CS 121: Introduction to AI Jean-Claude Latombe ai.stanford/~latombe

CS 121: Introduction to AI Jean-Claude Latombe ai.stanford.edu/ latombe cs121.stanford.edu Required textbook: S. Russell and P. Norvig. Artificial Intelligence: A Modern Approach. 3rd edition, Prentice Hall, 2010 1

Course Assistants Jacob Quain Nikil Viswanathan 2

Office Hours and Sections JCL Mon at 11am-12pm in Gates 135 Jacob Quain Nikil Viswanathan CA section: 3

Today’s Agenda Introduction to AI (Russell and Norvig: Chap. 1 and 2) Overview of CS121 4

What is AI? an attempt of AI is the reproduction of human reasoning and intelligent behavior by computational methods Intelligent behavior Computer Humans 5

What is AI? (R&N) Discipline that systematizes and automates reasoning processes to create machines that: Act like humans Think like humans Act rationally Think rationally 6

Act like humans Think like humans Act rationally Think rationally The goal of AI is to create computer systems that perform tasks regarded as requiring intelligence when done by humans AI Methodology: Take a task at which people are better, e.g.: Prove a theorem Play chess Plan a surgical operation Diagnose a disease Navigate in a building and build a computer system that does it automatically But do we want to duplicate human imperfections? 7

Act like humans Think like humans Act rationally Think rationally Here, how the computer performs tasks does matter The reasoning steps are important Ability to create and manipulate symbolic knowledge (definitions, concepts, theorems, ) What is the impact of hardware on low-level reasoning, e.g., to go from signals to symbols? 8

Act like humans Think like humans Act rationally Think rationally Now, the goal is to build agents that always make the “best” decision given what is available (knowledge, time, resources) “Best” means maximizing the expected value of a utility function Connections to economics and control theory What is the impact of self-consciousness, emotions, desires, love for music, fear of dying, etc . on human intelligence? 9

Can Machines Act/Think Intelligently? “If there were machines which bore a resemblance to our bodies and imitated our actions as closely as possible for all practical purposes, we should still have two very certain means of recognizing that they were not real men. The first is that they could never use words, or put together signs, as we do in order to declare our thoughts to others Secondly, even though some machines might do some things as well as we do them, or perhaps even better, they would inevitably fail in others, which would reveal that they are acting not from understanding, ” Discourse on the Method, by Descartes (1598-1650) 10

Can Machines Act/Think Intelligently? Turing Test: http://plato.stanford.edu/entries/turing-test/ Test proposed by Alan Turing in 1950 The computer is asked questions by a human interrogator. It passes the test if the interrogator cannot tell whether the responses come from a person Required capabilities: natural language processing, knowledge representation, automated reasoning, learning,. No physical interaction Chinese Room (J. Searle) 11

An Application of the Turing Test CAPTCHA: Completely Automatic Public Turing tests to tell Computers and Humans Apart E.g.: Display visually distorted words Ask user to recognize these words Example of application: have only humans open email accounts 12

Can Machines Act/Think Intelligently? Yes, if intelligence is narrowly defined as information processing AI has made impressive achievements showing that tasks initially assumed to require intelligence can be automated But each success of AI seems to push further the limits of what we consider “intelligence” 13

Some Achievements Computers have won over world champions in several games, including Checkers, Othello, and Chess, but still do not do well in Go AI techniques are used in many systems: formal calculus, video games, route planning, logistics planning, pharmaceutical drug design, medical diagnosis, hardware and software trouble-shooting, speech recognition, traffic monitoring, facial recognition, medical image analysis, part inspection, etc. Stanford’s robotic car, Stanley, autonomously traversed 132 miles of desert Some industries (automobile, electronics) are highly robotized, while other robots perform brain and heart surgery, are rolling on Mars, fly autonomously, , but home robots still remain a thing of the future 14

Can Machines Act/Think Intelligently? Yes, if intelligence is narrowly defined as information processing AI has made impressive achievements showing that tasks initially assumed to require intelligence can be automated Maybe yes, maybe not, if intelligence is not separated from the rest of “being human” 15

Some Big Open Questions AI (especially, the “rational agent” approach) assumes that intelligent behaviors are only based on information processing? Is this a valid assumption? If yes, can the human brain machinery solve problems that are inherently intractable for computers? In a human being, where is the interface between “intelligence” and the rest of “human nature”, e.g.: How does intelligence relate to emotions felt? What does it mean for a human to “feel” that he/she understands something? Is this interface critical to intelligence? Can there exist a general theory of intelligence independent of human beings? What is the role of the human body? 16

Some Big Open Questions AI (especially, the “rational agent” approach) assumes that intelligent behaviors are based on information processing? Is this a valid assumption? In the movie I,I,Robot, the most impressive feature of the the movie Robot, the most impressive feature of the IfIn yes, can the human brain machinery solve problems that are inherently robots not their robotsisisfor notcomputers? theirability abilityto tosolve solvecomplex complexproblems, problems,but buthow how intractable blend human-like reasoning with other key of they blendbeing, human-like reasoning other keyaspects aspects Inthey a human where is the interfacewith between “intelligence” andofthe human beings (especially, rest of “human nature”, e.g.: self-consciousness, human beings (especially, self-consciousness,fear fearof ofdying, dying, How does intelligence relate to emotions felt? distinction between right and wrong) distinction between right and wrong) What does it mean for a human to “feel” that he/she understands something? Is this interface critical to intelligence? Can there exist a general theory of intelligence independent of human beings? What is the role of the human body? 17

AI contributes to building an information processing model of human beings, just as Biochemistry contributes to building a model of human beings based on bio-molecular interactions Both try to explain how a human being operates Both also explore ways to avoid human imperfections (in Biochemistry, by engineering new proteins and drug molecules; in AI, by designing rational reasoning methods) Both try to produce new useful technologies Neither explains (yet?) the true meaning of being human 18

Main Areas of AI Knowledge representation (including formal logic) Search, especially heuristic search (puzzles, games) Planning Reasoning under uncertainty, including probabilistic reasoning Learning Agent architectures Robotics and perception Natural language processing Agent Perception Robotics Reasoning Search Planning Natural language Learning Knowledge rep. Constraint satisfaction . Expert Systems 19

Bits of History 1956: The name “Artificial Intelligence” is coined 60’s: Search and games, formal logic and theorem proving 70’s: Robotics, perception, knowledge representation, expert systems 80’s: More expert systems, AI becomes an industry 90’s: Rational agents, probabilistic reasoning, machine learning 00’s: Systems integrating many AI methods, machine learning, reasoning under uncertainty, robotics again 20

Schedule Date Topic HW: Out Due Russell & Norvig textbook (Tue,) Slides (ppt) Slides (pdf) 1/3 Introduction Chap. 1 and 2 1 1 1/5 Search problems Chap. 3, Sections 3.1-2 2 2 1/10 Blind Search Chap. 3, Sections 3.3-4 3 3 1/12 Heuristic search (1/3) Chap. 3, Sections 3.5-7 4-5 4-5 1/17 MLK Day (no class) 1/19 Heuristic search (2/3) Chap. 3, Sections 3.5-7 4-5 4-5 1/24 Heuristic search (3/3) Motion planning (1/2) Chap. 4, Section 4.1 6-7 6-7 1/26 Motion planning (2/2) Chap. 25, Section 25.4 6-7 6-7 1/31 Action planning Chap. 10 8 8 2/2 Constraint satisfaction Chap. 6, Section 6.1 9 9 2/7 Constraint propagation Chap. 6, Sections 6.2-5 10 10 2/9 Introduction to uncertainty Chap. 13, Sections 13.1-2 11 11 2/14 Non-deterministic uncertainty 12 12 2/16 Adversarial Search Chap. 5 13 13 2/21 Presidents’ Day (no class) 2/23 Deciding under probabilistic uncertainty Chap. 16 and 17 14 14 2/28 Bayesian nets Chap. 14 15 15 3/2 Inductive learning (1/2) Chap. 18 16 16 3/7 Inductive learning (2/2) Chap. 18 17 17 3/9 Course review by CAs - Note that HWs are due on Tuesdays at noon (not on Mondays) - Final: Wednesday March 16th at 8:30-11:30am HW1(doc, pdf) HW2(doc, pdf) HW3(doc, pdf) HW4(doc, pdf) HW1 HW2 HW3 HW4 HW5(doc, pdf) HW6(doc, pdf) HW7(doc, pdf) HW5 HW6 HW7 21

CS121 Web Site cs121.stanford.edu ai.stanford.edu/ latombe/cs121/2011/home.htm (homeworks, exam, grading) Required textbook: S. Russell and P. Norvig. Artificial Intelligence: A Modern Approach. 22

157 Logic & Automated Reasoning 222 224M Rational Agency and Intelligent Interaction 227B Reasoning Methods in AI 221 228 226 Structured Probabilistic Models Statistical Techniques in Robotics 224U Natural Language Processing Speech Recognition and Synthesis Multi-Agent Systems 227 General Game Playing 224S 224N 121 223A 225A 225B Intro. to Robotics Experimental Robotics 223B 229 Machine Learning Intro. to Computer Vision 23

Immediate actions: 1. Browse cs121.stanford.edu 2. Register on AXESS as soon as possible 24