ESPer rating

An ESPer rating was a measurement of the psychic potential of humans. Starfleet Officers were commonly tested and given a rating in the 23rd Century, but this fell out of favor due to the efforts of Section 31, which came to believe that messing with psychic powers was a bad idea unless they were the ones doing it. Ronnie Harper of the SS Clydesdale had a high ESPer rating, which Dr. Janet Corbair took advantage of in an effort to prove that she could give humans enhanced abilities. Corbair was successful, but Ronnie wiped any knowledge of the experiment and went off to explore the universe. ("The Khan Job" [TOS])