For a preliminary look at the possibility that reports of psychic phenomena can be influenced by emotional and psychological factors, I tracked down a paper co-authored by Richard Wiseman, Emma Greening, and Matthew Smith titled "Belief in the Paranormal and Suggestion in the Seance Room," published originally in the British Journal of Psychology, 94(3), 285-297. It is available online here (PDF).
Before going on, I should say that I have certain reservations about using this paper, because one of the authors, Richard Wiseman, has a dubious reputation in the field of parapsychology. Consider how he is characterized on the website Skeptical Investigations (which, despite its name, is actually an anti-skeptical site):
He has been at the centre of many controversies with researchers in parapsychology, and has often been accused of deliberately misrepresenting data.
In 1995, he replicated Rupert Sheldrake’s results with a dog that knows when its owner was coming home, and then claimed to have debunked the 'psychic pet' phenomenon....
He has been described by the President of the Parapsychology Association as motivated by "obvious self-interest", and by a desire "to support an a priori commitment to the notion that all positive psi results are spurious and all methods which seem to show the presence of psi are flawed".... In December 2000 he carried out what he described as the 'world’s biggest ESP experiment' which, like many of his activities, was widely publicised in the media. A skeptical observer of the experiment claimed that he had designed the experiment to fail and interfered with the procedure in such a way as to gain the non-significant result he expected.
In September 2004 he took part in a classic CSICOP debunking excercise, claiming that a young Russian girl who had seemingly psychic powers of diagnosis had failed a test he and his fellow skeptics designed. In fact the girl scored at a level well above chance. Prof Brian Josephson, FRS, a Nobel Laureate in physics, investigated Wiseman's claims about this test and found them to be seriously misleading....
By the autumn of 2004, after a series of other very questionable claims, widely publicized in the media, many of his peers in the parapsychology research community concluded that his behaviour was not consistent with commonly-accepted standards of scientific integrity, and he was voted off the main research forum in parapsychology by a large majority. In addition, for similar reasons, some members of the Society for Psychical Resaerch called for him to be expelled for the Society. He resigned. Despite his strong skeptical beliefs, in 2004 he applied for the newly-established chair of Parapsychology in Lund, Sweden, which was endowed to promote research in this field.
Obviously there are major controversies swirling around Wiseman. Nevertheless, I don't know of any other recent research that looks at the issue of suggestibility in the séance room. So with the caveat that Wiseman's conclusions may not be reliable, here's what he and his colleagues found.
The researchers put on a series of fake séances using an actor or, in a later series, Wiseman himself as the medium. The sessions were held in darkness, with various objects arranged on a table and glowing with luminous paint. During the course of the session, the medium would make suggestions to the sitters about the movement or lack of movement of these items. A hidden assistant would move some of the objects, using a long stick. The first series of experiments was videotaped using infrared photography.
The outcome of this initial series of tests was consistent with the idea that people in a dark séance room have a tendency to see things that didn't happen when these things are suggested to them by the medium. The most striking case involves the purported movement of a small table. Though the medium strongly suggested that the table was moving under the psychic influence of the group, the table actually remained stationary throughout the test. Nevertheless, 31% of participants later said that the table moved.
A second data point involves a small handbell, which also remained stationary throughout the test. In this case the medium told the group to focus their psychic powers on the handbell and make it move, but he did not suggest that their efforts had succeeded. In this case only 10% reported seeing the handbell move. This indicates that the medium's suggestion is an important factor in the way the session is remembered.
Moreover, people who expressed a prior belief in paranormal phenomena were significantly more likely to accept the medium's suggestions than those who expressed a prior disbelief.
The second series of tests yielded results that seem less conclusive. Still, there was a significant amount of misreporting. 11% said the stationary handbell moved. 10% said a stationary tambourine moved. 86% said that an actually moving slate remained stationary (the medium, Wiseman in this case, had strongly suggested that the slate wasn't responding to their psychic efforts, even though his assistant was in fact moving it). 9% said that a moving candlestick was actually stationary.
In addition to the above, many of the participants described feelings and sensations consistent with some kind of paranormal experience–the same kinds of feelings and sensations often reported by people who attended “genuine” séances.
In Experiment One, 20% of participants indicated that they had experienced these phenomena, with a significantly greater percentage of Believers (30%) than Disbelievers (8%) reporting such experiences (Chi square=6.36, df=4, p=.04). In Experiment Two, 21% of participants reported such experiences. In addition, the relationship between participants’ prior belief in the paranormal and the reporting of such experiences was in the same direction as Experiment One, and approached significance (Chi square=8.78, df=4, p=.07). The Questionnaire also asked participants to describe their experiences. Many people reported the type of quite dramatic phenomena often associated with ‘genuine’ seances, including being in an unusual psychological state (e.g., ‘Feeling of depersonification and elation when the objects moved’); changes in temperature (e.g., ‘Cold shivers running through my body when I concentrated hard on moving the objects’); an energetic presence (e.g., ‘A strong sense of energy flowing through the circle which increased’), and unusual smells (e.g., ‘A smell of hot plastic, combination of sweet and acrid smell’). Thus, the fake seances caused participants to report many of the experiences described by those attending ‘genuine’ seances, suggesting that such effects are the result of psychological processes (e.g., psychosomatic experiences brought about by participants’ heightened expectations or strong beliefs), rather than being caused by paranormal, psychic or mediumistic mechanisms.
Wiseman et al. sum up:
For over a century people have attended physical seances and reported witnessing seemingly inexplicable phenomena. Experiments conducted around the turn of the last century revealed that many of these accounts were unreliable. The experiments reported here have shown that modern day witnesses also produce inaccurate testimony of séance phenomena. In addition, these experiments represent the first attempt to systematically examine verbal suggestion within the context of the seance. They have demonstrated that such suggestions have the potential to cause sitters to incorrectly report that stationary objects were moving, and that moving objects were stationary. The studies have also produced strong evidence that within the context of a seance, Believers are significantly more susceptible to verbal suggestion than Disbelievers, but only when the suggestion is consistent with the existence of paranormal phenomena. Both experiments also revealed that during the fake seances many participants reported experiencing the type of unusual phenomena often associated with ‘genuine’ seances, including, for example, sudden changes in temperature, a sense of unusual energy and odd smells. Finally, results also showed that about a fifth of participants believed that the fake seance contained genuine paranormal phenomena, and that a significantly greater percentage of Believers than Disbelievers believed this to be the case.
Again, I don't want to put too much emphasis on this report because I do have doubts about Wiseman's credibility. It is worth mentioning, though, that the paper lists some prior research efforts that purportedly came to the same conclusions regarding inaccurate reporting of séance phenomena and (separately) the heightened suggestibility of believers in the paranormal. One of these papers dates back to 1887 and was co-authored by famed psychic researcher Richard Hodgson, best known for his work with Leonora Piper.
Hodgson and Davey (1887) held fake seances for unsuspecting sitters and asked them to write a description of the seance. They reported that many sitters omitted important events, recalled others in an incorrect order and often believed that they had witnessed genuine paranormal phenomena. In 1898, Lehmann (cited in Jahoda, 1969) conducted a similar experiment and again described how participants’ accounts of a fake séance were often wildly inaccurate. Besterman (1932) had sitters attend a mock seance and then answer questions relating to various phenomena that had occurred. Besterman reported that sitters had a tendency to underestimate the number of persons present in the seance room, failed to report major disturbances that took place (e.g., the experimenter leaving the seance room) and experienced the illusory movement of objects....
Haraldsson (1985) found a significant positive correlation between paranormal belief and the Gudjonsson Suggestibility Scale. Likewise, Dafinoiu (1995) reported a significant relationship between participants’ levels of paranormal belief and their scores on a suggestibility questionnaire, with people who believed in the paranormal exhibiting higher suggestibility scores than disbelievers....
Jones & Russell (1980) asked both Believers and Disbelievers to observe a staged demonstration of extra-sensory perception (ESP). In one condition the demonstration was successful (i.e., ESP appeared to occur) whilst in the other it was not. All participants were then asked to recall the demonstration. Believers who saw the unsuccessful demonstration distorted their memories of it and often stated that ESP had occurred. Disbelievers tended to correctly recall the demonstration, even if it appeared to support the existence of ESP.
If we can trust the Wiseman paper's summary of these various reports, it would seem likely that a fair amount of eyewitness testimony from séances in dark rooms is unreliable; that belief in the paranormal renders eyewitnesses more inclined to perceive these phenomena in response to the medium's suggestions; and that emotion and psychology play a large role in how séances are experienced and remembered.
In the Victorian era, when Spiritualism was all the rage, and may even have qualified as a kind of “mania,” these psychological and emotional factors could have been far more pronounced then they are in most people today. Perhaps this social atmosphere helps to explain the extraordinary prevalence of physical mediumistic phenomena in the late 19th and early 20th centuries, compared with their relative absence now.
Having said all this, I need to supply an important addendum. Some of the most convincing investigations of séances were not conducted in total darkness. For example, when Everard Feilding and his colleagues investigated Eusapia Palladino in Naples in 1908, they did so in conditions of dim but (reportedly) adequate light. They also took the precaution of examining the phenomena in detail whenever possible–for instance, crawling under a levitating table to ensure that all four legs were off the floor and that no part of Palladino's body was in contact with the table. These investigators were seasoned professionals who, among them, had exposed and debunked more than 100 physical mediums before encountering Palladino, whom they fully expected to debunk also. They hardly seem to have been carried away by irrational enthusiasm about mediumship, and given the lighting conditions and strenuous efforts to verify the phenomena, I don't think their results can be explained as hallucinations prompted by the power of suggestion (a possibility that the investigators themselves considered).
In short, the research done by Wiseman and his colleagues does seem relevant to a great deal of Victorian table-tipping and related physical mediumship when carried out in pitch darkness by excited amateurs or, in some cases, by overly credulous professionals. But I don't think it can disqualify the best and strongest cases from that era. It may, however, help to whittle down the number of good cases and to explain the extraordinary popularity of séances at that time. It may also explain why physical mediumship is so much rarer nowadays; perhaps people are simply not primed to accept it at face value as they once were.