A Reply To: "Can the 8 Coil Shakti alter subjective emotional experience?"

By Todd Murphy, inventor of the Shakti System, 2012

Summary: Using a test found to be ineffective in a previous study, Gendle & McGrath did an experiment with the 8 Coil Shakti's magnetic stimulation. They used a procedure that was unlikely to succeed, even with a reliable test (brain imaging, for example) to see it's effects. They made less than ideal choices about the time of day to do the stimulation, as well as the hardware they employed. Their study also shows some confusion about emotional reactions (emotional responses) and emotional states (mood).

The study shown above, by Mat Gendle and undergraduate Megan McGrath, duplicated a study done in the year 2006 by a group in Italy. The Italian researchers did
an experiment where 24 volunteers were shown a set of pictures that inspire different emotional reactions while they rated their emotional responses. Three measures were taken during the experiment: 1) skin conductance, 2) blood pressure and 3) heart rate.

At the same time, 12 of the subject's heads were exposed to an irregular magnetic field simulating the one encountered by the international space station while orbiting the Earth. The other 12 served as control subjects, receiving a "sham exposure". Skin conductance was significantly higher for those receiving the magnetic fields when these subjects were seeing "emotionally involving (positive and negative)" pictures, and lower while seeing neutral pictures. Those who received the magnetic stimulation showed a trend towards higher heart rates when viewing these same pictures, compared to those who did not. The field strengths of the Italian's apparatus varied, high peak to low peak, by about one Gauss.

The study found that the magnetic fields had no effect for either blood pressure or their emotional reactions to the pictures. Their subject's responses showed that the magnetic field didn't change the way they felt when they were seeing the the test pictures.

This article is about a similar study at Elon University that had the same outcome. One might wonder why someone would repeat an experiment that had already been found to have no result. The answer may be that it concerned a class of technology (which includes the
God Helmet) that has induced spiritual experiences, including visions of God in the laboratory - without drugs or hypnosis, and anything that relates to God commands attention.

The Gendle & McGrath Study qwerty

8 Coil Shakti feelgood session setup

The manufacturer's suggested coil placement.

  In June of 2009, an undergraduate student at Elon University ordered an 8 Coil Shakti magnetic stimulation system, Their intention was to observe its effects on emotion. During a phone conversation some time later, she was told that the best way to elicit significant emotional effects would be to select a subject group who feel at their worst in the morning, but don't have psychiatric disorders, and to apply the 'feelgood session' (which presents two magnetic signals, one after the other, with 4-second "latencies" - intervals with no signals - between them). In the mood enhancement feelgood session, the coils are placed over the frontal lobes . In their study, Gendle and McGrath applied the signals to the temporal lobes. These two signals are taken from the amygdala and the hippocampus, and there have been many reports of this session creating lasting mood changes. Here is only one of them - (From the yahoo group Mind-L, 03-20-2012):

"I now feel very balanced and calm and I can tell that a shift has occurred, as things that used to cause stress now seem to wash over me.
Overall, it has been a great experience and I'm very glad I'd made the move to use the device (The 8 Coil Shakti system). I will say though, that it wasn't without difficulty, since the process of making the shift does produce a certain level of upheaval. The first week started out almost euphoric, then the succeeding sessions seemed to buildup and cause some stress and it wasn't until the very last session that everything fell away and the stress was gone (it took about a day after that last session)."

To achieve such changes in emotional state, the 8 Coil Shakti's feelgood session should be repeated once a week for six weeks. It doesn't work equally well for everyone. It shouldn't be used if a person has a true psychiatric disorder, and it isn't expected to work if they feel at their worst in the evening. Like aspirin, which lowers body temperature in people with fevers, but not in people with normal temperatures, the feelgood session has little effect on people who already feel good. The design for the Feelgood session makes use of results obtained by Baker Price & Persinger in two
experiments with depression.

However, the process takes six weeks, and Gendle & McGrath decided to use a different session.

The placement Gendle & McGrath used.
Gendle & McGrath acknowledged that there are many positive reports from 8 Coil Shakti users online and even referred to "the device's success" as well as "notable anecdotal reports of its effects".

Gendle & McGrath used the 8 Coil Shakti system to apply magnetic fields with an embedded signal derived from the amygdala, over both temporal lobes of the brain. Then they showed the subjects almost the same pictures that the Italian researchers used. The difference is that the Gendle & McGrath took out the pictures that were explicitly sexual or violent, which would make the effect size smaller. Like the Italian study, the subject's responses didn't change. Of course, Gendle & McGrath knew about the Italian study - their report used it as a reference, and they used almost the same images. They knew that this very similar study had found that magnetic fields didn't change emotional responses to viewing emotional images when the Italians did it, but they went ahead and did the same experiment, using different magnetic fields.

Gendle & McGrath should have mentioned that the Italian study found no difference in emotional responses to the images with and without magnetic field stimulation, but their paper is silent on this point. The Italian study did find that heart rates and skin conductance changed when their subjects looked at the pictures under the influence of magnetic signals (based on the changing geomagnetic field patterns measured by the international space station), but Gendle & McGrath didn't measure either of these with their subjects.

The 8 Coil Shakti magnetic stimulation system is used for three things. 1) Altered state experiences, 2) meditation enhancement, and 3) mood enhancement. The Gendle & McGrath experiment was not designed to test for any of these.

The Gendle & McGrath experiment was to test their own hypothesis that exposure to the magnetic signal derived from the amygdala would "significantly alter emotional responses to these images".

They weren't testing the 8 Coil Shakti or its effectiveness; they were testing their own hypothesis, even though a very similar test had been done in the past, and also found no difference in the way the subjects responded to the same pictures.

They were studying changes in emotional responses to images using the Shakti system, but there's nothing in the Shakti documentation that suggests that it would affect the brief reactions people have to seeing a still image. Emotional responses to still images can be
very brief. Today, people are bombarded with powerful images from advertising, the news, movies, and the eroticism used to sell everything from cold drinks to motorcycles. Learning to disconnect from powerful images is an essential mental skill, and the more of them we see, the less time we spend on them. Emotional changes to pictures can be very brief; too short to be called changes in emotional state.

Gendle & McGrath show some confusion about their own results. In the title, they refer to "subjective emotional experience", a phrase that could refer to several different things. In the summary, they refer to testing for emotional responses, and in the text they go back and forth between discussing
states (mood) and responses. In fact, their procedure only examined emotional responses. They didn't take any measures of overall emotional state. For example, they didn't use questionnaires to see if their subjects were prone to depression, irritability, or any other emotional state.

Session Design

Gendle & McGrath used the amygdala signal over both temporal lobes, while claiming that they followed the manufacturer's instructions. However, both
the software and the website for the Shakti device have this to say:

"Using the amygdala signal over both sides equally is the safest way to begin using it, as this will activate it [the amygdala], but not change the left/right balance between hemispheres with respect to the amygdala's activation. The balance of left and right amygdala response will not be altered applying the signals to both sides. Rather, only the degree of activation of the amygdala for both sides (will change)."

In other words, the relative balance between the two amygdalas won't change, and neither would emotional responses from just one of them. The left and right amygdala would continue to exert the same controls over one another. This would reduce responses like elation or eroticism from the left amygdala, or startle responses from the right.

Shakti software also says this about the amygdala signal:

"A good starting point in using this signal over one side for those who choose to do so is the temporal lobes on the left side."

The 8 Coil Shakti software is clear that using the amygdala signal over both sides of the head will be safer, but will have fewer or weaker effects than using it over only one side. Specific effects have been found for one side that didn't appear when using it over both sides. One study suggests that subjects might have become resistant (hostile) to the stimulation when it was used over both sides, though that study used three sessions, and Gendle & McGrath used only one per subject. In spite of all this, Gendle & McGrath chose to apply the amygdala signal over both hemispheres, even as they reported that they followed the manufacturer's instructions for using the Shakti System. One should remember that this was an undergraduate research project, and that they were accountable to their university's review board and board of directors. Putting safety instead of "effect size" is to be expected in an undergraduate project.

The software also has a set of sessions designed for altered states, based on the design used in the
God Helmet experiments. When these sessions use the amygdala signal, they use it over one side, after another signal has been applied over only one or both sides. The God Helmet Experiments used the amygdala signal over both sides, but only after a different signal had been applied over just the right side. In the laboratory, the order in which the magnetic signals are applied (left/right or both) has proven to be important for most of the results. The feelgood session in the Shakti software - the one that the manufacturer recommended to Gendle & McGrath in a telephone consultation, - does use the amygdala signal, but it also uses another signal, and it doesn't apply them over the temporal lobes.

As they discussed their choice of signal, Gendle & McGrath mentioned
an experiment by Tsang (et al.), which used the amygdala signal, working with an earlier version of the Shakti system. However, in that experiment, the amygdala signal (called Burstx in the literature) was applied only to the left side of the head. Another signal, derived from the Hippocampus, was applied to the right side. In this case, again, the amygdala signal wasn't used over both sides.

"The circuit was designed so that the solenoids over the right hemisphere generated a theta-burst pattern (that)… when delivered as electrical current to hippocampal slices, produced robust long-term potentiation … Simultaneously, over the left hemisphere, the burst-firing pattern was generated to the solenoids. (Tsang, (et al.), 2004)".

The study Gendle and McGrath used as a reference for the amygdala signal only applied it over one side of the head. The other side of the head received a different signal. Both signals were described as "Burst patterns", but they were different burst patterns. The theta-burst pattern isn't the same as the laboratory "Burstx" or Shakti's amygdala signal.

As with the Italian study mentioned above, significant facts were left out of Gendle & McGrath's study. Their reference to the study by Tsang (et al.) was made only in passing, but it referred only to the amygdala signal, when in fact, another signal was also used. It might be an honest mistake, but it's still a misleading one.

Gendle & McGrath didn't use the tech support for the Shakti system. The only correspondence I received while the experiment was underway concerned requests for the password to unlock the software (which was lost a couple of times). When I waived the single-user license for their experiment, it was with the explicit understanding that they would contact me if they weren't getting any results. They did not.

Baker-Price & Persinger did two experiments with depression that used a burst-firing magnetic signal (amygdala signal) over both sides of the head. These experiments created emotional changes, and although they took five weeks to appear (with sessions once a week), the changes were still there when Baker-Price & Persinger followed up six weeks later. It took five weekly sessions for Baker-Price & Persinger to elicit the kind of changes that Gendle & McGrath were hoping to see in one day. Baker-Price & Persinger were working with depressed people, and Gendle & McGrath were working with a normal population.

Disturbed amygdalas respond to the signals more than healthy ones. When only one amygdala receives the signals, it will respond more than both of them would together (in a healthy person). When someone is depressed, the right amygdala makes more contributions to the person's mind than than usual. When the signals are applied to only one side of a healthy person's brain, that one amygdala also makes more contributions to the person's mind. This is why using the amygdala signal over only one side in a healthy person creates the same kinds responses that can happen when using it over both sides in a depressed person (of course, a healthy person would apply it only over the left side). It's also why using it over both sides with normal people has little, if any, effect, especially when it's used only once. There are a few circumstances where sessions over both sides are likely to be effective (such as in research with paranormal phenomena), but these didn't appear in Gendle & McGrath's experiment.

Suggestion and suggestibility.

In his experiments at Laurentian University, Dr. Persinger tells his experimental subjects that they are participating in a "relaxation experiment", implying that the God Helmet will make them relax. They go into the experimental session expecting to relax, which makes it more likely that they will do just that. This part of his procedure is somewhat deceptive, but it's not possible to put a complicated headset on the subject's head without giving them any explanation at all, and telling the subjects the real intention of the experiment would violate experimental protocols.

In another,
flawed, experiment that used the same kind of signals, subjects "were informed that the project was about the influence of complex, weak magnetic fields on experiences and feeling states." In that experiment, the subjects were openly informed of it's intention (while claiming that it was a double-blind procedure). It was not successful.

In the consent form for the Gendle & McGrath experiment, the subjects were "informed that any of the following might occur: (1) slight muscle twitching, (2) minor headache, (3) unusual skin sensations, (4) odd smells, (5) the subjective sensation of fear or a "sensed presence" (i.e., someone in the room), or (6) subtle alterations in perception and/or emotional states." They were told that these effects were unlikely, but they still offered a daunting set of warnings that could plant the suggestion that the procedure was dangerous. As successful experiments with this kind of technology included the suggestion that the subjects were going to relax, it seems probable that anything that it harder for the subjects to relax could interfere with its success. If they thought that the Shakti system posed any real risk, they would never have used it in an undergraduate project.

At one point in their paper, Gendle & McGrath wrote that "the potential effects that reading the consent form might have had on the results of the study also remain unclear." They speculated that it may have "served as a prime for such experiences". They also wrote that they thought this didn't matter because both the subjects and the controls both read the same forms. What seems more likely is that the chances for any such experiences to occur were
reduced in both groups, as both groups were given scary suggestions that would prevent them from relaxing (headache, fear, unusual skin sensations, etc.).

One strange thing about the Gendle & McGrath study is that there are two very different online versions of it's summary . The 'official' one was published by the Scientific journal Perceptual and Motor Skills. A different one, hosted by another university, speculates that the effects reported by the many Shakti users who have posted their results online are the result of placebo effect and personality factors. In point of fact, Gendle & McGrath didn't test for suggestibility, and didn't administer personality tests. Making two different versions of the same abstract available is a bit suspicious. Ordinarily, the final published version, and only the final version, is kept available. Other versions, being unpublished, will not have passed editorial review, and are considered spurious or untrustworthy.

Flexible Field Strengths.

Gendle & McGrath wrote that the field strength for their 8 Coil Shakti sessions measured up to one microtesla. This is the default field strength (which can be adjusted by changing the output [or volume] for the proprietary Shakti Signal Generator). The software contains the instruction that the field strength can be adjusted for different individuals, with women often responding to lower levels, and men responding to higher ones in many cases. However, using the same field strength for all men and all women can be a formula for failure. Ordinarily, Shakti users can use the tech support, which includes
a questionnaire asking about experiences that tend to indicate how excitable the temporal lobes and limbic systems are for each person (similar to the Roberts Inventory of Complex Partial Signs). When Shakti users fill out this questionnaire, they get a response that suggests specific session designs and offers advice about volume settings. This questionnaire wasn't used in this study, preventing the field strength from being adjusted for each subject. The software also instructs that the volume settings for the computer's sound card should be changed if someone has 'dud' sessions. Of course, Gendle & McGrath's subjects never got that chance, because each one only had one session, and none of them used the questionnaire.

Note: experiments at Laurentian University routinely use field strengths up to 5 microtesla, and the Shakti system can be obtained with a rebranded USB sound device that allows field strengths even higher than that. This was not available at the time the Gendle & McGrath obtained their Shakti system.

Gendle & McGrath wrote that they followed the manufacturer's instructions, but the instruction to make use of the tech support wasn't followed, leading them to work without the support of experienced people in the field.

Gendle & McGrath acknowledged "the possibility that
an inappropriate Shakti stimulus … was chosen in the attempt to enact alteration in subjective emotional responses to still pictures". Using the amygdala signal over both sides of the head is indeed an inappropriate choice, and the Shakti software's information about that signal made it clear that applying the signal that way is less likely to elicit any effects. If they had asked Shakti's tech support how to affect responses to still images, they would have been advised not to pursue that avenue of research, and if they insisted that that was the only test they wanted to do, they would have been advised to use the feelgood session, and to administer their test before and after the subjects completed a series of six weekly sessions. Even then, the results might not have been decisive, as no one who has used the feelgood session has ever reported its effects in terms of their response to viewing still images. Moreover, no tests using Gendle & McGrath's methods had ever been done in Persinger's lab, so there was nothing to compare them to, except the Italian study mentioned earlier.

Although their procedure (applying the signals equally to both side of the head instead of one side), would be expected to have only minimal effect on the subjects, it's worth looking at other features of Gendle & McGrath's procedure which may help explain their results.

Geomagnetic Factors

The amygdala signal is used (under its laboratory name; "Burstx") in the studies that elicited the sensed presence experience in Persinger's lab. However, this specific effect is more likely with
increased activity in the earth's magnetic field. The Gendle & McGrath paper noted that the earth's magnetic field was quiet during their experiments (Kp index {the geomagnetic levels} average for their sessions = 1.03, and never more than 0.76 higher or lower than that or Kp=1.03, SD=0.76). They were not testing for sensed presence experiences, so the absence of such effects isn't a stain on their results, but they did note that they didn't observe any "unusual perceptual experiences". The geomagnetic field levels offer only one reason for this. Another, as we've already noted, was that their Shakti Sessions treated both sides of the head the same. Still another is that their pre-experiment subtle suggestion that it might be dangerous would make it more difficult for the subjects to relax.


A final feature of their experiment is that they did their sessions during the day, while Persinger does his at night, when paranormal and spiritual experiences are more common, because melatonin levels are higher. Melatonin is important for both sleep and dreams, and if you aren't asleep when your melatonin is at it's peak, your chances for having a dream-like or deeply meaningful moment are much higher.

Gendle & McGrath wrote that claims of the sensed presence experience coming from the God Helmet would be bolstered by a demonstration that it can also affect "basic emotional states". Of course, their experiment didn't study emotional states - it studied emotional responses to pictures, a result that had already been found to be unaffected by magnetic field stimulation several years before, in a study they used to guide their choice of pictures.

The Gendle and McGrath study has a touch of confusion about the effects claimed for the Shakti System. They wrote about: "… claims that devices like the Shakti and Koren Helmet can be employed to induce "sensed presences" and other complex perceptual events…" The Shakti system's documentation doesn't claim that it can be used to induce sensed presences. There is no such claim anywhere on its website or in its software. There are a few pages that mention the sensed presence phenomenon, and some of the research investigating it, but there are no claims that The Shakti system can induce it.

Gendle & McGrath pointed out that they were investigating a weak field, and that they accepted that stronger fields are known to have significant effects. The Italian study we discussed at the beginning of this article used stronger fields and still had no effects on emotional responses, so their own reasoning (that weak fields might have smaller or fewer effects than stronger ones) should have pointed them
away from using responses to still pictures as a test of the system. But then, they weren't testing the device. They were testing their hypothesis that applying a magnetic signal, derived from an emotional structure, would change how people respond to emotionally-charged pictures.


The Shakti system receives its input from a computer sound device. The website says that most such devices are fine, but in laboratory work the best possible output device should be used. Gendle & McGrath used a Realtek HD sound device, an "onboard" sound source, even though the website says: "On-board sound devices are not as good as cards that you attach to your computer, and it's never a bad idea to install a better one. If you use your PC to listen to music, you'll notice a difference." There are many websites that review sound devices, and most of them agree that onboard sound devices (which are essentially sound chips attached to mother board) are
not as good as independent sound devices, such as PCI or USB devices. At the time Gendle & McGrath were doing their sessions, quality sound devices were routinely sent out to Shakti users. Most people take it for granted that 'laboratory standards' implies the highest possible quality, and if that's the case, Gendle & McGrath should have made a better choice. A failure to use the best sound device alone doesn't explain their results, but it would have been better to use a quality sound device.

Reply to: A Randomized, Placebo Controlled Study of the 8-Coil Shakti Device?