The Turing Test is a proposal for a test of machine capabilities described by Alan Turing in 1950. It proceeds as follows: a human judge engages in a natural language conversation with other parties; if the judge cannot reliably tell whether the other party is human or machine, then the machine is said to pass the test. It is assumed that both the humans and the machine try to appear human.
The origin of the test is a party game where guests try to guess the gender of a person in another room by writing a series of questions on notes and reading the answers sent back. In Turing's original proposal, the human participants had to pretend to be the other gender, and the test was limited to a five-minute conversation. These features are nowadays not considered to be essential and are generally not included in the specification of the Turing test.
Turing proposed the test in order to replace the emotionally charged and for him meaningless question "Can machines think?" with a more well-defined one.
Turing predicted that machines would eventually be able to pass the test. In fact, he estimated that by the year 2000, machines with 109 bits (about 119MB) of memory would be able to fool 30% of human judges during a 5-minute test. He also predicted that people would then no longer consider the phrase "thinking machine" contradictory. He further predicted that machine learning would be an important part of building powerful machines, a claim which is considered to be plausible by contemporary researchers in Artificial Intelligence.
It has been argued that the Turing test can not serve as a valid definition of machine intelligence or "machine thinking" for at least two reasons:
- A machine passing the Turing test may be able to simulate human conversational behavior, but this may be much weaker than true intelligence. The machine might just follow some cleverly devised rules.
- A machine may very well be intelligent without being able to chat like a human.
On the other hand, the intelligence of fellow humans is almost always judged exclusively based on their utterances.
So far, no computer has passed the Turing test as such. Simple conversational programs such as ELIZA have fooled people into believing they are talking to another human being, such as in an informal experiment termed AOLiza. However, such "successes" are not the same as a Turing Test. Most obviously, the human party in the conversation has no reason to suspect they are talking to anything other than a human, whereas in a real Turing test the questioner is actively trying to determine the nature of the entity they are chatting with. Documented cases are usually in environments such as Internet Relay Chat where conversation is highly stilted and meaningless comments showing no understanding of the conversation are common. Additionally, many relay chat participannts have English as a second or third language, thus making it even more likely that they assume that a stupid comment by the conversational program is simply something they have misunderstood, and are also probably unfamiliar with the technology of "chat bots" and don't recognize the very non-human errors they make. See ELIZA effect.
The Loebner prize is an annual competition to determine the best Turing test competitors.
- Alan Turing, "Computing Machinery and Intelligence", Mind, vol. LIX, no. 236, October 1950, pp. 433-460. Online at:
- Loebner prize home page