Testing an Effect That Runs Backward

Retrocausal, or "retro," PK experiments were designed by physicist Helmut Schmidt beginning in the 1970s specifically to isolate an unusually strong claim: that a person could mentally bias the outcome of a random process not while it was happening, but afterward, after the random sequence had already been generated by a machine and recorded on tape, and before any human being had looked at or otherwise interacted with the result.

In Schmidt's typical design, a machine would generate and record a long run of random binary outcomes with nobody present, and only later would a subject be asked to "influence," through concentrated intention, the proportion of one outcome versus the other in that already-fixed, sealed recording, with the results compared against untouched control sequences recorded the same way but never assigned to a subject. Schmidt reported statistically above-chance results favouring the subjects' stated intention even though the physical event had already occurred before the attempt was made. The paradigm deliberately sidesteps any explanation involving real-time influence on a live physical process, forcing the claim to rest entirely on an effect that would have to act backward across the interval between recording and attention, a stronger and stranger claim than ordinary micro-PK.