A brief and incomplete history of telepathy science

Photo from Wikipedia. Click for sourceThe Fortean Times has a wonderful article that discusses the long and winding quest to find scientific evidence for telepathy, extra-sensory perception and other mysterious psychic powers.

The opening paragraph both made me laugh out loud and sets the scene for the rest of the article:

There are two truths universally acknowledged about extra-sensory perception (ESP). The first is that the anecdotal evidence is often fun and fascinating to read, whereas to peruse the experimental evidence is as boring as batshit, as our antipodean cousins say, and the investigative methods generally employed would for most of us banish insomnia for all time. We can’t avoid discussing these methods and their results in these entries, but we do promise to be brief and to strive personfully not to ruin your reading experience.

Link to Fortean Times on ‘Telepathy on Trial’.

Psychopath researcher threatens to sue critics

Photo by Flickr user Profound Whatever. Click for sourceRobert Hare is a psychologist who studies psychopaths and is best known for developing the ‘Hare Psychopathy Checklist’ or PCL-R, a standard diagnostic tool for assessing offenders. He is currently threatening to sue two psychologists who wrote an article critical of the theory underlying the checklist, as well as the academic journal, Psychologist Assessment, that accepted the piece for publication after it was peer-reviewed.

There’s an account of the affair over at the excellent forensic psychology blog, In the News, who note that the article was authored by respected researchers Jennifer Skeem and David Cooke and was titled “Is Criminal Behavior a Central Component of Psychopathy? Conceptual Directions for Resolving the Debate”. As a result of the legal threat the article has never come to light.

The letter from Hare’s lawyers apparently claimed that the he would:

“have no choice but to seek financial damages from your publication and from the authors of the article, as well as a public retraction of the article” if it was published. The letter claimed that Skeem and Cooke’s paper was “fraught with misrepresentations and other problems and a completely inaccurate summary of what amounts to [Hare’s] life’s work” and “deliberately fabricated or altered quotes of Dr. Hare, and substantially altered the sense of what Dr. Hare said in his previous publications.”

It’s probably worth noting that the PCL-R is big business. At current prices, each assessor who uses the checklist needs their own copy of the manual ($123) and the rating booklet ($68.50) and each individual assessment requires an interview guide at $5 each and a scoring form at about $3 each.

However, to use the assessment, each person needs to attend a training workshop at about $350 per person and workshops can easily involve 100 people at a time. Additionally, there is a follow-up correspondence course, price unspecified.

Because the assessments are used in the legal system, it is important that no-one (like an opposing lawyer in court) can find fault in the process and attending the ‘official’ training from the PCL-R company is considered the gold standard.

Recently, the affair has caught the attention of two lawyers and legal scholars who have just published their own analysis of the situation in the International Journal of Forensic Mental Health.

They express regret that Hare has chosen to use legal threats to counter his critics rather than to refute any points he felt were unfair in print himself, but also note that his strategy may actually undermine the usefulness of the PCL-R in court as opposing lawyers “may attempt to discredit that testimony by arguing that the literature relevant to evaluating the PCL-R has been tainted”.

Link to In the News on the case.

French government begins ‘neuropolicy’

Photo by Flickr user paul goyette. Click for sourceABC Radio National’s Life Matters covers the surprising news that France has created a brain and behavioural research unit specifically to form public policy.

The public policy in question is not just to do with the mind and brain and the director of the unit describes a ‘neuromarketing’ approach where the programme seems set to advise on how, for example, anti-smoking messages can be formulated.

As we’ve discussed several times, the ‘neuro’ of ‘neuromarketing’ is an interesting research focus but as an applied science it is completely premature and can currently tell us nothing about how best to appeal to the public that standard psychology can’t do already.

Rather worringly, unit director Olivier Oullier seems to think that ‘neuroscience’ and ‘neuroimaging’ allows access to unconscious and emotional responses that aren’t available to established behavioural research.

This is clearly crap and anyone who is aware of how neuroimaging studies are created knows that they rest on the quality of the psychological science.

It is also the case that not a single ‘neuromarketing’ study has shown a way to predict consumer responses, attitudes or preferences that improves on previously established cognitive science.

Psychology can be, and is, used to inform and evaluate public information campaigns and the effectiveness of public policy but at the current time brain scans are nothing but fairly lights.

UPDATE: Olivier Oullier got in touch to note that his interview was sparked by the release of a (very good) report [pdf] on ‘Improving public health prevention with behavioural, cognitive and neuroscience’. We’ve agreed to disagree on the value of neuroimaging in public policy right now, but he notes he’s actually a lot more measured in his analysis than you might of thought from my comments above.

Link to Life Matters on ‘Neuroscience and public policy’.

Mouse ache

Nature Neuroscience are about to publish a study that attempts to explain the biological basis of mouse acupuncture. If you’re checking in case you have accidentally slipped between universes, don’t worry, you haven’t. It’s just that this one has gone a bit strange.

The full paper is not out until later today and will eventually appear here, so I will reserve my full judgement (because, you never know, mouse acupuncture might be the next cure for cancer) but Not Exactly Rocket Science has read the paper and has a report of the bizarre study.

Apparently, it attempts to show a ‘biological basis’ for acupuncture by putting needles into mice at ‘traditional acupuncture points’ and then looks at the biochemical effects, particularly the release of a chemical called adenosine and riffs on the apparent ‘pain relieving effects’ from there.

The trouble is, no-one has reliably shown that acupuncture is more effective than placebo, and secondly, the Nature Neuroscience study itself apparently had no control condition, so you can’t even tell whether the effect in this study was specifically due to ‘acupuncture’ or not.

Just in case Ed at Not Exactly Rocket Science has got it completely wrong, I’ll have whatever he’s smoking, and if he hasn’t, I’ll have whatever they’re smoking in the Nature Neuroscience office.

Link to Not Exactly Rocket Science coverage.
Link where paper will eventually appear.

A scientific foil to your accidental brain injury

Inkling Magazine has a fantastic article detailing unusual objects which have accidentally ended up in the brain and have subsequently made the pages of medical journals as surprising case reports.

It covers everything from fairly lights to stiletto heels to human teeth and is cheekily titled ‘Not Right in the Head’. The article also mentions that the Neurophilosophy blog published a similar article two years ago, but rather surprisingly there was only one case that overlapped between the two.

The moral of the story is that if you can imagine it ending up in the brain, it probably has at some stage.

However, neither article mentions my all time favourite case, which involved a miniature fencing foil being lodged in the brain after being accidentally shoved through the nostrils (see a previous Mind Hacks post on things that have become stuck in the brain through the nose).

It was first reported in a 1968 article for the journal Neuropsychologia and just gives the following details:

N.A. (born July 9, 1938), a young American airman, was injured on December 15, 1960, while stationed at the Azores. The injury resulted from a mock duel with another serviceman, when a miniature fencing foil entered the patient’s right nostril and punctured the base of the brain, after taking an obliquely upward course, slightly to the left.

The case is not only notable for its strangeness, however, it is also one of the most important cases in the neuropsychology of memory.

NA suffered a dense amnesia, not unlike the famous Patient HM, without experiencing any other cognitive problems and while retaining his exceptional intelligence.

A major difference with HM was that HM had his hippocampi and surrounding tissue surgically removed on both sides while NA had a much smaller penetrating injury that largely affected his thalamus and a nearby pathway called the mammillothalamic tract – deep brain structures known to be widely connected to the brain’s outer cortical areas.

This was some of the first evidence that amnesia could be caused by damage to a ‘memory circuit’ and hence this type of conscious ‘declarative’ memory did not solely rely on the hippocampi, as was thought by some after the studies on HM.

We now know that damage to a circuit involving the hippocampus, fornix, mammillary bodies, the dorsalmedial nucleus of the thalamus and to a lesser extent, the septal nuclei, can cause strikingly similar amnesic problems and, hence, have been identified as key memory areas.

NA subsequently became one of the most studied patients in neuropsychology but because ‘NA’ is such a nondescript search term, in the age of the internet it has become easier to find studies on him by searching for “miniature fencing foil”.

A curious epitaph for such an important figure in our understanding of the brain.

Link to Inkling Magazine on unusual objects in the brain.
Link to Neurophilosophy on unusual penetrating brain injuries.

An explosion of visual hysteria

I’ve written an article for the magazine fotografya about how photography was initially used by doctors to document ‘hysteria’ in the 19th century but quickly became a vector through which the condition was spread.

The most influential photos came from the Salpêtrière Hospital in Paris, where, under the direction of neurologist Jean-Martin Charcot, hysteria was redefined to mean the appearance of apparently neurological symptoms, like paralysis or epileptic-like movements, without any clear damage to the nervous system.

Harnessed due to its presumed ability to objectively record the symptoms of patients, the camera became a vector for the condition, causing doctors to diagnose it in far greater numbers and for patients to express their distress through ‘hysterical’ symptoms in increasing numbers. We tend to think of media fashions as transient and frivolous but we forget that popular culture is as much an influence on illness and its treatment as science itself. For many, Charcot’s iconic pictures became the public expression of their private anguish and their documentary potential extended beyond the hospital walls to capture the broken spirit of the times.

These conditions are now known diagnosed as ‘conversion disorder‘ or considered to be ‘psychogenic’ in nature because psychological factors are thought to be behind the symptoms rather than what they appear to be – namely brain damage.

This means that the conditions are more likely to appear in people who already have experience of them, so early depictions of them were part of the process that led to an explosion in their appearance and diagnosis.

fotografya is a Turkish magazine and it has my original in English but I recommend checking out the Turkish translation as it is wonderfully illustrated by some of the striking photos of the time.

The article traces the history of ‘photographing madness’ from its clinical origins to its place in 19th century pop culture.

Link to article ‘Studio Charcot’ in English.
Link to Turkish translation with awesome illustrations.

2010-05-28 Spike activity

Quick links from the past week in mind and brain news:

Decorative illustrations of women scientists improves girls’ test scores on a chemistry test, according to research covered by Big Think.

The Philosopher’s Zone from ABC Radio National had a great discussion of Nietzsche and his idea of the ‘will to power’.

fMRI in 1000 words. An excellent piece from Neuroskeptic discusses the technology behind the popular neuroimaging technique, minus the analysis.

All in the Mind (the BBC version) has just started a new series. Still a little bit starched but (at bloody last) available as a podcast.

Spanish paper El País has a barnstorming piece on El mito de la adicción a Internet [The myth of internet addiction] which kindly quotes me.

The BPS Research Digest has a fascinating piece on how men with brown eyes perceived as more dominant but not because their eyes are brown.

A history of the ‘ultra pure heroin flooding the streets’ scare story. A brief but revealing article in Slate.

Neuron Culture has a wonderfully eclectic link shower featuring mechanical brides, lie detectors, enemies and risk taking.

The author of Drugstore Cowboy has just been arrested again, aged 73, for robbing drugstores, reports The New York Times.

Neurophilosophy covers a lovely study finding that watching forward or back computer motion directs idle thoughts to the future or past.

Does age mediate susceptibility to cognitive biases? asks Barking Up the Wrong Tree.

Wired discusses Aperger’s, institutionalisation and ex-hacker Adrian Lamo.

Remember the two teenagers who died after reportedly taking now-banned ‘legal high’ mephedrone? BBC News reports on toxicology tests that found no such drug in their bodies. Another triumph for media-driven drugs policies.

The Globe and Mail reports on research investigating the brain effects of poverty, although doesn’t delve too deep into which aspects of poverty may be having the effects.

The late Syd Barrett of psychedelic pioneers Pink Floyd warrants a short article in The American Journal of Psychiatry.

Science News reports on research finding that a version of gene 5-HTT makes children more vulnerable to the effect of bullying.

Leading psychiatrist Peter Tyrer slams the UK governments Dangerous and Severe Personality Disorder programme, reports The Guardian. There is some defence of the scheme in The Psychologist.

In The News has an excellent analysis of US laws aimed at marking out sex offenders and their unintended side-effects.

Cynthia Pomerleau, author of Why Women Smoke is interviewed on the excellent Addiction Inbox.

Wired Science reports that a shot of testosterone makes people more suspicious of each other.

Racial bias weakens our ability to feel someone else’s pain, according to research covered by Not Exactly Rocket Science.

BBC News reports on a study finding that prescribing heroin to long-term relapsing heroin addicts gives them a better chance of kicking the habit.

Airport psych security: snake oil on a plane?

Nature has an extensive article on the ‘deception detection training’ that’s been widely rolled out for airport security staff and anti-terrorism police despite that fact that is has barely been publicly tested.

As we reported in 2007, a great deal of this training seems to be based on psychologist Paul Ekman’s various methods for focusing on facial expressions as a way of improving the ability to detect lies.

However, there is no convincing evidence that has been published in peer-reviewed journals to suggest it can actually improve the ability to pick up deception.

The actual technique, at least as used by the United States, is called Screening Passengers by Observation Techniques or SPOT, and was apparently created ‘in consultation’ with Ekman.

The Nature piece also discusses another technology Future Attribute Screening Technology or FAST, which essentially just looks to see if someone is stressed, with the idea that it can pick out potential terrorists, again with no public data available on its effectiveness.

Now, it could be that there are a great deal of classified test results that show how accurate these systems are, but if not, I suspect that physiological threat detection has barely moved on for 50 years and entirely relies on whether someone ‘looks shifty’ and is demonstrably stressed, probably back up with a bit of statistical modelling to sort through passenger characteristics.

However, the Nature article does a fantastic job of questioning the basis of the current technologies and asking to what extent they are high-tech snake oil.

Link to Nature ‘Airport security: Intent to deceive?’.

Welcome to PsyOps Air

Wired’s Danger Room blog took a trip on Commando Solo, the US Air Force plane that’s been specially modified for the Psychological Operations or PsyOps division to create instant radio and television stations to broadcast persuasive messages to the people below.

As you might expect, the article doesn’t reveal a huge amount and there’s lots of close angle photos that look like the sort of thing a military aviation perv might take on the subway.

However, it does reveal a little about what it’s like to work in the mobile studio and it does mention the difficulty with measuring impact of their work – a constant point of contention with PsyOps work.

Measuring the effectiveness of a bomber or a strike fighter is fairly straightforward: The art of bomb damage assessment, measuring the size of a bomb crater or effective blast radius of airdropped weapons. What about when your weapon is a television or radio signal, and your goal is the somewhat more nebulous aim of “influencing” a target?

“The biggest challenge is measuring our effectiveness,” said Rice. “We don’t have a way to look at it — we don’t have BDA.

Link to Danger Room ‘Inside the Air Force‚Äôs Secret PsyOps Plane’.

Three Christs

In the 1950s, three delusional Messiahs were gathered to live together in the same mental hospital. This is one of the most remarkable experiments in the history of psychology and I’ve written about it in an article for Slate.

I’ve had this tale told to me many times, but in a hazy way almost like a myth. I’ve been asked it as a question (“what would happen if three delusional Christs met each other?”) other times it appears as a trite abbreviate anecdote (“did you hear about the three delusional Christs? One decided he was the Father, the other the Son and the other the Holy Ghost!”).

It was, however, a genuine experiment, carried out by psychologist Milton Rokeach in the 1950s, and written up in the sadly out-of-print book The Three Christs of Ypsilanti.

As Rokeach realised years later, the whole setup was entirely unethical and thankfully we have moved beyond manipulating patients’ lives for academic curiosity, but it remains a fascinating chapter in psychiatric history and I tried to capture the essence of it in the Slate piece.

These tales are surprising because delusions, in the medical sense, are not simply a case of being mistaken. They are considered to be pathological beliefs, reflecting a warped or broken understanding that is not, by definition, amenable to being reshaped by reality. One of most striking examples is the Cotard delusion, under which a patient believes she is dead; surely there can be no clearer demonstration that simple and constant contradiction offers no lasting remedy. Rokeach, aware of this, did not expect a miraculous cure. Instead, he was drawing a parallel between the baseless nature of delusion and the flimsy foundations we use to construct our own identities. If tomorrow everyone treats me as if I have an electronic device in my head, there are ways and means I could use to demonstrate they are wrong and establish the facts of the matter‚Äîa visit to the hospital perhaps. But what if everyone treats me as if my core self were fundamentally different than I believed it to be? Let’s say they thought I was an undercover agent‚Äîwhat could I show them to prove otherwise? From my perspective, the best evidence is the strength of my conviction. My belief is my identity.

Link to Slate article ‘Jesus, Jesus, Jesus’.

Singing in the rain

Photo by Flickr user Amelia-Jane. Click for sourceThere’s a common belief that the weather affects our mood, that we tend to become more depressed in the winter and that summer brings an emotional lift. This has been researched before in small studies that have found inconsistent results but a new study published in Psychiatry Research tested the idea on almost 14,500 people and found no link to weather, while the seasonal effects did not follow the common belief: depression was more common in summer and autumn.

The researchers, led by Dutch psychologist Marcus Huibers, tested both the effect of daily changes in weather and the influence of the season. They sent out thousands of invitations to to people in Holland to complete a standard depression diagnosis questionnaire on the internet, in waves of a few thousand every week, over 18 months.

This allowed the researchers to check the exact day’s weather against people’s mood states.

Neither that day’s temperature, the amount of sunshine or rainfall had any immediate effect on mood, and the seasonal changes were not what you’d expect from ‘common knowledge’: men had seasonal peaks of major depression and sad mood in the summer, while women had seasonal peaks in the autumn.

Although there are some people who do seem to have depression triggered when winter arrives (a condition diagnosed as ‘seasonal affective disorder’ or SAD) this link doesn’t seem to exist in the public as a whole.

I currently live in Medell√≠n, a city without seasons, to the point where it is nicknamed as ‘the city of eternal spring’. The locals says it used to be possible to tell the difference between the rainy seasons and dry seasons but over the last few years it’s simply been impossible to make any distinctions.

Interestingly, this has an effect on how we assess people for dementia. One of the ‘orientation’ questions for the widely used ‘Mini-mental state examination’ or MMSE evaluation is ‘what season is it?’.

As no-one knows what season it is, the assessment has to be scored out of 29 rather than 30, or it has to be replaced with something ad-hoc like ‘what part of the day is it?’.

However, it would be also interesting to find out whether depression varies here by time of year to understand whether this effect is really to do with season, or perhaps to do with the significance of the date.

For example, self-harm and suicide has been found to vary more by significant public holidays than by time of year.

Link to PubMed entry for depression, weather and season study.

The Inca DSM

A 1999 article about ‘Mental disorder among the Incas in ancient Peru’ in the History of Psychiatry journal has a listing of mental illness recognised by the Inca empire.

The name on the left is in Ancient Quechua, the language of the Incas, and the translation is on the right.

Chayapu oncuy – Frenzy, madness
Chayapuy – Frenzy, madness
Chayapuyniyoc – Frenetic
Chayapuyok urek – Lunatic
Cupaypa yaucusccan – Possessed by the devil
Haucha utek – Furious fool
Llakiy – Addiction, sadness, anxiety
Manchay Ilakllay – Fear
Manchay utek – Furious fool
Muzpaycachak – Fool madman
Poqques – Innocent fool who knows nothing
Pputirayay huaccanayay vnccoy – Melancholy
Putirayay – Melancholy
Putiy – Sadness
Soncconnak – Fool without common sense
Utek chanak – Madman
Utek chanaynin – Insanity
Utek cay – Insanity
Utek – Fool or madman without common sense

Interestingly, the translation is only approximate, not because the original terms were necessarily hard to understand but because we no longer know the meaning of the Spanish words which they were translated into.

Apparently, the the conquistadores had their own vocabulary for mental disorder which has now been lost to time.

However, it seems the Ancient Incas not only had a complex classification system but they also had a wide range of psychoactive plants which they used to try and treat mental problems.

Clearly there are some conditions mentioned that we wouldn’t recognise today but as soon as someone on the DSM committee gets hold of the article you can assured they’ll be proposed for the next edition. Probably alongside an academic article telling us that the condition is poorly recognised and woefully under-diagnosed.

I discovered the article via the excellent Spanish-language psychiatry blog Desde El Manicomio which also comes highly recommended.

Link to PubMed entry for Inca article.
Link to Desde El Manicomio.

From subliminal ads to Joanna the Mad

The Providentia psychology blog has been a consistently good read for as long as I can remember and if you’ve never checked it out a host of great articles have been posted online recently.

Just in May along there have been pieces on how a barking woman was declared unfit for trial, how the panic about ‘subliminal advertising’ started in the ’50s, why adolescents drink and whether the Spanish monarch Joanna the Mad was really mad.

It’s written by Toronto-based psychologist Romeo Vitelli and is well worth a visit.

Link to the Providentia blog.

Time compression and the causal connection

Photo by Flickr user evoo73. Click for sourceWhen we think two events are causally related we perceive the time between them to be shorter. Although this is news to me, it turns out the ‘time compression’ effect has been well researched.

Several of the studies have found that when we view two events but believe the first causes the second, time between them seems have gone quicker than when we perceive exactly the same scenario but think the two events are not connected.

This is a summary of the effect from a recent study that investigated whether your beliefs about how one thing is causing another affected the amount of time compression:

How much time might have elapsed between the launch of an economic program and the emergence of an economy from recession, between joining a dating service and finding someone you want to marry, or between giving your child a tough lecture about trying harder in school and seeing an effect on his or her performance? Recent research has shown that people subjectively bind such cause‚Äìeffect events in time and ‚Äúcompress‚Äù the time elapsed between them. Hence, for instance, if a parent believes that the tough lecture was the reason for an improvement in the child’s performance, the parent would estimate the interval [between the two] to be shorter. Several behavioral studies have established that people judge the time elapsed between pairs of historical events to be shorter when they perceive the events to be causally linked than when people do not perceive them to be so (Faro, Leclerc, & Hastie, 2005).

Similar effects occur on a shorter time scale. For example, in another study, when participants intentionally made a movement that appeared to cause a sound, they thought the events were closer together than when the two events occurred with no apparent causal connection

The new study helped explain the effect and showed that our beliefs about how we think one thing caused another are crucial to our experience of time.

It found that if people believe that cause and effect happened by a mechanical or physical process that was time limited the ‘time compression’ effect increased, whereas if it was an accumulative or ‘building up to a tipping point’ process, time didn’t seem so short.

Link to PubMed entry for time compression study.

Crack baby blues

I’ve just noticed a smattering of articles that have tackled the idea of the ‘crack baby’ which became popular during the worrying emergence of crack cocaine during the late 80s. It turns out that babies exposed to crack in the womb weren’t necessarily massively brain damaged tragedies as the stereotype had it, but the concept has remained with us.

This is despite the fact that we have solid research to show that while those exposed to cocaine in utero do show some differences from other kids, the effects are undesirable but actually relatively small.

This is from The New York Times last year:

Cocaine slows fetal growth, and exposed infants tend to be born smaller than unexposed ones, with smaller heads. But as these children grow, brain and body size catch up.

At a scientific conference in November, Dr. Lester presented an analysis of a pool of studies of 14 groups of cocaine-exposed children – 4,419 in all, ranging in age from 4 to 13. The analysis failed to show a statistically significant effect on I.Q. or language development. In the largest of the studies, I.Q. scores of exposed children averaged about 4 points lower at age 7 than those of unexposed children.

In tests that measure specific brain functions, there is evidence that cocaine-exposed children are more likely than others to have difficulty with tasks that require visual attention and “executive function”, the brain’s ability to set priorities and pay selective attention, enabling the child to focus on the task at hand.

Cocaine exposure may also increase the frequency of defiant behavior and poor conduct, according to Dr. Lester’s analysis. There is also some evidence that boys may be more vulnerable than girls to behavior problems.

But experts say these findings are quite subtle and hard to generalize. “Just because it is statistically significant doesn’t mean that it is a huge public health impact,” said Dr. Harolyn M. Belcher, a neurodevelopmental pediatrician who is director of research at the Kennedy Krieger Institute’s Family Center in Baltimore.

A piece from City Limits Monthly tracked how the myth arose. It’s probably the best account I’ve read of the cultural currents that promoted the concept to front page news and keep it afloat even today.

And just last month The Washington Post talked to some families of kids labelled as ‘crack babies’ now that they have grown up into adults finding that, well, many have done alright.

Link to NYT on ‘The Epidemic That Wasn’t’.
Link to great City Limits analysis (via @maiasz)
Link to Washington Post piece (via @sunshinyday)

Hallucinating the void

Rhode Island Medical News recently published an April fools article where the author joked about negative hallucinations, where someone didn’t see things that were really there, seemingly unaware that such hallucinations are in fact possible.

The article, which you can read online as a pdf, has various humorous references to jumping traffics lights or ignoring family members. But when I’m talking about the genuine version I don’t mean lapses of attention, blind spots, inattentional blindness or other momentary failure-to-notice effects. I’m talking about not seeing specific barn door obvious objects in your field of vision when you are concentrating on the area.

These are genuinely called negative hallucinations in the scientific literature although, as far as I know, they only occur in one specific context – after hypnosis.

In fact, the induction of a negative hallucination forms part of the Stanford Hypnotic Susceptibility Scale (Form C) although these sort of ‘anti-hallucinations’ are only experienced by the most hypnotisable of people – as are most ‘cognitive’ suggestions that effect the experience of your own mind (rather than changes in the sensation of control of movement, which most people can experience something of).

There is a small literature on ‘negative hallucinations’ with several studies examining changes in electrical activity from the brain (‘evoked potentials’) as the hallucination becomes active.

It’s still not clear how negative hallucinations work exactly. Almost all studies have found changes to attention, our ability to selectively process perceptual information, although the data is inconsistent largely owing to the small number of studies – a constant bugbear of hypnosis research.

Link to April fools article PubMed entry.
pdf of full-text
Link to Google Scholar search of negative hallucination studies.
Link to PubMed search of negative hallucination studies.