Retrocausal Psychokinesis

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.

Retro-PK inherited every methodological problem that dogs ordinary micro-PK research, small effect sizes requiring large trial pools and careful statistical handling to detect at all, plus an additional theoretical burden: any confirmed retrocausal effect would require revising basic assumptions in physics about the direction of causation, a bar considerably higher than an ordinary anomalous psychological finding. Schmidt's results were reported within parapsychology journals and were followed by a small number of further studies attempting similar designs, some by researchers openly skeptical of the paradigm who nonetheless reported comparable statistical anomalies, which proponents took as independent support.

Critics countered, as with other RNG-based psi research, that hardware and software artifacts in the random-generation and recording process, subtle non-randomness in the "random" source itself, selective analysis choices, and the general problem of pooling many small trials to manufacture apparent statistical significance, could account for the reported effects without invoking any real retrocausal influence. No retro-PK result has been replicated by a laboratory outside the parapsychological research community to a standard that community's own critics or mainstream physicists accept, and the paradigm remains a minority, contested line of inquiry closely tied conceptually to the equally unresolved dispute over precognition, most visibly reignited by Daryl Bem's 2011 experiments, which used a similar logic of effects apparently preceding their causes.