Overview

The word psi comes from the Greek letter used as a neutral label in parapsychology. It does not assume any particular explanation. It simply names the class of effects that researchers are trying to study.

Psi splits into two broad types. The first is ESP, or extrasensory perception. This covers telepathy (mind-to-mind contact), clairvoyance (perceiving distant objects or events), and precognition (knowing something before it happens). The second is PK, or psychokinesis. This covers any case where a person seems to influence a physical system using only mental intention.

Parapsychologists use the word psi because it is theory-neutral. Saying “ESP” already implies a perceptual process. Saying “psi” leaves the mechanism open. That matters because no one yet knows what the mechanism is, or whether one exists at all.

Full historical context and scope will be added in a future curator pass.

Evidence and findings

Empirical findings from primary sources will appear here, with numbered citation anchors that resolve to the References section. The Sources toggle (top right) reveals or hides citation markers.

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Open questions

Several big questions remain unresolved in psi research.

First, what exactly counts as psi? The boundary between psi and ordinary psychological effects is not always clear. Researchers disagree on where to draw the line.

Second, if psi effects are real, what produces them? No physical theory currently predicts that minds should be able to send or receive information outside the normal senses. Some researchers look to quantum mechanics for clues. Others think entirely new frameworks will be needed.

Third, why are psi effects so hard to replicate on demand? Even researchers who believe the evidence is solid admit that results are inconsistent across labs and experimenters. Understanding why would be a major step forward.

Further open questions, flaws in how studies were run, and future research directions will be added in a future curator pass.

References