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Transcript of Artificial Intelligence
Artificial IntelligenceIan [email protected]
The Turing Test
Artificial IntelligencePart I :Turings Imitation GamePart II: Some sample games from the 60s to the 90sThe Turing Test
Alan M Turing, HeroHelped to found theoretical CS1936, before digital computers existedHelped to found practical CSwartime work decoding Enigma machinesACE Report, 1946Helped to found practical AI first (simulated) chess programHelped to found theoretical AI
Can Machines Think?Computing Machinery and Intelligence Alan M TuringMind, Vol LIX, Number 236 (1950)Can be found reprinted in many placese.g. Computers and Thought
Can Machines Think?Turing starts by defining machine & thinkWill not use everyday meaning of the wordsotherwise we could answer by Gallup pollInstead, use a different questionclosely related, but unambiguousI believe the original question to be too meaningless to deserve discussion
The Imitation GameInterrogator in one roomdigital computer in another roomperson in a third roomFrom typed responses only, can interrogator distinguish between person and computer?If the interrogator often guesses wrong, say the machine is intelligent.Usually done with one machine/person at a time
A sample imitation gameTuring suggests some specimen Q & As:Q: Please write me a sonnet on the subject of the Forth BridgeA: Count me out on this one, I never could write poetryQ: Add 34957 to 70764.(pause about 30 seconds)A: 105621Q: Do you play chess?A: YesQ: I have K at my K1, and no other pieces. You have only K at K6 and R at R1. It is your move. What do you play?(pause about 15s)A: R-R8 mate
What did Turing think? Turing (in 1950) believed that by 2000computers available with 128Mbytes storageprogrammed so well that interrogators have only a 70% chance after 5 minutes of being rightBy 2000 the use of words and general educated opinion will have altered so much that one will be able to speak of machines thinking without expecting to be contradicted
Objections and ResponsesTuring discusses responds to some objections Some of them can be dealt with quite quicklyThe Theological ObjectionMan has a soul, machines do notAT: Can we deny His power to give a soul to a machineHeads in the sandI dont like the idea so I will ignore itArgument from various disabilitiesNo machine can X (e.g. tell right from wrong)AT: Becomes a less powerful argument each day
Some more objectionsLady Lovelaces [Adas] objectioncomputers do whatever we know how to order them to perform, so computers cannot do anything really newAT: Machines constantly surprise us.Argument from informality of behaviourimpossible to write down formal rules for every situationAT: Scientifically impossible to prove people not driven by rulesArgument from ESPTelepathy would let humans win imitation gameAT: Put competitors in telepathy-proof room (!)
Three more serious objectionsArgument from ConsciousnessNo mechanism could feel pleasure, grief AT: Danger of Solipsism AT: Imitation game exists now - in oral examsProbably the most contentious objectionArgument from continuity in the nervous systemthe brain does not operate digitallyAT: computers can simulate continuous behavior, eg. Statistically
Three more serious objectionsMathematical ObjectionGodels theorem, Halting problem, etc, show that machines cannot do meta-reasoning.AT: We too often give wrong answers ourselves to be justified in being very pleased at fallibility of machinesThe mathematical, consciousness, and continuity arguments deserve further discussion, but thats another story
Some Famous Imitation Games1960sELIZARogerian psychotherapist1970sSHRDLUBlocks world reasoner1980s NICOLAIunrestricted discourse1990sLoebner prizewin $100,000 if you pass the test
The problem with ELIZAEliza used simple pattern matching Well, my boyfriend made me come hereYour boyfriend made you come here?Eliza written by Joseph WeizenbaumWeizenbaum so upset at credibility of users his secretary wanted to use it only in privatepsychotherapists excited at prospect of Eliza-booths he wrote a book to debunk the possibilitiesComputer Power and Human Reason
The problem with SHRDLUSHRDLU had a very limited domainLook-ma-no-hands AIhard to abstract lessons learntnatural language processing intermingled with planning, etcSHRDLU written by Terry Winogradwith this and later work, he made major contributions to AIespecially in natural language processing
The problem with NICOLAINICOLAI was not a computer program!Doug Hofstadter conducted dialogue, believing NICOLAI was electronic(Almost) passed the Reverse Turing TestTricks like the occasional dumb answerbut too much cleverness in these weird responses
The problem with the Loebner PrizeJason Hutchens programmed the 1996 winnerThen wrote an articleHow to pass the Turing test by cheating ! Turings imitation game in general is inadequate as a test of intelligence, as it relies solely on the ability to fool people, and this can be very easy to achieve, as Weizenbaum found.
Summary: The Turing TestThe Turing test turns a philosophical question ...Can Machines think? Into an operational oneCan machines play the imitation game?We are not near writing programs to pass the testThe Turing test does NOT drive much AI researchImproving the capabilities of computers DOES
There are some excellent resources on Alan Turing
There is a biography by Hodges, Alan Turing: The Enigma A play of his life is called Breaking the Code.
An excellent web page is maintained also by Hodges.