Some terran psychics are able to utilize sense psionics to identify other psychics and the aftermath of psionic activity. A ghost, MacGregor Golding, was able to identify an unregistered civilian telepath just by looking at her. In weaker psychics, such as wranglers, this ability manifests as a headache in the presence of another psychic (or the remnants of psychic activity), with an intensity matched by the power of the psychic being detected. The ability can be honed through equipment and (sometimes) other esoteric methods, enabling a psychic to track another one at a distance.
Ghosts generate alpha waves when using psionic abilities (such as their partially psi-generated cloaking field), which can be detected by other ghosts. Sarah Kerrigan used this ability to detect the presence of another ghost in a battle, but could not determine his exact location without technological assistance.
Zerg are sensitive to psionics at a short distance. They can detect particularly powerful psychics at a great distance, further away than a wrangler can. The zerg can sense active psi emitters from a great distance, even across worlds.
The zerg attraction to psionics is poorly understood by the general terran civilian populace, and the impact that neural inhibitors have on this attraction is a point of dispute. At least one psychic, Colin Phash, has developed the ability to hide their psionics from the zerg, though this requires concentration.