In a 2010 study by Wilson et al., researchers actually had participants perform over 15 sessions of séances. Their goal was to see if table lifting or floating would occur (Psychokinesis). Researchers were also interested in whether or not random number generators (RNG) would be affected by the séance sessions to produce non-random number series. Several meters and devices were also used during one session to examine changes in light and electromagnetic fields (EMF).
The researchers found that while RNG generators were not affected, but there were several instances of bizarre table behavior. In two instances the table appeared to move around on its own. In other sessions, the table tilted on two legs. In many of the sessions, rapping noises and knocks were heard. The researchers make no definitive claims that these events were faked, but do not claim that the movement was factual Psychokinesis.
In the session where light and electromagnetic fields were measured, there was a noticeable drop in infrared light (which is invisible to the human eye). Visual light also dropped to a noticeable level. Finally, equipment detected a noticeable increase of DC electromagnetic fields in the séance area, without any electronics or alternate sources that could account for the increase in field strength.
Fact or Fiction? You decide.
Wilson, M., Williams, B., Hart, T., & Roll, W. (2010). The Daniel experiment: Sitter group contributions with field RNG and MESA environmental recordings. Journal of Scientific Exploration, 24, 611-636.