Debate concerning the

God Helmet text image.

A flawed attempt at replicating Dr. M.A. Persinger's God Helmet (also called the Koren Helmet) experiments yielded little or no results.

By Todd Murphy & Dr. Michael A. Persinger

Behavioral Neuroscience Program, Laurentian University, Sudbury, Ontario, Canada P3E 2C6,


Summary: This article summarizes Dr. M.A. Persinger's responses to a Swedish Research group's claim that the God Helmet's effects are due to suggestibility. Persinger maintains that his results are due to the specific patterns embedded in the magnetic signals he uses in his research. The debate between the two research groups has focused on the differing methodologies each group has employed. Several Internet pages have claimed that none of Persinger's results have been replicated, but this isn't true. A news story on the subject has even been published. An in-depth reply to critics who base their arguments on the Swedish group's flawed experiment is available online.

A picture of the hardware Persinger's group provided to Granqvist's lab.

The God Helmet experiments, in which a small percent of the subjects had visions of God, are famous because of the attention they have received from the media, including scores of journalists and television documentary teams.

Youtube videos showing the God Helmet in use.

Session with Michael Shermer, a well-known skeptic.

Another God Helmet Documentary

In the year 2000, a group of researchers led by Dr. Pehr Granqvist from Sweden's Uppsala university visited Dr. Persinger's Ontario Laboratory, asking to do a study that would measure the Koren Helmet's effects through PET scans. They were provided with hardware and procedures intended to create effects that PET scanning would detect, but the experiment they carried out actually had a different goal. They didn't want to monitor the neural effects. They wanted to induce the "sensed presence experience": the feeling that a non-physical being was in the room with them. This category of sensation includes deities, ghosts and angelic entities.
Granqvist omitted some essential preparatory work and procedures for his God Helmet experiment, and his conclusions overlook many of Persinger's procedures and discoveries. His group originally intended to work with PET readings, but appear to have changed their minds while preparing for their experiment. Instead, they chose to study the 'sensed presence' experience. Dr. Persinger's instructions for obtaining effects measurable through brain imaging were not the same as for inducing the 'sensed presence' experience. The brain responds enough to show changes in EEG traces some time before the subjects report subjective effects, including the 'sensed presence' experience.

The protocols for eliciting the "sensed presence" are different from the ones used to generate any response from the brain. The procedures Dr. Persinger gave them were designed to create any measurable change in the brain's state. Because shorter stimulations are ethically "less intrusive" than longer ones, Dr. Persinger gave them only the instructions to elicit a response that a PET scan could read. They had no experience with brain stimulation, so they received a simpler and less demanding procedure. It wasn't designed to stimulate the "sensed presence".

One of Granqvist's papers said that he wanted to do a pilot study before embarking on a PET study. It would have been interesting to see if changes in brain activity appeared on PET scans in the same amount of time they appeared on EEG readings (10 to 15 minutes), but Granqvist (et al.) never did the procedure they originally intended. They seem to have stopped their efforts after his failure to elicit the 'sensed presence', so he never did the studies for which Persinger provided instructions.

Granqvist's experiment was attempting to elicit the 'sensed presence' experience. However, in Persinger's words, his "methodology deviated significantly from the procedures known to evoke an experimental sensed presence" using the God Helmet (also known as the Koren Helmet).

NATURE reported that "Persinger, however, takes issue with the Swedish attempts to replicate his work, saying "They didn't replicate it, not even close,". Persinger's full response is available online.

Dr. Persinger publicly stated his view that the lack of communications between the two labs could have prevented the discrepancy between the results. He also made the email correspondence between himself and the Swedish research group available online.


The Helmet is connected to a PC computer, and controlled by a special software originally written for written for a 286 PC computer running DOS. The lab version must be run on a DOS operating system to function correctly. Unlike more recent versions, it could not be run under windows. Persinger's hardware connects to the PC through the LPT port (the printer port). Windows is always busy. It speeds up and slows down the output from Persinger's specialized signal generator as it handles system services. The changes in the throughput from the laboratory software is enough that Windows will "disconfigure (ruin) the temporal patterns of the applied magnetic fields.". The Granqvist paper mentioned that he ran the software in a DOS shell, under Windows 95. This adds a fractal-like distortion to the printer port's output, corrupting the signals. Persinger commented saying that "... the subjects in their experimental group never received an effective field configuration." "A double blind with no effective stimulus yields exactly what ...(they)... obtained: no effect."

In one of their papers on the subject, Granqvist (et al.) wrote:

"We used a DOS-based operating system (Windows 95) and the program ran stably in a DOS shell." The Swedish team assumed that running Persinger's hardware in a DOS shell would be the same as running it under DOS, as is done in Persinger's lab. The fact that the program was stable does not mean the the output from their computers was correct.

The program requires a native DOS environment, and a DOS shell under Windows isn't the same thing. The hardware connects to a computer via the printer (LPT) port, and so long as windows has control of that port, it will distort the output. The distortion from Windows doesn't affect the performance of a printer, but noise can be added to the output from other hardware when attached to the same port under windows. More recently, Persinger's laboratory has used PC audio systems to produce the signals for some experiments, an approach that circumvents this potential lab issue.

Only the original lab equipment needs to use DOS. The more recent version of Persinger's equipment runs under windows without any distortion.

Shows the difference between signals. Animation shows the spectral display from a 133mhz computer running windows 95 (as used by Granqvist (et al.) and the same from a computer in a true DOS environment.   "Notice the fuzziness around the main frequency peak components with the windows sample. This is what we referred to as the "Windows Warble". It seems that the heavy background load of Windows Operating System on the microprocessor causes a speed up and slow down operation of the waveform generator. This means that a chaotic or random timing component has been introduced. The CPU is multitasking and other programs have to wait while Windows deals with interrupts and other program requests. It would be analogous to listening to audio on a tape recorder that had poor speed regulation from a bad motor. One would then hear a 'warble' - constantly changing pitches. Stan Koren (personal communication)  


Granqvist's subjects were told that the experiment "was about the influence of complex, weak magnetic fields on experiences and feeling states". Persinger's subjects are told they are participating in a relaxation experiment. Blind experimental conditions require that the subjects not know anything about the purpose of the experiment. If anything, Persinger's procedures are more 'blind' than Granqvist's.

Granqvist (et al.) claimed that the reason why Persinger's results differed from their own was that Persinger's experiments weren't double-blind. In contrast to this claim, Persinger uses double-blind protocols. Here are a few references for papers where they were not only followed, but described in the papers. One example. | A second example. | And a third one. For comparison, Persinger uses a "Sham Field", meaning that the wires leading to the Helmet were disconnected for control subjects.

EEG machines have rows of pens.  The sight of one can suggest brain research-in-progress.

An Electroencephalograph

Granqvist wrote that his lab was "neutral in terms of affective induction", meaning that the setting gave the subject no clues about the procedure. But, he also wrote that the lab had two computers and an EEG. Persinger told his subjects they were participating in a relaxation experiment. Blind experimental conditions require that the subjects not know anything about the purpose of the experiment.

The intake information told Granqvist's subjects what the experiment was about (the influence of magnetic fields on feeling states), and seeing the EEG could have reinforced that information. His subjects were undergraduate theology and psychology students, two groups who are interested in mental health, and easily well-educated enough to recognize an EEG, with it's characteristic rows of pens.

In Persinger's experiments " ... the subjects were not aware of their experimental conditions and experimenters were not familiar with the hypotheses being tested or both were not aware of the experimental condition. Subjects were randomly or serially allocated to conditions. The person generating the hypothesis never had direct contact with the subjects".

Granqvist wrote that his lab was "neutral in terms of affective induction", meaning that the setting gave the subject no clues about the procedure. But, he also wrote that the lab had two computers and an EEG. Persinger told his subjects they were participating in a relaxation experiment. Blind experimental conditions require that the subjects not know anything about the purpose of the experiment.

The intake information told Granqvist's subjects what the experiment was about (the influence of magnetic fields on feeling states), and seeing the EEG could have reinforced that information. His subjects were undergraduate theology and psychology students, two groups who are interested in mental health, and easily well-educated enough to recognize an EEG, with it's characteristic rows of pens.

If you tell a research subject that they're helping to study the 'influence' of 'magnetic fields' on 'feeling states', and then walk them through a room with an EEG in it, you'll have presented the suggestion that they're going to experience neural stimulation. The subjects were given two cues about the nature of the experiment, one verbal (the experiment "was about the influence of complex, weak magnetic fields on experiences and feeling states"), and one visual (the EEG machine). His procedures (demanded by his university's ethics committee) planted the unmistakable suggestion that the subjects were going to receive brain stimulation. The popular image of brain stimulation, derived from movie sensationalism, could make them nervous and unable to relax. The Swedish group told the subjects to relax, but relaxation doesn't appear when ordered to do so.


Persinger described his procedure, which he used for experiments, television documentaries, and colleagues:

"The experiences were most easily evoked if a frequency-modulated pattern (tailored after a "chirp" sequence from standard signal generators) was applied over the right hemisphere for 20 minutes and then a bilateral burst-firing pattern (designed after the discharge of amygdalar neurons... ) was applied bilaterally over the temporal lobes for an additional 20 (or 30) minutes. These experiences occurred with equal vigor in dozens of reporters accompanying television film crews who have visited the laboratory during the last 10 years. The sensitivity of the functions of the right hemisphere to complex magnetic fields even within the picotesla range has been shown repeatedly by Sandyk".

In contrast, Granqvist applied the signals for only 15 minutes in each of the two parts of the session. The shorter sessions, especially for the first sequence make 'the sensed presence' and other similar experiences less likely. The difference of 5 minutes amounts to a 25% reduction in the length of the session, quite enough to eliminate reports from less-sensitive people, and influence the outcome of the experiment. The 15 minutes Persinger suggested were based on his understanding that the experiment was to measure the effects on PET scans. He uses longer exposures (25% to 100% longer) to induce the sensed presence, OBEs, etc. The sessions used in the God Helmet experiments have two sections and the first part sets the stage for the second. If the first stimulation isn't completed, it cuts the chances that the second portion will induce any significant effects.


Another point worth noting is that Persinger does the magnetic stimulation procedures with his subjects in an acoustic chamber equipped as a Faraday Cage, (an environment free of electromagnetic pollution), while Granqvist used an "isolation" chamber. A significant portion of the temporal lobe's activity is given over to monitoring ambient sound. The silence achieved in a completely silent acoustic chamber helps in eliciting the phenomena Persinger is known for, and it's replacement by a quiet isolation chamber deprives the sessions of true silence. This can reduce the number of experiences reported, as optimal conditions for the less-sensitive subjects are no longer present.
Complete silence isn't needed for all God Helmet effects, but it contributes to the 'sensed presence' experience.

  A comfortable chair is used.
Granqvist's isolation chamber was significantly smaller than Persinger's. Two cubic meters instead of the seven used in Persinger's lab. A bit cramped.
Sensing a presence is a lot less likely if the space isn't big enough for both the 'presence' and the subject.
The pictures shows Persinger's God Helmet and the experimental chamber (really a small room) with a happy member of his team.

It's also important to know that the chamber is a Faraday Cage as well. A Faraday Cage screens out EM pollution, and the many EM sources in the vicinity of Granqvist's lab (it includes an EEG machine, computers and monitors, probably a number of cell phones, possibly a PET scanner, and probably other sources) may have confounded the Swede's results. Persinger's procedures have always included a clean EM environment. Neither Granqvist's publications, nor his replies to Persinger, make any mention of his working EM environment.


Granqvist took the position that Persinger's results are due to suggestibility, even though he did not measure the trait directly in his subjects. However, Persinger found that his procedures can alter hypnotic suggestibility, and it's not possible to change suggestibility using the power of suggestion.

The effects the Swedes were hoping for could not have appeared with the distorted field patterns [or 'shapes'] they actually applied. Granqvist published that Persinger's effects were due to suggestibility. However, Persinger's research had long since reported that the God Helmet altered suggestibility (and imagination), so the possibility that the effects were due to suggestibility had been ruled out long before. Persinger's effects cannot be explained as suggestibility because suggestibility itself changes under the influence of different magnetic signals.

In addition to the studies that demonstrate paranormal effects, there are also studies published reporting significant after-effects. In two studies, Persinger and Baker-Price found lasting after-effects (a reduction in depression caused by closed head injuries). Follow-up for these studies lasted six weeks past the series of sessions. They also repeated the experiment, adding EEG monitoring to the procedure. Subjects reported a reduction in depression and phobias, a result that can't be explained through suggestion. If suggestion alone were enough to reduce depression, then hypnosis would be a well-established treatment.

The studies on depression are important with regard to suggestibility. They were done using the same hardware and one of the same signals as the better-known sessions seen on television. Based on the same principles as the experiments Granqvist tried to recreate, their success casts doubt on the Swedish team's conclusions.

Further, Persinger's results include cases where experiments found one signal was pleasant when applied over the right hemisphere, while over the left side a different signal was more pleasant.. This precludes suggestibility as an explanation. In order for a researcher to get such reports through suggestibility, they would have to plant very specific suggestions informing the subjects of the expected outcome. If one signal is pleasant when applied over the left hemisphere, and another is more pleasant over the right hemisphere, and the subjects are treated the same, then the in the effects obtained cannot be explained by suggestibility or placebo. (Persinger's blog on placebo effect.)

Scores of journalists, scientists, and television documentarists have had sessions with the God Helmet, and some of their experiences were very striking.

Susan Blackmore, scientist and author of over 20 books in consciousness research: "When I went to Persinger's lab and underwent his procedures, I had the most extraordinary experiences I've ever had," she says. "I'll be surprised if it turns out to be a placebo effect."

Dr. Michael Shermer, Founding Publisher of Skeptic magazine, Executive Director of the Skeptics Society, and columnist for Scientific American, reported that he experienced "Not only a 'sensed presence', but an out-of-body experience, as well."

Richard Dawkins, another noted skeptic, experienced a range of somatic sensations, but did not specifically have a 'sensed presence' experience. Apparently, Dawkins was drinking prior to his God Helmet Session.

Some scientists will dismiss these reports as 'anecdotal', but the chances that all of them are due to suggestion seem very remote. It's hard to imagine what kind of suggestion would trigger so many powerful experiences, and with such variety.


A recent study using equipment similar to the God Helmet found that subjects who were stimulated using simple magnetic fields talked about their experiences in different ways than controls. Their research report said that the effects were not due to suggestibility, and that they do indeed have an influence on the brain.

Their different equipment had measureable effects, though it was was not as effective as Dr. Persinger's.

Persinger's Procedure


Swedish Group's Procedure



Intended to elicit 'visitor experiences'.     provided to elicit any response that could appear on a PET scan. ......    Longer exposures are indicated for 'sensed presence' experiences to appear.    




Swedish Group



Applied each signal for 20 to 30 minutes.     Applied each signal for 15 minutes.     Persinger's published studies all use 20 to 30 minute exposure's for each portion of the session. Shorter sessions deliver less robust effects for many subjects.    




Swedish Group



Used a chamber with acoustic silence.     Used an "Isolation chamber" without acoustic silence, using earplugs instead.     True silence means that the temporal lobes have fewer tasks competing with the stimulation. Earplugs in one's ears offer a somatic distraction, and don't block all sounds.    




Swedish Group



Used an acoustic chamber with EM shielding (a Faraday Cage).     Used an isolation Chamber without EM shielding.     Some kinds of EM pollution can interfere with the God Helmet's effects.    




Swedish Group



Ran Signal generator, a DOS program, under a 100% DOS Operating System.     Ran Signal generator, a DOS program, under windows 95 in a DOS window.     Persinger has found that Windows distorts the signals so heavily that certain cognitive tasks become impossible.    




Swedish Group



Subjects are told they're participating in a "relaxation experiment" - the subjects didn't know the true purpose of the experiment.     Subjects "were informed that the project was about the influence of complex, weak magnetic fields on experiences and feeling states."     1) "Blind" experimental conditions require that the subjects do not know what kind of experiment they're participating in. The Swedish group's university required them to disclose the nature of the experiment to the subject, violating double-blind procedure.

2) By telling subjects that the experiment is to study how magnetic fields affect 'feeling states' Granqvist implied that they were going to receive brain stimulation, and this might have prevented them from relaxing, as they would have no chance to learn that the stimulation is safe. By telling the subjects that it's a relaxation experiment, Persinger helped them to expect relaxation, and relaxation is important for successful sessions.
In one report from Persinger's lab, the subject's EEG showed that they were not relaxing, even though they believed they were. Persinger told them to "Stop thinking so much".



Swedish Group



Regularly uses QEEG to monitor the subjects brain responses, in addition to noting their comments after the session.     Did not use any brain monitoring or imaging.     Without brain imaging or EEG monitoring, no quantitative measures of effects are possible. Persinger uses EEG regularly    




Swedish Group



Subjects did not see any EEG equipment, but did see the God Helmet, though they were told that it was a device to help with relaxation.     Said: "...the laboratory room and the isolation chamber were set up to be neutral in terms of affective induction." The stimulus equipment, an EEG device and two computers were present.     By letting the subjects see an EEG machine, the Swedish group gave a further impression that they subjects were going to receive brain stimulation.    


Persinger Argues


Granqvist Argues



The fields produced by the God Helmet interact with the magnetic fields within the brain, and the fields don't need to be strong enough to induce current. Current induction plays no role.     The fields produced by the God Helmet work through current induction, and the fields aren't strong enough to induce current in the brain.     When a magnetic field has a pulse, frequency or pattern, other magnetic fields nearby will pick up the information it carries. In this way, one magnetic field (like from the God Helmet) can input it's information to another (like those in the brain). This process happens without inducing electric current. It's a "field-to-field" mechanism.    
Although the brain's natural insulation can reduce the effects of EM emissions, the fields penetrate the skull because there is no such thing as a magnetic insulator.    


Persinger Argues


Granqvist Argues



Suggestibility can be increased with some God Helmet sessions.     God Helmet effects can be attributed to participant suggestibility     You cannot create a change in suggestibility through suggestion    



In contrast to the claim that Persinger's results have not been replicated, many of Persinger's effects have been seen in other laboratories. His finding of analgesic effects from his magnetic signals have been corroborated in a Toronto lab.

R. Sandyk has elicited several interesting effects with low intensity magnetic fields (including on Parkinson's disease and Multiple Sclerosis).

A research group in Switzerland has announced their success in eliciting spiritual effects from a device that duplicates Persinger's "Octopus". Persinger's theories regarding the effects of geomagnetism finds support in the work of several other researchers, including 1) Berk (et al.), 2) Kuleshova (et al.), 3) Burch (et al.), 4) Lashmanov & Koshelevskii.

Persinger's hypotheses on the connection between the brain's temporal lobes, religiosity and mysticism, are supported by the related work of 1) Trimble & Freeman, 2) Devinsky & Lai, 3) Asheim & Brodtkorb, 4) Kapogiannis (et al.), 5) Chan (et al.), and others.

A Brazilian research group recently found that there were significant differences in the verbal reports of subjects and controls, following stimulation with an apparatus not unlike the God Helmet. They published their results in 2014.

These are not exact replications, but they corroborate Persinger's findings that magnetic fields can influence brain activity. Further replication experiments may well be in order, but the state of today's economy means that there is less money available for such studies worldwide. Replication studies are not fulfilling for many researchers. The best they can do is confirm what others have discovered, and most prefer to pursue their own research agendas.


In conclusion, it looks like Persinger and the Swedish team obtained different results because of a series of differences in their procedures. The most critical of these may be that Swedish group's signals were distorted when the God Helmet's software was run under Windows (in a DOS shell), distorting the signals. These signals have very specific shapes, and anything that distorts them will prevent their effects from appearing (Persinger's metaphor compares the precision of a chemical shape to the needed accuracy of his magnetic signal's shape). It also looks like the Swedish team chose to work without contacting Persinger when their first sessions had no effect. It would have been better for all if the troubleshooting for the Swedes experiment had happened while the experiment was underway instead of after it's results were published. Persinger has done scores of experiments with the Koren Helmet. The Swedish group has done only one, and to conclude that the Swedes are right and Persinger is wrong is unwarranted.


Blogs by Dr. Michael A. Persinger on the God Helmet (and other subjects.

The God Helmet’s Weak Fields are Sufficient to Influence Brain Activity.  
We Do Not Allow Suggestion or Suggestibility to Influence our Lab Results.  
Our results can't be attributed to suggestion.  
God Helmet and many other of our results have been replicated.  
God Helmet Experiments use Blind Protocols and Placebo Controls.  
Replications of our work on Geomagnetism and Paranormal Phenomena.  
The Tectonic Strain Theory and French’s “Haunted Room” Experiment.  
Richard Dawkins – Alcohol and the God Helmet don't mix.  
My theories are not based on religiousness in epileptics.  
Religious belief is not an epileptic phenomenon.  


Also of interest:

Review of other research with Low-Intensity Magnetic fields.

Reply to critics of the Shakti Neural stimulation System.

Here is a Comment on a partial replication of M.A. Persinger's findings.

Brief summary of main issues with Granqvist (et al.) study.

News article on replication experiment.