The Foundations of Artificial Intelligence

Our Working Definition of AI Artificial intelligence is the study of how to make computers do things that people are better at or would be better at if: they could extend what they do to a World Wide Web-sized amount of data and not make mistakes.

Why AI? "AI can have two purposes. One is to use the power of computers to augment human thinking, just as we use motors to augment human or horse power. Robotics and expert systems are major branches of that. The other is to use a computer's artificial intelligence to understand how humans think. In a humanoid way. If you test your programs not merely by what they can accomplish, but how they accomplish it, they you're really doing cognitive science; you're using AI to understand the human mind." - Herb Simon

A Time Line View the time linetime line

The Dartmouth Conference and the Name Artificial Intelligence J. McCarthy, M. L. Minsky, N. Rochester, and C.E. Shannon. August 31, "We propose that a 2 month, 10 man study of artificial intelligence be carried out during the summer of 1956 at Dartmouth College in Hanover, New Hampshire. The study is to proceed on the basis of the conjecture that every aspect of learning or any other feature of intelligence can in principle be so precisely described that a machine can be made to simulate it."

The Origins of AI Hype 1950 Turing predicted that in about fifty years "an average interrogator will not have more than a 70 percent chance of making the right identification after five minutes of questioning" Newell and Simon predicted that "Within ten years a computer will be the world's chess champion, unless the rules bar it from competition."

Symbolic vs. Subsymbolic AI Subsymbolic AI: Model intelligence at a level similar to the neuron. Let such things as knowledge and planning emerge. Symbolic AI: Model such things as knowledge and planning in data structures that make sense to the programmers that build them. (blueberry (isa fruit) (shape round) (color purple) (size.4 inch))

The Origins of Subsymbolic AI 1943 McCulloch and Pitts A Logical Calculus of the Ideas Immanent in Nervous Activity “Because of the “all-or-none” character of nervous activity, neural events and the relations among them can be treated by means of propositional logic”

The Origins of Symbolic AI Games Theorem proving

Knowledge Acquisition Hand CraftedMachine Learning Symbolic Subsymbolic

What Are the Components of Intelligence?

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Image Perception

But We’re Still Ahead

But We’re Still Ahead

Reasoning We can describe reasoning as search in a space of possible situations.

Recall the 8-Puzzle What are the states? Start state Goal state

Hotel Maid States: Start state: Operators: Goal state:

The British Museum Algorithm A simple algorithm: Generate and test But suppose that each time we end a path, we start over at the top and choose the next path randomly. If we try this long enough, we may eventually hit a solution. We’ll call this The British Museum Algorithm or The Monkeys and Typewriters Algorithm

Branch and Bound Consider the problem of planning a ski vacation. Fly to A $600Fly to B $800Fly to C $2000 Stay D $200 (800) Stay E $250 (850) Total cost (1200)

Problem Reduction Goal: Acquire TV Steal TVEarn MoneyBuy TV Or another one: Theorem proving in which we reason backwards from the theorem we’re trying to prove.

What is a Heuristic?

Example From the initial state, move A to the table. Three choices for what to do next. A local heuristic function: Add one point for every block that is resting on the thing it is supposed to be resting on. Subtract one point for every block that is sitting on the wrong thing.

A New Heuristic From the initial state, move A to the table. Three choices for what to do next. A global heuristic function: For each block that has the correct support structure (i. e., the complete structure underneath it is exactly as it should be), add one point for every block in the support structure. For each block that has an incorrect support structure, subtract one point for every block in the existing support structure.

Hill Climbing – Another Example Problem: You have just arrived in Washington, D.C. You’re in your car, trying to get downtown to the Washington Monument.

Hill Climbing – Some Problems

Hill Climbing – Is Close Good Enough? A B Is A good enough? Choose winning lottery numbers

Hill Climbing – Is Close Good Enough? A B Is A good enough? Choose winning lottery numbers Get the cheapest travel itinerary Clean the house

The Silver Bullet? Is there an “intelligence algorithm”? 1957GPS (General Problem Solver) Start Goal

The Silver Bullet? Is there an “intelligence algorithm”? 1957GPS (General Problem Solver) Start Goal What we think now: Probably not

But What About Knowledge? Why do we need it? How can we represent it and use it? How can we acquire it? Find me stuff about dogs who save people’s lives.

But What About Knowledge? Why do we need it? How can we represent it and use it? How can we acquire it? Find me stuff about dogs who save people’s lives. Two beagles spot a fire. Their barking alerts neighbors, who call 911.

Expert Systems Expert knowledge in many domains can be captured as rules. Dendral (1965 – 1975) If: The spectrum for the molecule has two peaks at masses x 1 and x 2 such that: x 1 + x 2 = molecular weight + 28, x is a high peak, x 2 – 28 is a high peak, and at least one of x 1 or x 2 is high, Then: the molecule contains a ketone group.

To Interpret the Rule Mass spectometry Ketone group:

Expert Systems in Medicine 1975Mycin attached probability-like numbers to rules: If: (1) the stain of the organism is gram-positive, and (2) the morphology of the organism is coccus, and (3) the growth conformation of the organism is clumps Then: there is suggestive evidence (0.7) that the identity of the organism is stphylococcus.

Watson How does Watson win? Watch a sample round: From Day 1 of the real match: Introduction: IBM’s site: Bad Final Jeopardy: Explanation:

Expert Systems – Today: Medicine Expert systems work in all these areas: arrhythmia recognition from electrocardiograms coronary heart disease risk group detection monitoring the prescription of restricted use antibiotics early melanoma diagnosis gene expression data analysis of human lymphoma breast cancer diagnosis

Dr. Watson A machine like that is like 500,000 of me sitting at Google and Pubmed.

But What About Things That All of Us Know?