6
	4. Paralyzed	4	2.2
	5. Heavy arms/legs/head	12.5	6.9
Events in surrounding	1. Feeling of a presence	10	5.6
	2. Moving surroundings	8	4.4
	3. Forces	20.5	11.4
Time/space distortion	1. Time distortion	3.5	1.9
	2. Space distortion	4	2.2
	3. Feeling of oneness	3	1.7
Distraction/ skepticism	1. Distraction	25	13.9
	2. Doubts about helmet	9.5	5.3
	3. Felt bored	5.5	3.1
	4. Nothing happened	17	9.4

Note: N = the average number of occurrences for the two raters; % = the average number of occurrences expressed in percentages; N/188.

As can be seen in Table 3, randomly fluctuating bodily sensations such as itches and tingles, sleepiness or heart rate increases were most frequently reported. Of the extraordinary experiences, agent voices, involuntary movements, forces, floating, and out-of-body experiences were reported relatively frequently.

As we hypothesized that alcohol could facilitate extraordinary experiences by reducing executive functioning, we analyzed the relationship between alcohol and performance on the Stroop Task. The correlations between performance on the Stroop Task (i.e., response inhibition) and the objective as well as subjective alcohol measures are provided in Table 4. Although two out of three alcohol measures were statistically significant correlated to response inhibition, the correlations were weak.

Table 3. Correlation table for the relationship between alcohol and response inhibition performance of the Stroop Task.

	1. Alc obj	2. Alc subj1	3. Alc subj2	4. RI
	(N = 193)	(n = 138)	(n = 138)	(n = 187)
1.	–	.58*** (n = 138)	.43*** (n = 138)	−.18* (n = 187)
2.		–	.27** (n = 138)	.09 (n = 138)
3.			–	−.20* (n = 138)
4.				–

Note: * p < .05, ** p < .01, ***p < .001; Correlations represent Pearson correlations; Alc obj = blood alcohol concentration in percentages as measured with the objective alcohol meter; Alc obj = blood alcohol concentration in percentages as measured with the objective alcohol meter (range = 0–2); Alc subj1 = subjective alcohol units consumed (range = 0–20); Alc subj2 = subjective alcohol high (range = 0–74); RI = response inhibition.

Retrospective data

Of the 138 participants (69.3% response rate) who started the follow-up survey, six could not be linked to the first data collection because they filled in a different email address from the first time. Therefore, we had 130 participants for the frequency of extraordinary experiences (i.e., the number of times participants pressed the button) and 132 participants for the intensity of extraordinary experiences (i.e., the combination of the subjective rating of the intensity and the mysticism scale items). To investigate the consistency between the festival data and the retrospective data, we looked at the only question that occurred in both questionnaires (besides the email address), which was whether participants had used alcohol, drugs, a combination thereof, or neither. A reliability analysis indicated that the participants were fairly consistent in their responses, Cronbach’s alpha (α) = .82. Specifically, 12 participants filled in a different answer from before. Although speculative, it may be the case that they could not specifically remember on which of the three festival days they participated in the study.

Missing data

Data on the Stroop Task were missing for seven participants, and data on the response button task were missing for three participants due to computer failure (if the battery cable was touched slightly, the laptop turned off). Table 1 shows the descriptive statistics of the measures included in the regression models. In general, participants were not very religious but did consider themselves to be somewhat spiritual, and their parents were also considered somewhat religious. Alcohol intake was relatively low; the average score was indicative of “mild euphoria and concentration problems” (Carp, 2015).

Table 4. Descriptive statistics of the measures included in the regression models.

	Frequency	Intensity S	Intensity M	Alc obj	Alc subj1	Alc subj2
N	196	193	193	193	138	138
M	4.1	20.3	1.5	0.30	3.9	17.4
SD	7.8	25.3	1.7	0.34	3.4	20.0

Table 4. Continued.

	RI	Religiosity	Spirituality	Parents
N	192	193	193	193
M	176.6	15.2	39.4	37.1
SD	595.0	20.3	26.7	28.9

Note: N = number of cases; M = mean; SD = standard deviation; Frequency = frequency of extraordinary experiences; Intensity S = intensity of the extraordinary experiences as measured with the single mystical intensity slider (range = 0–100); Intensity M = average score on the mysticism scale items (range = 0–8); Alc obj = blood alcohol concentration in percentages as measured with the objective alcohol meter (range = 0–2); Alc subj1 = subjective alcohol units consumed (range = 0–20); Alc subj2 = subjective alcohol high (range = 0–74); RI = response inhibition; Parents = religiosity/spirituality of the parents (range = 0–100).

Extraordinary experiences

Frequency of extraordinary experiences. Generalized linear models. The outcomes of the GzLMs for predicting the frequency of extraordinary experiences as measured using the number of button press responses of both the models with (GzLM1) and without the retrospective data (GzLM2) can be found in Table 5. A correlation table of the predictors included in the model can be found in the supplementary material (Table S2). The model without retrospective data explained statistically significantly more of the variance than an intercept only model, χ²(15) = 41.17, p < .001, Log-likelihood = −850.94. Both education and spirituality were statistically significant predictors. Specifically, an increase in education from lower general secondary education to higher general secondary education was associated with a decrease in the frequency of extraordinary experiences. Importantly, an increase in spirituality was associated with an increase in the frequency of extraordinary experiences, but objective alcohol intoxication was not associated with the frequency of extraordinary experiences.

Table 5. Generalized linear models for predicting the frequency of extraordinary experiences.

GzLM1	b	SE b	p	GzLM2	b	SE b	p
Constant	2.16	0.53	<.001***	Constant	2.25	0.71	.002**
Gender2	0.07	0.25	.778	Gender2	0.01	0.30	.979
Age	−0.03	0.02	.056	Age	−0.04	0.02	.047*
Alcohol obj	−0.03	0.36	.929	Alcohol obj	0.12	0.59	.845
Education2	−0.86	0.35	.014*	Education2	−1.30	0.44	.003**
Education3	−0.54	0.34	.113	Education3	−0.80	0.43	.064
Education4	0.43	0.67	.522	Education4	0.49	0.77	.524
Religiosity	0.01	0.01	.170	Religiosity	0.01	0.01	.389
Spirituality	0.01	0.01	.034*	Spirituality	<.01	0.01	.409
Parents	<.01	<.01	.529	Parents	0.01	0.01	.131
RI	<.01	<.01	.250	RI	<.01	<.01	.887
				Alc subj1	0.01	0.05	.257
				Alc subj2	0.01	0.01	.261

Note: *p < .05, **p < .01, ***p < .001; GzLM1 = generalized linear model without the retrospective data (N = 196); GzLM2 = generalized linear model including the retrospective data (N = 132). The dependent variable is the frequency with which participants responded on the button press task. Alc obj = blood alcohol concentration in percentages as measured with the objective alcohol meter; Parents = extent to which the parents are religious/spiritual; RI = response inhibition score obtained with the Stroop Task; Alc subj1 = subjective alcohol units consumed (range = 0–20); Alc subj2 = subjective alcohol high (range = 0–74).

The model in which retrospective data was included (see Table 5) also explained statistically significantly more of the variance than an intercept only model, χ²(17) = 44.51, p < .001, Log-likelihood = −593.85. Both age and education were statistically significant predictors. Specifically, the effect of education remained the same. Furthermore, increases in age were associated with decreases in the frequency with which extraordinary experiences were reported. Thus, younger participants had somewhat more frequent experiences. Finally, the effect of spirituality disappeared in the second model, and neither objective nor subjective alcohol intoxication were associated with the frequency of extraordinary experiences.

Intensity of extraordinary experiences. Principal axis factoring analysis. To combine the data of the subjective intensity item and the mysticism scale items into one “intensity of extraordinary experiences” measure, we used principal axis factoring (PAF) analyses with oblique (Promax) rotation (Russel, 2002). The Kaiser-Meyer-Olkin (KMO) measure was adequate; KMO = .50 (Field, 2009). Bartlett’s test of sphericity, χ² = 144.66, p < .001, indicated that the correlations between the items were appropriate for doing PAF. An initial analysis was run in which eigenvalues were obtained for each of the components. Cattell’s scree test (Cattell, 1966), a parallel analysis (Horn, 1965), and a test to investigate whether the Eigenvalue was larger than the mean (Field, 2009). Therefore, one factor, explaining 86.7% of the variance, was retained in the final analysis. The overall internal consistency was theta = .87 (Armor, 1973). The regression weights were used as a combined measure of intensity of the experience.

Intensity of extraordinary experiences. General linear models. Visual inspection of the normal P-Plot of the standardized residuals and a scatterplot plotting the standardized residuals against the standardized predicted values indicated that the assumptions of normality and homoscedasticity were violated respectively, for both the intensity models with and without retrospective data. To account for these problems, two measures were taken. First, a log transformation (i.e., LG10) was applied to the regression weights of the PAF plus a constant number (i.e., +1; to address the issue of negative values), increasing the normality of the distribution of the residuals (DiStefano, Zhu, & Mindrila, 2009). Second, a robust regression bootstrapping analysis with 2000 resamples was conducted to include a bias-corrected confidence interval of the beta values (Efron & Tibshirani, 1993).

In Table 6, the outcomes of both HLRs predicting the intensity of the extraordinary experiences are presented (HLR1 = model without retrospective data, HLR2 = model including retrospective data). In the first step of the HLR, the demographical variables did not explain a statistically significant amount of the variance of the intensity of the experiences, F(3, 183) = 1.81, p = .148, R²  = .03. In the second step, the predictors of the model did explain a statistically significant amount of the variance, although the explained variance was small (Cohen, 1992), F(8, 178) = 2.40, p = .017, R²  = .10. Both age and spirituality contributed statistically significantly to the model. As age increased, the intensity of the mystical experiences decreased. Importantly, the more strongly that participants considered themselves to be spiritual, the more strongly they perceived the intensity of the extraordinary experiences. Contrasting with our predictions, objective alcohol intoxication was not related to the intensity of the extraordinary experiences.

Table 6. Hierarchical linear regression models for predicting the intensity of extraordinary experiences.

	b	SE B	β	p
HLR 1
Step 1
Constant	0.03	0.16		.863
	[−0.29/0.35]
Gender	0.05	0.07	.06	.448
	[−.08/.18]
Age	−0.01	<0.01	−.13	.075
	[−.02/<.01]
Education	−0.05	0.04	−.09	.212
	[−0.13/0.03]
Step 2
Constant	−0.07	0.17		.690
	[−0.40/0.26]
Gender	0.01	0.07	.01	.862
	[−0.12/0.15]
Age	−0.01	0.01	−.17	.021*
	[−0.02/0.00]
Education	−0.03	0.04	−.06	.419
	[−0.11/0.05]
Religiosity	<0.01	<0.01	.04	.630
	[<0.01/0.00]
Spirituality	0.01	<0.01	.27	.001**
	[<0.01/0.01]
Parents	<−0.01	<0.01	−.08	.340
	[<0.01/<0.01]
Alcohol	0.06	0.10	.05	.525.
	[−0.13/0.25]
RI	<0.01	<0.01	−.02	.772
	[<0.01/<0.01]
HLR 2
Step 1
Constant	0.14	0.21		.502
	[−0.25/0.54]
Gender	0.03	0.08	.03	.696
	[−0.02/0.00]
Age	−0.01	0.01	−.16	.074
	[−0.12/0.17]
Education	−0.07	0.05	−.12	.174
	[−0.15/0.03]
Step 2
Constant	−0.11	0.22		.639
	[−0.52/0.36]
Gender	<0.01	0.10	−.01	.961
	[−0.02/<0.01]
Age	−0.01	0.01	−.14	.101
	[−0.16/0.14]
Education	−0.05	0.05	−.10	.279
	[−0.14/0.03]
Religiosity	<0.01	<0.01	.10	.301
	[<0.01/0.01]
Spirituality	0.01	<0.01	.21	.032*
	[<0.01/0.01]
Parents	<0.01	<0.01	−.02	.845
	[<0.01/<0.01]
Alc obj	−0.01	0.16	−.07	.564
	[−0.39/0.17]
Alc subj1	0.01	0.01	.11	.269
	[−0.01/0.03]
Alc subj2	<0.01	<0.01	.16	.132
	[<0.01/0.01]
RI	<0.01	<0.01	−.05	.550
	[<0.01/<0.01]

Note: * p < .05, ** p < .01; 95% CI between brackets; HLR1 = hierarchical linear regression model without the retrospective data (N = 193); HLR2 = hierarchical linear regression model including the retrospective data (N = 132). The dependent variable is the result of the log transformation of the regression weights of the principal component factor analysis conducted on the intensity scale and the mystical scale items. Parents = extent to which the parents are religious/spiritual; Alc obj = blood alcohol concentration in percentages as measured with the objective alcohol meter; Alc subj1 = subjective alcohol units consumed (range = 0–20); Alc subj2 = subjective alcohol high (range = 0–74); RI = response inhibition.

In the first step of the HLR with the retrospective data (i.e., HLR2), the demographical variables did not explain a statistically significant amount of the variance of the intensity of the mystical experiences, F(3, 128) = 1.95, p = .125, R²  = .02. In the second step, adding the residual predictors of the model did not explain a statistically significant amount of the variance, although the effect was close to significance, F(10, 121) = 1.91, p = .051, R²  = .07. Again, spirituality was statistically significantly predictive of extraordinary experiences, while neither objective nor subjective alcohol intoxication was statistically significant.

Discussion

The aim of the study was to investigate whether alcohol increases susceptibility to the God Helmet suggestion, and if such effects could result from impaired executive processing. We observed that (1) the placebo brain stimulation elicited a wide range of extraordinary experiences, (2) the data did not provide support for the hypothesized relation between objective and subjective alcohol measures, executive control, and frequency and intensity of extraordinary experiences, and (3) successful induction of expectancy-driven mystical experiences was predicted by participants’ self-reported spirituality. These three observations need further discussion.

First, the dependent measures as well as the open responses describing the nature of the experiences strengthened the proposition of previous researchers that placebo brain stimulation is a powerful manipulation to study extraordinary experiences (Andersen et al., 2014; French et al., 2009; Granqvist et al., 2005; Granqvist & Larsson, 2006; Tinoca & Ortiz, 2014; van Elk, 2014). The reported experiences relate to what people have reported in placebo conditions of studies on hallucinogens (Barrett & Griffiths, 2017) and to Hardy’s (1981) seminal collection on spiritual experiences. The categorization scheme we developed bears resemblance to some items of Persinger’s Exit Questionnaire (Persinger et al., 2000) and can be used as a helpful tool for future research as it extends previous work by indicating precisely what type of experiences may be induced, using expectancy manipulations of mystical experiences in combination with sensory deprivation. Building on this idea, one of the co-authors (MvE) already showed that the helmet could be framed as a “sound-helmet,” which led participants of a psychic fair to more often experience sounds, or a “visual-helmet,” which more often resulted in experiencing visuals (Van Elk, in preparation). This also makes clear that the expectancy manipulation adds to mere “sensory deprivation” effects that have been frequently reported in past literature (e.g., Glicksohn, 1991; Hood & Morris, 1981; Rossi, Sturrock, & Solomon, 1963). That the suggestive context adds to sensory deprivation effects converges with another study of ours (Maij & van Elk, in preparation), in which we observed that participants had more extraordinary experiences in a condition where they were wearing the God Helmet than a condition in which the God Helmet was taken off, while they were sensory deprived in both conditions. Thus, we argue that the effects that we observed in our study cannot solely be explained by the fact that all participants were to some extent sensory deprived during the “stimulation” with the God Helmet.

Scholars of religion who understand mystical experiences as happening only on rare occasions and in a very few people may ask the important question: what kind of experiences do these self-reports in God Helmet studies actually refer to? Do they really resemble the vivid hallucinatory experiences reported by spiritual virtuosos like Teresa Avila (Starr, 2007) and Ignatius Loiyola (Gleason & Mottola, 1989)? Or are participants simply prone to report extraordinary experiences without experiencing anything (i.e., a strong demand effect) – a concern that has often been raised in response to mysticism scale surveys and other self-report studies on religious experiences (e.g., Allister Hardy’s [1981] seminal collection on spiritual experiences).

Positioned somewhere between these two poles, the God Helmet may provide a unique context in which the combination of verbal suggestion, trust in modern science and technology, and sensory deprivation facilitates “real” extraordinary experiences. Specifically, the level of detail conveyed in the subjective reports that we obtained in our study provides convincing evidence that people were not merely confabulating, but reporting memorized experiences as if being real (Johnson, Foley, Suengas, & Raye, 1988). As explained in the introduction, the placebo brain stimulation effects induced by the helmet may best be understood in light of the predictive processing framework (Andersen et al., 2014; Büchel et al., 2014; Schjoedt et al., 2013; van Elk & Aleman, 2017). Supporting this idea is the observation that several participants noticed that the God Helmet session was remarkably similar to previous drug experiences they had (e.g., verbatim report by participant g). We argue that the contextual setting and expectations triggered them to remember or even “relive” these experiences. Furthermore, in line with the idea that randomly fluctuating bodily sensations are interpreted in a mystical fashion is the observation that most participants reported weak bodily sensations (e.g., itches and tingling sensations, feelings of relaxation and stress). Some participants themselves occasionally related their sensations to rational causes (i.e., causes outside the God Helmet). For example, one participant noticed: “My heart rate increased, but it may have been caused by tension.” Thus, comparable bodily sensations were interpreted differently on the basis of participants’ prior models (e.g., spiritualistic vs skeptic models).

Secondly, we did not find that alcohol increased susceptibility to the God Helmet suggestion. Similarly, other researchers failed to observe an increase in suggestibility following alcohol intoxication (Dienes et al., 2009). This indicates that alcohol may not increase suggestibility among those participants who would naturally be less prone to have extraordinary experiences with the God Helmet (i.e., people who consider themselves non-spiritual or even atheist). On the other hand, suggestibility has been successfully manipulated with other substances such as LSD, mescaline and nitrous oxide (e.g., Carhart-Harris et al., 2015; Sjoberg & Hollister, 1965; Weitzenhoffer, 1980; Whalley & Brooks, 2009). These psychoactive substances have also been known to be used in the context of religious rituals (de Rios & Winkelman, 1989; Ellens, 2014; Fuller, 2000). An important difference, however, is that the effects of these substances on bottom-up sensory processing are much stronger. Additionally, psychedelics are said to be consciousness expanders, whereas alcohol may have a reverse effect (i.e., narrowing of consciousness; Earleywine, 2005). Thus, it could well be that alcohol may not have such a powerful effect on the “mystical faculties of human nature” as William James (1902/1985) and others (e.g., Smith, 1964) once thought.

However, we ought to be cautious in dismissing the role of alcohol in facilitating extraordinary experiences. This is the first study on which the effects of alcohol on extraordinary experiences have been investigated, and this single study is not a definite answer to the question of whether alcohol can increase people’s susceptibility to extraordinary experiences. Importantly, overall levels of alcohol intoxication were rather low. We frequently observed that participants deliberately did not drink (too much) alcohol, because they thought that this might be dangerous in combination with the God Helmet, or they were afraid it would cause them to be excluded. The observation that alcohol intake was generally low was confirmed by the average BAC score on the objective alcoholmeter (i.e., around .03) and the relatively fast response inhibition scores (i.e., the mean was lower than observed in Bauer & Cox, 1998, on which the paradigm was based). We hypothesized that the effects of alcohol on extraordinary experiences would be mediated by executive functioning process. As expected, we did observe a statistically significant relationship between alcohol and executive functioning, similar to other studies (Finn, Justus, Mazas, & Steinmetz, 1999; Parada et al., 2012). The observed correlation was small (i.e., r = .20), but the environment was noisy, response inhibition is likely to be influenced by many other factors than alcohol, and the general alcohol intoxication was relatively low.

Nevertheless, future researchers should note that strong alcohol intoxication in combination with sensory deprivation could be problematic. The few participants who were strongly intoxicated were more likely to experience dizziness, to fall asleep, or to vomit, as they had to sit still with their eyes closed. A more fruitful way of investigating the effects of alcohol on extraordinary experiences may perhaps be to use a more ritualistic tribe-like context. For example, one could use a campfire setting with a shaman who supposedly gives a hallucinogen but provides the participants with alcohol. This could provide a more direct and more ecologically valid way of investigating the potential role of ritualistic alcohol use. Another possibility that should be considered is that people might have actively tried to compensate for the extent to which they were intoxicated by increasing attentional focus during the study (a similar explanation was given in a study on the effects of cannabis; Hester, Nestor, & Garavan, 2009). This would also explain the relatively weak correlation between alcohol and response inhibition of the Stroop Task. Furthermore, based on the predictive coding framework and looking at the studies on the effects of alcohol, it becomes evident that alcohol may well affect different processes at the same time (Easdon, Izenberg, Armilio, Yu, & Alain, 2005; Marinkovic, Rickenbacher, Azma, & Artsy, 2012). That is, alcohol may increase susceptibility to suggestions of the context, but it may also reduce awareness of sensory input such as bodily sensations and external sounds. These different effects may differentially affect the sensitivity to self-induced mystical experiences, thereby potentially explaining the absence of an overall effect of alcohol ingestion.

In addition, there were several disadvantages of conducting the study at a festival, which may have prevented us from observing an effect of alcohol. First, we were given only limited time to test the subjects, while it has been shown that the number of perceived mystical experiences increases with time spent wearing the God Helmet (Andersen et al., 2014). Second, the testing conditions were not optimal, leading participants to become distracted by external events such as the moving floor of the stage or the bass sound of other stages that could occasionally be heard. Third, although we initially hoped to acquire a more representative participant pool at the festival site than we usually recruit at our university, it is likely that the topic of the study (i.e., technology capable of inducing extraordinary experiences) resulted in a self-selection bias of participants, such as WEIRD (Western Educated Industrialized Rich Democratic) subjects, with a high “sensation-seeking” personality trait. Having outlined these limitations, this makes it all the more remarkable that extraordinary experiences were so frequently reported, again confirming that placebo brain stimulation is a powerful suggestibility manipulation. Finally, considering that the study was conducted at a music festival, it is good to elaborate on the possibility that participants under-reported their drug use, although we do not think this was the case. First, we tried to guarantee the anonymity of the participants as much as possible. They wore a sticker with a participant number, which they had to fill in themselves on the computer survey. Furthermore, the medical setting of the experiment (see also the pictures in the supplementary material) made participants cautious in being open about their medical conditions and use of alcohol and drugs. One of the most frequent questions we heard was: “Is it possible to do this with alcohol?” Participants also inquired several times whether it was possible to participate under the influence of “drugs.” Thus, although we cannot exclude under-reporting of actual drug use, the circumstances and informal observations make this possibility not very likely. In response to suggestions of reviewers, we investigated whether a nominal variable indicative of drugs and alcohol use (i.e., participants could indicate whether they used only alcohol, only drugs, both, or neither) explained some of the variance of the frequency or intensity of extraordinary experiences, but this was not the case.

Our last observation may explain why some people did report intense experiences. Like previous research (Andersen et al., 2014; Granqvist & Larsson, 2006), we found that reported experiences were predicted by participants’ self-reported spirituality, not by religiosity. What characterizes people who report being spiritual? Previous research has shown that spirituality relates to a focus on individual experience instead of religious dogma or religious membership (Fuller, 2001; Koenig, 2008; Saucier & Skrzypińska, 2006), openness to experience and absorption (Maij & Van Elk, in preparation), paranormal beliefs (Saroglou & Muñoz-García, 2008), and cognitive biases such as making ontological confusions or increased mentalizing (Lindeman & Svedholm-Häkkinen, 2016; Lindeman, Svedholm-Häkkinen, & Lipsanen, 2015). For people who self-identify as spiritual, vivid concepts related to spirituality could be the most easily activated in the context of the suggestible setting. In terms of predictive processing, the expectancy manipulation proved especially effective for people whose worldview matched the prior expectations we manipulated (i.e., people scoring high on spirituality). In another study (Maij & van Elk, in preparation), we have used different questionnaires relating to spiritual beliefs to investigate more precisely what individual differences could predispose participants toward having extraordinary experiences. We observed that the personality trait “absorption,” in particular, i.e., the tendency of people to get immersed in everyday events (e.g., “The sound of a voice can be so fascinating to me that I can just go on listening to it”), strongly predicted whether people reported extraordinary experiences by using a God Helmet manipulation. In short, extraordinary experiences are most likely to occur in participants who have a spiritual worldview that matches the expectations provided by the manipulation, and who are prone to get absorbed in spontaneous thoughts, bodily sensations, or external stimuli, that become more salient because of the manipulation.

In conclusion, even with suboptimal testing conditions, a large variety of extraordinary experiences were reported. Setting aside the limitations of the study, we did not find evidence that objective or subjective alcohol intoxication increased people’s susceptibility to an expectancy-driven manipulation, but future studies can settle this matter by using higher dosages of alcohol in a more ecologically valid context.

Acknowledgments

We are indebted to Bert Molenkamp for making the beautiful helmets, and we thank Kim Pieters, Kelly Vincent, and Tim Boxhoorn for their help with collecting the data. We thank Lowlands Festival, Rewan Jansen, and Noortje Jacobs from BKB for having made this study possible. Finally, we thank all participants for participating in the study.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was funded by a grant from the Netherlands Organization for Scientific Research (NWO: VENI Grant No. 016.135.135) and an AUFF grant from Aarhus University.

Notes

1 By belief in the supernatural (Latin: supranaturalis), we refer to all beliefs that are said to exist beyond (supra) nature (naturalis). They are cultural specific beliefs about phenomena that do not coincide with a naturalistic worldview and are therefore invisible and immeasurable.

2 http://lowlands.nl/programma/ll-science/

3 http://bigthink.com/videos/religion-and-god-helmets

4 http://www.millisecond.com/download/library/Stroop/