That is new information to me.
I'd be very interested to read the study if you can dig it up.
I found the book (Paranormality: Why we see what isn't there, by Professor Richard Wiseman) and there are several references in it. Here they are...
P. Granqvist, M. Fredrikson, P. Unge, A. Hagenfeldt, S. Valind, D. Larhammar and M. Larsson (2005). 'Sensed presence and mystical experiences are predicted by suggestibility, not by the application of transcranial weak complex magnetic fields'. Neuroscience Letters, 379, pages 1-6.
M. Larsson, D. Larhammar, M. Fredrikson and P. Granqvist (2005) 'Reply to M.A. Persinger and S.A. Koren's response to Granqvist et al. "Sensed presence and mystical experiences are predicted by suggestibility, not by the application of transcrancial weak complex magnetic fields"'. Neuroscience Letters, 380, pages 348-50.
Other tests of magnetic fields...
C.C. French, U. Haque, R. Bunton-Stasyshyn and R. Davis (2009). 'The "Haunt" Project: An attempt to build a "haunted" room by manipulating complex electromagnetic fields and infrasound'. Cortex. 45, pages 619-29.
J.J Braithwaite (2008) 'Putting weak magnetism in its place: A Critical examination of the weak-intensity magnetic field account for anomalous haunt-type experiences'. Journal for the Society of Psychological Research, 890, pages 34-50.
J.J. and M. Townsend (2005). 'Sleeping with the entity: A quantative magnetic investigation of an English castle's reputedly haunted bedroom'. European Journal of Parapsychology. 20.1, pages 65-78.
Apologies for the lack of italics but I can't do them on my Wii. Also I don't know how good these journals are but here you go anyway.