It was a paper by J. M. Hurst about unknown drivers that might influence market cycles.
In 1987 I read a paper written by J. M. Hurst, a retired aerospace physicist. He spent some 20,000 hours analyzing economic time-series using tools from his career in research and development.
Hurst theorized the existence of an unknown exogenous or external factor that was actually driving market cycles. He called it “X motivation.”
Hurst said, “… we must admit the possibility that something causes millions of investors operating from widely differing locations, making countless buy and sell decisions, at varying points in time, to behave more or less alike — and to do so consistently and persistently! How can this be?”
He went on, “The answer to this is not known, although reasonable theories can be formulated. If such an exogenous driver can influence some physical and mental functions, might they not influence others — perhaps causing masses of humans to feel simultaneously bullish or bearish in the market, for example?”
Hurst’s “X motivation” is what I now know today to be gravity. As Einstein noted, “gravity is the greatest force known in the universe.”