I have an impression that most parapsychologists around the world--I don't know about those in the Soviet Union--have given up the notion that psi phenomena can be explained by any known force of nature. At any rate, the fashionable trend in the United States and England is to conjecture that somehow the phenomena can be identified with a yet-to- be-discovered force-field that would also account for those paradoxes of QM in which information seems to be transmitted either instantly or at a speed faster than light.
Many paradoxes in QM appear to require such a field, but none is more debated at the moment than the notorious EPR paradox. The letters refer to Einstein and two young colleagues, Boris Podolsky and Nathan Rosen. In 1935 the three published a paper in which they argued that QM was incomplete because it does not explain how two particles can remain "correlated" over vast distances without being causally connected.
The EPR paradox has numerous forms, but the easiest to explain is a version first proposed by physicist David Bohm. It involves a property of particles called "spin" because in some ways it resembles ordinary spin. Like a top, a particle can spin in either of two directions, usually called plus and minus, or up and down. Certain interactions produce a pair of particles that speed off in opposite directions. Regardless of how far apart they get, they remain correlated in the following way: If you measure one for spin, the other particle must have opposite spin.
At first thought you might suppose there is nothing more mysterious about this than tossing two frisbies in opposite directions and giving them opposite spins. But in QM a particle does not have a spin until it is measured. At the moment of measurement its wave function is said to "collapse" and nature decides by chance whether to give the particle a plus or a minus spin. If the other particle is, say, light-years away, the same wave-function collapse will give it an opposite spin. Put another way, the two particles remain a single quantum system with a single wave-function.
The question Einstein asked was this: How does the other particle "know"