Extrasensory perception or Esper commonly abbreviated ESP, is a catchall term of any of a number of abilities. Generally, it refers to the ability to perceive using any means other than the five basic senses of sight, hearing, smell, taste, and touch. Those with ESP are sometimes referred to as having "esper-capacity" by some psychologists, who measure it with an "esper rating". (TOS: Where No Man Has Gone Before)
There are a number of more specific terms:
- Clairvoyance is the ability to see at a distance, using the mind. Distant locations are not viewed through the eyes, but are presumably processed within the brain as if they had been.
- Clairaudience is the ability to hear at a distance, using the mind. Distant locations are not heard through the ears, but are presumably processed within the brain as if they had been.
- Precognition is the ability to perceive the future. Precognition is usually unreliable; the assumed explanation for this is that the future is always changing, and what the precognative individual actually perceives is events that are likely to occur. The Yattho are known for this ability. (VOY: "Before and After")
- Retrocognition is the ability to perceive the past. Retrocogntion is often more reliable than precognition, but as it is useful mostly to detectives and other investigative types, it does not often appear in science-fiction.
Some individuals classify telepathy as extrasensory perception, but as with anything that hasn't actually been proved, this is more a matter of opinion. Technically, it meets the definition, since a telepath does not use his ears to listen to the conversation. Some purists, however, prefer to reserve ESP to refer only to abilities related to sensing one's surroundings (however distant).
Individuals with pure ESP cannot affect what they perceive any more readily than anyone else at their location could. However, after Gary Mitchell developed ESP and psychokinesis, he was able to use his ESP to direct a psychokinetic attack on engineering officer Lee Kelso.
Means of gauging ones potential abilities of ESP during the 23rd century, could be determined by the measurements determined in ones esper rating, aperception quotient, Duke-Heidelburg quotient and general knowledge quotient. (TOS: "Where No Man Has Gone Before")
See also: