Magnetic Fields, Anomalous Experiences: A Sceptical Critique of the Current Evidence more

Magnetic fields, hallucinations and anomalous experiences: A sceptical critique of the current evidence Jason J Braithwaite presents a comprehensive critical assessment of an intriguing but controversial hypothesis OVER RECENT years, findings from a number of laboratory studies have suggested that anomalous hallucinatory haunt-type experiences can be artificially induced by applying temporally complex, weak-intensity magnetic fields to the outer cortex of the brain (see Persinger, 2001, for a review). The implication from these studies is that some spontaneous haunt-reports may be explained, at least in part, as magnetically induced hallucinations. However, although this view is very popular, it is often misunderstood by scientists, sceptics, paranormalists and the general public. Quite often in the popular literature and on the unregulated non-peer-reviewed internet this ‘neuromagnetic’ account is cast as one claiming that strong magnetic fields may exist in reputedly haunted locations as metaphorical ‘hot-spots’ and as such may be responsible for some anomalous perceptions, that any ‘blip’ on an EMF meter is meaningful, or worse still, that such fields may well be some physical correlate of the paranormality of a haunting. In addition, it appears to be the case that the idea is being accepted somewhat uncritically by some researchers as its apparent basis in physics and biophysics can be quite seductive at first glance. As a consequence of these observations, it appears to be a good time to take a closer and more evidence-based look at an argument that while tantalising, may well be, at the very least, insufficient as it currently stands. The present paper provides a comprehensive examination of the evidence for and against the neuromagnetic account. The nature of the argument will be characterised as it has been previously posed in academic publications which provides a refreshing tonic to the often intellectually bastardised ideas permeating the unregulated internet. In addition, a discussion of recent failures to replicate the effect of weak magnetic fields on human experience is also provided. It is argued that future research should concentrate on independent double-blind laboratory-based replications and on producing more explicit biophysical mechanisms for an interaction between weak temporally complex magnetic fields and the human brain. It is concluded that although the neuromagnetic account has support from some laboratory studies, it is nevertheless important to acknowledge that it is neither uncontroversial nor comprehensive in its current form. Magnetically stimulating the human brain It is important to point out that magnetic stimulation of the human brain is, in and of itself, not controversial. For example, Trans-cranial Magnetic Stimulation (TMS: see Walsh & Pascual-Leone, 2002, 2003) employs highintensity magnetic pulses of simple temporal structure to alter brain function. At the neuronal level the biophysics of TMS is relatively well known and widely accepted – revolving around the principles of electromagnetic induction (see Lomber & Galuske, 2002; Walsh & Pascual-Leone, 2003; for detailed reviews). Put simply, these principles state that for the stimulatory magnetic field to impact on neural systems, they must be capable of inducing a current higher than that available from the inherent noise present in the system at any given time. The success of inducing such currents in the brain is linked to the rate of change in, and the overall intensity of, the stimulatory magnetic field. Therefore, in order to achieve almost instantaneous effects in the brain, the amplitudes used in TMS are very high and are usually around the 1-Tesla range (often 10% - 30% less than the maximum of the stimulatory coil). The pulses themselves have a fast rise time of around 200 s (microseconds), can provide a pulse for around one millisecond (ms) temporal duration with an approximate one cm spatial resolution at the surface of the cortex. In cognitive psychology TMS typically provides a highly useful method of producing ‘virtual lesions’ (temporary disturbances) at precise points in time, in relatively discrete brain regions in the normal brain. This can help inform functional models and theories for how, where and when specific neurocognitive functions are being carried out. Therefore, it is important to be clear that uncontroversial methods of non-invasive magnetic stimulation of the human brain do exist and are widely used in contemporary behavioural neuroscience. However, it is also important to be clear that TMS is totally distinct from the methods employed in studies claiming to induce anomalous experiences in human observers and the two methods should not be confused. In contrast to TMS, Michael Persinger and colleagues have developed what they call the Trans-Cerebral Stimulation (TCS) method to induce hallucinations in normal participants. TCS employs very weak intensity, temporally complex magnetic fields to induce shifts in neural activity in the brain (Persinger, 2001). The fields employed in TCS are weak, generally in the nanoTesla (nT) and microTesla ( T) range and amplitudes in the 1000nT to 10,000nT (1µT - 10µT) range are typical across the majority of published studies (see Persinger, 2001). Here, magnetic field complexity rather than actual excessive field magnitude is argued to be the crucial factor for eliciting responses in neuronal systems via this method (Persinger, & Koren, 2001a; Persinger, & Richards, 1994; Persinger, Richards, & Koren, 1997; Persinger, Richards, & Koren, 2000; Ruttan, Persinger, & Koren, 1990). Importantly, unlike TMS, this method of stimulation does not appear to induce immediate changes at the neuronal level. Participants generally undergo 20 - 40mins of exposure before the effects on experience are reported. In addition, the spatial resolution of TCS is not specific, as these fields are applied in a general way to whole regions (e.g., lobes) of the brain at a time. Also it is typical with the TCS procedure to reduce sensory input (blindfolds, earmuffs, etc.) during experimental stimulation. On the whole, the effects appear to be general, nebulous and often non-specific. It is clear from the description above that the methods of TMS and TCS stimulation are quite distinct. In terms of TCS, it is difficult to see how the same biophysical method of magnetic induction could occur at such low amplitudes. The traditional view is that neurons are somewhat leaky capacitors and require sudden and intense changes to overcome this otherwise the energy trying to induce depolarisation (firing) in the neuron dissipates before depolarisation is complete (due to leakage). If the effects of TCS are genuine, then they imply a different form of biophysical coupling between brain and stimulatory magnetic field1. The fact that the specific biophysics underlying non-induction based magnetic stimulation procedures are somewhat obscure (after 20 years of research) is not a trivial observation and has led some to debate the biophysical plausibility of mid-intensity (60,000nT – 400,000nT / 60 T – 400 T) 38 www.skeptic.org.uk and weaker intensity magnetic fields impacting on neural processing (see Adair, 1991; 1992; 1998; Baureus-Koch, Sommarin, Persson, Salford, & Eberhardt, 2003; Del Giudice, Fleischmann, Preparata, & Talpo, 2002). A good deal of the controversy stems from thinking being influenced solely by the electromagnetic inductive model (as discussed earlier for TMS effects). This is hardly surprising. At the neuronal level, the energy associated with weak-intensity magnetic fields is several orders of magnitude lower than that which is necessary to overcome the existing energy parameters associated with ongoing electrochemical processes. According to this account, any energy weaker than that already inherent to, and available in, the system is unlikely to be detected by that system. These observations are fair and legitimate concerns and must be acknowledged in any sensible debate about these effects. However, these arguments are tied to the notion that electromagnetic induction is the only manner via which a biophysical interaction could occur. If one assumes that electromagnetic induction is the only mechanism for biophysical interactions to occur, then any situation that is not sufficient to produce such induction cannot induce a neuronal and experiential response. From this viewpoint it would seem that low-intensity magnetic fields have no consequences for neural processing at all (as direct and instantaneous electromagnetic induction is biophysically implausible at these low amplitudes). The current reality seems to be that the more we move away from the highamplitudes employed in TMS procedures, the further we move towards ambiguity in both the reality of an effect and the existence of a clear coupling mechanism between brain and magnetic field. Psychological and environmental factors in the haunt-type experience In terms of anomalous cognition, research has begun to identify and quantify the factors which contribute to some locations, and spaces within them, becoming associated with anomalous experience, hallucination and hauntreports. Such studies have suggested that a comprehensive physical examination of the location, a psychological and physiological examination of the observer, and the interaction between both location and observer is needed (Braithwaite, 2004; 2008; Braithwaite, Perez-Aquino & Townsend, 2005; Braithwaite & Townsend, 2005; 2008; French, Haque, Bunton-Stasyshyn, & Davis, 2009; Houran, 2000; Lange & Houran, 2001, 1997, 1998). In terms of psychological and physiological factors these studies have identified a legion of candidates including: (i) the existence of prior belief systems; (ii) suggestibility and the power of suggestion; (iii) contextual and situational factors … it is important to be clear that uncontroversial methods of non-invasive magnetic stimulation of the human brain do exist and are widely used in contemporary behavioural neuroscience The magnetic anomaly detection system (MADS) developed by Braithwaite and colleagues to investigate anomalous magnetic fields associated with reputedly haunted locations the Skeptic | Volume 22. Issue 4 / Volume 23. Issue 1 Photograph courtesy of Jason Braithwaite 39 available in the immediate situation; (iv) social contagion; (v) pre-existing cognitive biases impacting on the processing of information; (vi) neuronal vulnerability/instability (vii) cultural effects, and (viii) expectation, to name but a few (see Braithwaite, 2008; French, et al., 2009; Houran, 2000; Lange & Houran, 2001, Persinger, 2001; Wiseman, Watt, Greening, Stevens, & O’Keeffe, 2002; Wiseman, Watt, Stevens, Greening, & O’Keeffe, 2003: see also McCue, 2002; for a discussion). Field-based investigations of reputedly haunted locations have also identified a number of potential factors that appear to enjoy some statistical relationship with clusters of anomalous reports. These factors include; (i) low lighting levels, (ii) ambiguous sources of stimulation (iii) the presence of draughts (iv) room size (v) contextual and suggestive furnishings, and (vi) possible localised complex magnetic fields in certain cases (Braithwaite, The fact that the specific biophysics underlying non-induction based magnetic stimulation procedures are somewhat obscure (after 20 years of research) is not a trivial observation 2004, 2006, 2008; Braithwaite et al., 2005; Braithwaite & Townsend, 2005; 2008; Houran, 2000; Lange & Houran, 1997, 2001: Persinger & Koren, 2001a; 2001b; Persinger, Koren, & O’Connor, 2001; Persinger et al., 2000; Richards, Persinger, & Koren, 1993; Roll & Persinger, 2001; Wiseman et al., 2002, 2003). With respect to magnetic fields present “in the wild” so to speak, the suggestion is that specific spaces associated with haunt-reports may contain temporally complex though weak-intensity magnetic fields that may have the capacity to impact on and influence ongoing neural activity (see Persinger, 2001). A consequence of this biophysical interaction is that discrete changes in neurophysiology may vary in sympathy with the temporal complexity of the magnetic field — culminating in shifts in neural processing in vulnerable brains and thus facilitating altered states and hallucination. According to Persinger, these fields on their own have the capacity to induce anomalous experience in certain observers (who may also display an increased degree of neuronal vulnerability: see Persinger, 1983, 1984, 1987, 1988, 2001; Persinger & Koren, 2001a, 2001b). However, while it may be argued that magnetic fields have an important role to play in some cases, it has been suggested this is more likely, in the natural environment, if its impact is bolstered by other psychological, situational and contextual factors. In the absence of these other factors, the potential for magnetic fields to influence experience may be greatly reduced or it may even render such fields redundant. Indeed, recent research has suggested that the stimulatory potential of such magnetic fields might become apparent or increased if they exist within certain ‘spooky’ experiential contexts and in the co-presence of contextually loaded visual and semantic stimuli (e.g., gothic architecture and contexts provided by ancient castles, halls and old houses: Braithwaite, 2008; Braithwaite & Townsend, 2005; 2008; Houran, 2000; Lange & Houran, 2001, 1997, 1998). This could happen in a number of ways. One possibility is that the magnetic fields and Photograph courtesy of Jason Braithwaite Screen display from MADS 40 www.skeptic.org.uk experiential context work in concert to manipulate non-specific arousal and expectation in certain susceptible observers. Alternatively, the magnetic components may have generic effects on arousal which then may bias subsequent interpretations and impressions of ambiguous stimuli that occur within this context, towards a paranormal interpretation (Beyerstein, 1999; Houran, 2000; Lange & Houran, 1997, 2001). The source of the ambiguous stimuli could be in the immediate microenvironment (in the form of bangs, raps, draughts, fleeting visual effects, shadows, etc.) or indeed may be entirely internally driven (i.e. from within the brain itself due to increasing arousal). Irrespective of the source, once such ambiguous signals are provided in contextually loaded environments, a paranormal interpretation can now occur. These latter accounts suggest that the effects of magnetic fields may well be mediated by other contributory factors in the natural situation and in the observer. As such, anomalous magnetic fields, on their own, may not be sufficient to induce haunt-type perceptions in observers — but when and where they are present, experiences may be more striking and sustained (Braithwaite, 2008; Braithwaite & Townsend, 2005; 2008; Houran, 2000; Lange & Houran, 1997, 1999, 2001; Lange, Houran, Harte, & Havens, 1996). However, it is important to note that these more comprehensive suggestions are not what Persinger and colleagues have suggested and they represent a considerable extension of the laboratory findings. They are also, at the time of writing, highly speculative. Characterising the evidence for the neuromagnetic account The argument that weak-intensity (<10,000nT) magnetic fields could be implicated in some instances of haunt-type reports has been made based on three main strands of evidence; (i) correlational studies examining the relationship between changes in the general geomagnetic field and the incidence of anomalous reports, (ii) field-based studies of reputedly haunted locations and specific regions within them, and (iii) laboratory studies where complex magnetic fields have been applied to the brains of observers (see Persinger, 2001; Persinger & Koren, 2001a, for a review). Correlational studies have argued that anomalous reports are influenced by small changes (usually around 40nT — 60nT) in the Earth’s geomagnetic field (see Persinger, 2001; Persinger & Koren, 2001a for a review). These studies are the most questionable and the least convincing. For example, the magnetic field measurements that make up the background geomagnetic indices are typically based on averages taken from magnetic observatories that are often hundreds if not thousands of miles apart. It is difficult to see how very small changes in such general averages could have such specific and localised effects, for a minority of people, in very particular regions. The magnetic field strength and variability available from just walking the need for independent laboratories to carry-out appropriate replications under double-blind conditions has never been greater The MADS system has detected anomalous magnetic fields in the Tapestry Room in Muncaster Castle (above), especially around the bed area. There have been many reports of anomalous experiences from guests staying in the room. the Skeptic | Volume 22. Issue 4 / Volume 23. Issue 1 41 Photograph courtesy of Jason Braithwaite through the common home or travelling to work will be far greater than that available from geomagnetic sources. So the problem becomes one of how such small and general background transients could exert an influence in the presence of more localised, specific and far stronger sources (see also Braithwaite, 2008; Rutkowski, 1984, for other criticisms). In addition, the degree of change that occurs in the geomagnetic field is not only small, but is also very, very slow (with transients and changes often taking hours to manifest). As discussed below, this stands in contrast to the laboratory evidence which suggests fast changing temporally complex fields are crucial for inducing neurophysiological changes. Furthermore, although the geomagnetic indices from various observatories are well recorded, the spontaneous cases of paranormal events and experiences are not. Therefore, we do not have a comparable level of reliability in the precision of both these measures. Finally, the vast majority of reputed spontaneous paranormal phenomena, when carefully investigated, are shown to have relatively mundane causes. As a consequence of these observations the existence of significant correlations appears to be little more than a meaningless statistical artefact – and can be legitimately ignored. Field studies have tried to quantify the magnetic fields in reputedly haunted locations and compare them to appropriate baselines (see Braithwaite, 2004, 2006; Braithwaite et al., 2005; Braithwaite & Townsend, 2005, 2008; Wiseman et al., 2002, 2003 for example). The logic here is that if magnetic anomalies are implicated in a particular case of a haunting, then such anomalies should be measurable in the specific regions associated with hauntreports and be absent in the baseline regions which are not associated with such reports. More recently, the technology and methods for investigating the spatio-temporal structure of anomalous magnetic fields (and their stimulatory potential) has improved and is proving to be very revealing in one reputed field study (Braithwaite, 2004, 2006, 2008; Braithwaite et al., 2005; Braithwaite & Townsend, 2005, 2008). However, although methodologically superior to correlational studies, it is important to note that none of these field studies can support a causal role for such fields in anomalous reports. These investigations may show the copresence of temporally complex fields and clusters of anomalous experiences – but the documented instances where this has occurred are few and some may well be little more than a coincidence (as suggested by Braithwaite, 2008). The only way to provide evidence for a causal account would be to directly manipulate the magnetic fields, apply them to the brains of observers, and reliably measure behavioural and neurophysiological responses to these fields (relative to appropriate baseline conditions). In addition, some of these field studies are not beyond question themselves. For example, in the Wiseman et al. (2003) study of Hampton Court Palace, the variability in magnetic fields between the reputedly haunted locations and the baseline locations was statistically significant. However, in real terms the difference in this variability was only a standard deviation of around 11nT between areas (Stevens, personal communication). This is hardly likely to be important in terms of the magnetic field account, at least in terms of the amplitudes and variations employed in laboratory studies. Furthermore, no time-based information about the nature of the magnetic waveforms or their heterogeneity over time was provided and no frequency components were identified (time-based variability is crucial to the neuromagnetic account). One reason for the small difference in variability noted may well be that the magnetometer employed by the Wiseman team could only sample at a slow rate (once per second) and it may have been the case that such slow sampling was not fully capturing the true nature of the differences between the surveyed locations. Irrespective of this, such small differences in variability are not convincing field-based verifications of the account. The studies of Braithwaite and colleagues have employed high-speed dual sensor time-synchronised digital fluxgate magnetometery to examine both the spatial and temporal characteristics of magnetic anomalies in reputedly haunt- ed locations. These investigations have provided perhaps the most comprehensive attempt to explore Persinger’s account in the spontaneous natural setting. Here, both time-varying fields (DC – 125Hz) and distortions in the localised geomagnetic field can be quantified separately and simultaneously in threedimensions (x, y, z magnetic components). However, as noted by Braithwaite (2008), only two of around 50 investigated locations so far have produced magnetic fields that could be described as ‘temporally complex’. These instances could not only be termed rare, but also may in fact be coincidental. Although the advancements in precision and measurement are welcome, it remains to be seen whether the waveforms measured and detailed in these studies have any implications for human experience even in a loaded experiential context. In the absence of direct laboratory application of these fields to participants, the spectre that these anomalies may be little more than a false positive looms large. Braithwaite and French are currently exploring the possibility of reproducing the measured waveforms from the field studies in the laboratory setting. Findings from laboratory studies have suggested that anomalous perceptions and impressions can be artificially induced in the observer by applying temporally complex, weak-intensity magnetic fields to the brain (Cook & Persinger, 2001, 1997; Persinger, 1999, 2001, 2003; Persinger et al., 1993, 1997, 2000, 2001; Persinger, & Richards, 1994; see Persinger & Koren, 2001a). The likelihood of an interaction between the applied field and a neuronal response is increased if individuals have an increased degree of neuronal vulnerability (e.g., certain forms of epileptiform activity: Cook & Persinger, 2001; Makarec & Persinger, 1983, 1984, 1987, 1990; Persinger & Makarec, 1986, 1993; Persinger & Koren, 2001b). According to Persinger, anomalous perceptions can arise because these temporally complex magnetic fields are capable of inducing partial micro-seizures in temporal-lobe regions and the deep sub-cortical structures they house (i.e., the hippocampus/amygdala: see Persinger & Koren, 2001a). The essence of the account is that the induced micro-seizure can cascade through the neural landscape, with sufficient intensity, endowing internal thoughts, images, memories, feelings and emotions with enough activation that they become recruited into, and embellish, current ongoing perceptions. The outcome is a very real, yet very hallucinatory experience. However, as attractive as these ideas may be, there are some problems which are worth exploring. Firstly, although the effects of weak-amplitude fields have been documented for over 20 years, they are principally associated with one laboratory. Although these experiments appear to be well carried out and are methodologically sound, a principle of science is that effects should be replicable. Secondly, it does not appear that many (if indeed any) previous studies from the main laboratory have been carried out under truly double-blind conditions. To count as truly double blind in this context none of the experimenters running or even analysing the experiment (or the participants taking part), should be aware of which sessions contained the baseline sham fields and which sessions contained the crucial magnetic fields. If such procedures have been carried out, then they have not been clearly reported. Independent replications and failures to replicate: A closer look Only one independent study appears to have been carried out under what might be regarded as more stringent and appropriate double-blind conditions (Granqvist, Fredrikson, Unge, Hagenfeldt, Valind, Larhammar, & Larsson, 2005). Granqvist et al. did attempt to replicate the effects reported from Persinger’s laboratory and did indeed employ a double-blind procedure. This study failed to find an effect of weak magnetic fields impacting on experience and only reported a significant role for prior belief and suggestion. However, there were some important shortcomings with the Granqvist et al. (2005) study which should be noted. For instance, the study used a betweensubjects design where different participants were subjected to the sham baseline condition and the crucial magnetic field condition. It would have been 42 www.skeptic.org.uk preferable with these types of experiments to have people act as their own controls (i.e., a within-subjects design where participants take part in all experimental conditions). A between-subjects design would only have added more noise and more between-brain variability to the study. In this sense, the Granqvist et al. (2005) study is not a straight replication of the Persinger protocol and this is noteworthy. Secondly, Persinger has criticised the Granqvist et al. (2005) study by claiming that the fields they used may not have been appropriate for eliciting a neurological response (for example in not including appropriate temporal characteristics of the waveforms, Persinger & Koren, 2005; but see also Larsson, Fredrikson, Larhammar, & Granqvist, 2005, for a reply). Persinger and Koren (2005) have argued that the Granqvist et al. study ran the stimulatory procedures on a PC through Windows which would have distorted the temporal profiles of the fields applied. However, if the argument is that this procedure slightly distorted the crucial time-based nature of the applied fields to the point that they would not have biophysical effects, then the question becomes one of: at what point does temporal complexity become sufficient to induce biophysical effects? Or to put it another way, at what point is temporal complexity, temporally complex enough? This leads to a related issue with this particular line of argument. The implication from these magnetic studies is that as the amplitude levels employed in the laboratory studies are commonly available in the natural environment, the effects have a considerable amount of applicability in the real world (Persinger 2001; Persinger & Koren, 2001a). However, in their criticism of Granqvist et al., Persinger and Koren (2005) seem to be making the argument for a very special role for only certain forms of temporal patterns. The argument that a PC operating system can sufficiently distort the magnetic fields so as to render them completely neurophysiologically benign suggests that a high degree of temporal specificity may be necessary to elicit effects, assuming of course, that such effects do indeed exist. If complexity needs to be highly specific then presumably this would limit its applicability to haunt-reports in general, as such specific complexity is unlikely to be commonly available in the natural environment. There is certainly some friction between the notion that the magnetic fields hypothesis could be applicable to a host of haunt-type instances, as the amplitudes required are commonly available in the environment (increasing its ecological applicability), and the notion that very specific and exotic types of timebased complexity are necessary (reducing its ecological applicability) and any small deviations from some optimal waveforms render such fields impotent. Far from adding much needed clarity to the debate, the Granqvist et al. study, and the debate which followed, leaves one just as confused on the matter as before the study was carried out. This situation is far from ideal. As a consequence of this controversy, it would appear that the definitive independent double-blind replication study has yet to be carried out. Another recent study of note is that of French and colleagues who investigated the effects of many factors on anomalous perceptions in their ‘Project Haunt’ study (French, Haque, Bunton-Strasyshyn, & Davis, 2009). These researchers constructed a chamber in which participants could freely wander, but also, depending on the condition the participants had been assigned to, magnetic fields could be applied to an area within the space. French et al. also reported no statistically significant effects from the application of magnetic fields into the space relative to a condition where no magnetic fields were applied. However, similar to the study of Granqvist et al. (2005), predisposition to anomalous experience was reliably related to prior belief and suggestibility. Although there were no effects from the application of magnetic fields in this study, there were no controls over the levels of exposure people received either (as readily acknowledged by French et al.) – and as such, it is difficult to ascertain as to whether or for how long, participants were in the sections of the chamber where the coils and magnetic fields were located. Although both the studies of Granqvist and French may not be sufficient to directly falsify the neuromagnetic account as it has been cast, both studies do provide important constraints on the account and this should be welcomed. The Granquvist study, despite its methodological shortcomings, suggests at the very least, that (i) the effect is not easy to obtain, and (ii) the temporal complexity of TCS fields may need to be reasonably specific in order to elicit effects. The ‘Project Haunt’ study of French et al. (2009) suggests that the effects may be more slippery than first thought and do not seem to emerge by simply having such fields available in a space and people freely wandering through it. In addition, this study suggests that exposure duration may be more crucial in the real-world setting where there are more degrees of freedom and, as such, the competition between magnetic fields and other factors impacting on experience may be greater. As a consequence of this, future attempts at ‘real world’ replications of these effects should accommodate the need to address and control estimated exposure durations etc. The way forward By applying a certain degree of constructive doubt and scepticism to the literature surrounding the neuromagnetic account of haunt-type experiences, we can identify a clear way forward. Firstly, we need to ask ourselves to what extent is there really an effect to be explained at such weak intensities, and secondly, what plausible explanations are there for the underlying mechanisms? If the effect is shown not to stand up to repeated independent replication – then the need for an explanation becomes redundant. We do not need an explanation for an effect that is unlikely to exist! However, if the current evidence is to be accepted and future evidence supports it, then it appears there is an effect to be explained, albeit a subtle and somewhat nebulous one. At the very least the current evidence appears sufficient to warrant considerable further investigation. If the effects on behaviour and experience are reliable then they implicate some form of non-induction based coupling mechanism between a weak complex magnetic field and the human brain. This way forward can be thought of as improvements needed in two main ways (see also Braithwaite, 2006). These can be thought of as improvements in ‘prooforiented’ research and improvements in ‘process oriented’ research. To improve proof-oriented research there is a real need for independent laboratory replications, under appropriate double-blind conditions, to be carried out (following the helpful lead of Granqvist et al., 2005, and French et al., 2009). Granqvist et al. (2005) failed to replicate not just the effect, but also the method of TCS and so this must be taken into account when evaluating its usefulness as a direct falsification of the TCS method. Ideally, one would like to see a number of attempts at replication to aid the ever tricky navigation between generating false-positives and not having a method sensitive to reveal effects that are there – but have gone unnoticed. It is unlikely that a single independent failure at replication could offset the many tens of publications documenting effects (though a series of independent doubleblind studies would be highly evidential). In addition to this, improvements in process-oriented research need to come in the form of more explicit, testable biophysical mechanisms for the effects of weak-intensity fields to occur. Indeed, there may well be more than one mechanism capable of generating coupling effects between the magnetic environment and the brain. In addition, the delineation of the spatio-temporal characteristics required to endow a magnetic field with experience-inducing properties needs to be examined. Obviously, at such weak intensities, experience inducing effects may also be co-dependent on other factors such as; context, levels of arousal, cognitive biases, and neurophysiological susceptibility. Nonetheless, some principles of what is both necessary and sufficient across a variety of combinations would be a major advance in this field of research. Summary The idea that temporally complex, weak-intensity magnetic fields may be implicated in some instances of haunt-reports is a growing and influential the Skeptic | Volume 22. Issue 4 / Volume 23. Issue 1 43 one. One possibility is that the account could be a relatively common cause of haunt reports in the spontaneous natural setting. Although the suggestion of an effect between low-intensity magnetic fields and strange experience has some evidenced support, it is unlikely to be a common cause of haunt reports and is, almost certainly, not as common as other psychological factors such as expectation, prior-belief, suggestion and cognitive biases. The evidence for weak low-intensity temporally complex magnetic fields impacting on conscious experience is not incontrovertible. Correlational studies are perhaps the most controversial and least helpful to the debate – and can be legitimately ignored (see Rutkowski, 1984). Field-based investigations are providing a more detailed account of the spatio-temporal magnetic anomalies that might by associated with haunt reports, though they are insufficient on their own to support a causal account. Laboratory studies have the potential to provide the most useful, direct and reliable evidence. However, the need for independent laboratories to carry-out appropriate replications under double-blind conditions has never been greater. The evidence for high-intensity magnetic fields to exert an effect (TMS) is not controversial and the underlying biophysics is well understood. The lack of explicit accepted mechanisms for the effects of low-intensity fields does not make the account biologically implausible, although it does make it biologically obscure (at least based on the recent evidence). The findings are certainly mixed but on balance sufficient good quality prima facie evidence exists to warrant a dedicated approach to investigating the subtle and somewhat non-specific neuromagnetic account. However, the lack of a clear mechanism, or collection of them, should be openly acknowledged and provide the context for present and future theorising. Acknowledgements: I would like to thank Dr Wendy Cousins and John Jackson of UK-Skeptics for helpful comments on an earlier version of this paper. References Adair, R. K. (1991). Constraints on biological effects of weak extremely-lowfrequency electromagnetic fields. Physics Review, 43, 1039–1048. Adair, R. K. (1992). Criticism of Lednev’s mechanism for the influence of weak magnetic fields on biological systems. Bioelectromagnetics, 13, 231–235. Adair, R. K. (1998). A physical analysis of the ion parametric resonance model. Bioelectromagnetics, 19, 181–191. Baureus-Koch, C. L. M., Sommarin, M, Persson, B. R. R., Salford, L. 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Galuske (eds.), Virtual Lesions: Examining Cortical Function with Reversible Deactivation (pp. 249–284.). New York: Oxford University Press. Walsh, V., & Pascual-Leone, A. (2003). Transcranial Magnetic Stimulation: A neurochronometrics of mind. Cambridge: MIT Press. Wiseman, R., Watt, C., Greening, E., Stevens, P., & O’Keeffe, C. (2002). An investigation into the alleged haunting of Hampton Court Palace: Psychological variables and magnetic fields. Journal of Parapsychology, 66, 387–408. Wiseman, R., Watt, C., Stevens, P., Greening, E., & O’Keeffe, C. (2003). An investigation into alleged ‘hauntings’. British Journal of Psychology, 94, 195–211. 1 It is important to note here that there is a wide literature on the effects of ‘mid-intensity’ (60,000nT – 400,000nT, 60mT – 400mT) magnetic fields which is always ignored by parapsychologists. These studies are also controversial and, on the whole, seek to argue for a non-induction based coupling mechanism. These studies do show that even for magnetic fields which are simpler in structure, but many thousands of times stronger than those employed via TCS procedures, the effects are controversial, nebulous and a generally accepted biophysical mechanism remains elusive (see Braithwaite, 2008, for a discussion of this literature). Dr Jason J Braithwaite is a Lecturer in Cognitive Psychology and Brain Science at the Behavioural Brain Sciences Centre, University of Birmingham, UK. He has published widely in top international peer-reviewed journals in the fields of visual cognition, visual selective attention and its relationship to consciousness and awareness, hallucinations and anomalous cognition. the Skeptic | Volume 22. Issue 4 / Volume 23. Issue 1 45