### Random number generators in Psi experiments (07 Nov 2010)

*(Note: I'm not making any comment on the research in question, merely making a technical remark.)*

In Feeling the Future, the author, D. Bem, has an interesting problem (page 11 of the linked preprint). If an experiment shows that people can predict the output of a RNG, what does that tell us?

Well, if the RNG was a PRNG, seeded at the beginning of the experiment, then the subject could either be showing *precognition* (i.e. they can sense the result from the future) or *clairvoyance* (i.e. they can sense the state of the PRNG and thus know the next result). If you clock a true, hardware RNG before the trial then the same possibilities arise.

If you clock a true RNG *after* the trial however, then the possibilities are precognition and *psycokinesis* (i.e. the subject altered the state of the RNG, causing the result).

My observation was that you could XOR a PRNG and a RNG. (The latter being clocked after the trial.) In this case, prediction implies, at least, either *both* clairvoyance (for the PRNG) and psychokinesis (for the RNG), or precognition. That appears to be a useful trick.

However, this rather relies on the result that the sum of two RNGs is at least as random as the best of them. However, if we have a result which suggests precognition, then that doesn't hold! An evil RNG could, when summed with a true RNG, predict its future output and cancel it out, resulting in a less random result!