In 1999, researchers French and Williams conducted a study to investigate the power of crystals compared with a placebo. Eighty volunteers were asked to meditate with either a quartz crystal, or a placebo stone which was indistinguishable from quartz. Many of the participants reported feeling typical "crystal effects"; however, this was irrespective of whether the crystals were real or placebo. In 2001 Christopher French, head of the anomalistic psychology research unit at the University of London and colleagues from Goldsmiths College outlined their study of crystal healing at the British Psychological Society Centenary Annual Conference, concluding: "There is no evidence that crystal healing works over and above a placebo effect.”