Chapter 13

Artificial Intelligence

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Artificial IntelligenceArtificial:

humanly contrived often on a natural model

Intelligence:the ability to apply knowledge to manipulate one's environment or to think abstractly as measured by objective criteria

Clearly, intelligence is an internal characteristic.How can it be identified?

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Thinking Machines A computer can do some things better --and

certainly faster--than a human can: Adding a thousand four-digit numbers Counting the distribution of letters in a book Searching a list of 1,000,000 numbers for

duplicates Matching finger prints

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Thinking Machines BUT a computer would

have difficulty pointing out the cat in this picture, which is easy for a human.

Artificial intelligence (AI) The study of computer systems that attempt to model and apply the intelligence of the human mind.

Figure 13.1 A computer might have trouble identifying the cat in this picture.

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In the beginning… In 1950 Alan Turing wrote a paper titled

Computing Machinery And Intelligence, in which he proposed to consider the question “Can machines think?”

But the question is “loaded” so he proposed to replace it with what has since become known as the Turing Test.“Can a machine play the Imitation Game?”

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The Imitation Game

Skip detailed description

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The Imitation GameThe 'imitation game' is played with three people,

a man (A), a woman (B), and an interrogator (C) who may be of either sex.

The interrogator stays in a room apart from the other two.

The object of the game for the interrogator is to determine which of the other two is the man and which is the woman.

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The Imitation GameThe interrogator is allowed to put questions to A

and B.

It is A's object in the game to try and cause C to make the wrong identification.

The object of the game for the third player (B) is to help the interrogator.

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The Imitation GameWe now ask the question, 'What will happen

when a machine takes the part of A in this game?'

Will the interrogator decide wrongly as often when the game is played like this as he does when the game is played between a man and a woman?

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The Imitation Game

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The Turing Test (objections) There are authors who question the validity of

the Turing test. The objections tend to be of 2 types.

The first is an attempt to distinguish degrees, or types of equivalence…

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The Turing Test (objections) Weak equivalence: Two systems (human and

computer) are equivalent in results (output), but they do not arrive at those results in the same way.

Strong equivalence: Two systems (human and computer) use the same internal processes to produce results.

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The Turing Test (objections) The Turing Test, they argue, can demonstrate weak

equivalence, but not strong. So even if a computer passes the test we won’t be able to say that it thinks like a human.

Of course, neither they, nor anyone else, can explain how humans think!

So strong equivalence is a nice theoretical construction, but since it’s impossible to demonstrate it between humans, it would be an unfair requirement of the Turing Test.

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The Turing Test (objections) The other objection is that a computer might seem to be

behaving in an intelligent manner, while it’s really just imitating behaviour.

This might be true, but notice that when a parrot talks, or a horse counts, or a pet obeys our instructions, or a child imitates its parents we take all of these things to be signs of intelligence.

If a parrot mimicking human sounds can be considered intelligent (at least to some small degree) then why wouldn’t a computer be considered intelligent (at least to some small degree) for imitating other human behaviour?

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Turing’s View “I believe that in about fifty years time it will

be possible to programme computers with a storage capacity of about 109 to make them play the imitation game so well that an average interrogator will not have more than 70 per cent chance of making the right identification after five minutes of questioning.”

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Context In 1950, computers were very primitive.

UNIVAC I was the first commercial computer made in the United States. It was delivered to the United States Census Bureau on March 31, 1951!

At a time when the first computers were just being built, to suggest that they might soon be able to think was quite radical.

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Objections Turing Foresaw1. The Theological Objection 2. The 'Heads in the Sand' Objection 3. The Mathematical Objection 4. The Argument from Consciousness 5. Arguments from Various Disabilities 6. Lady Lovelace's Objection 7. Argument from Continuity in the Nervous System 8. The Argument from Informality of Behaviour 9. The Argument from Extra-Sensory Perception

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Can Machines Think? No machine has yet passed the Turing Test.

Loebner Prize established in 1990 $100,000 and a gold medal will be awarded to the

first computer whose responses are indistinguishable from a human's

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Aspects of AI Knowledge Representation

Semantic Networks Search Trees

Expert Systems Neural Networks Natural Language Processing Robotics