A Very Small Effect, Sought in Very Large Numbers

The laboratory's core experiment was undramatic by design. An operator sat in front of a machine producing a stream of random binary digits from electronic noise, stated in advance whether they intended to push the output high or low, and then tried. A run consisted of thousands of bits, a session of many runs, and the database of many thousands of sessions across nearly three decades. Nothing visible happened during any of it. The claim was that when everything was summed, the totals in the intended direction exceeded the totals in the baseline condition by an amount that was tiny in each run and, in aggregate, statistically significant. Robert Jahn characterised the magnitude as being on the order of one part in ten thousand.

The methodological bet behind this design is worth stating clearly, because it is the source of both the programme's appeal and its trouble: if a real effect is very small, the only way to see it is to collect enormous quantities of data, but enormous quantities of data are also the condition under which very small biases in equipment, in analysis and in stopping rules become visible as apparent effects. The laboratory also ran a second line of work on remote perception, closer to the SRI protocol than to the generators, which is less often discussed and was reported to smaller effect.