Ai

Artificial IntelligenceWhat is AI?Issues in AI

An Overview

- AI is a science of making intelligent machines - Intelligence is a type of computation: What is a computation? Turing Machines - How do we know if a machine is intelligent or not? Turing Test

Artificial intelligence is the science and engineering of making computer programs that exhibit characteristics of human intelligence.

Scientific aim: To understand the requirements for and mechanisms of human, animal, machine, robotic intelligence

Engineering aim: To apply such knowledge in building useful artifacts (machines & robots) capable to do things done by humans or animals1. What is AI?

What is intelligence?- Intelligence is the computational part of the ability to solve problems and achieve goals in the world in an efficient manner (McCarthy)- Computational part .. to do efficiently Algorithm

(e.g.) Tower of Hanoi Problem:Tic-tac-toe:Chess: No. of all possible board states: 10120!! - Combinatorial explosion problem- Blind search intractable

Tower of Hanoi

Branches of AIKnowledge representationProcessing information about and representing facts about the world in some abstract wayPattern recognition Extracting knowledge from images (e.g., letters, face, X-ray data, satellite photos)Reasoning and inference Deriving conclusions from premises or incomplete observations (e.g., logical deduction, math theorem proving, medical diagnosis, stock market/weather forecasting)Machine learningImproving performance from experience (e.g., rule induction & adaptive modification)Planning Planning a complex sequence of actions (e.g., playing chess)Natural language processingProduction and interpretation of spoken and written language

Pattern recognition Knowledge representation Reasoning & inference Machine learning

Applications of AIComputer vision- IRIS (biometric identification device), detection of forgeries, chip inspectionExpert systemsMYCIN (medical diagnosis), HYPO (legal reasoning), auto pilot, intelligent tutoring systemGame playing IBMS Deep Blue (search 2m positions per sec)Speech recognition- Dragon Naturally SpeakingRobotics- robot moles in Mars exploration

Dartmouth Workshop (1956)- Summer workshop that officially launched the field known as Artificial Intelligence (named by McCarthy)- Participants included: McCarthy (Stanford), Minsky (MIT), Shannon (Lucent), Newell (CMU), Simon (CMU)

General Problem Solver (GPS) (Newell & Simon, 1960s)- Landmark computer program that solves simple problems/puzzles (e.g., Tower of Hanoi) and even comes up with proofs for mathematical theorems- Based on a general problem solving strategy called the mean-ends analysis (work backward from the goal to decide on what action(s) will help you achieve in which goals are decomposed into subgoals in a recursive fashion)

Weak AI vs Strong AI in the Study of Mind (Searl 1980)

Weak AI: - The principal value of the computer in the study of mind is that it gives us a very powerful tool. Strong AI: - An appropriately programmed computer literally has cognitive states and therefore explains how the human mind works.

Issue #1:

What is a computation?2. Issues in AI

Turing Machines (Turing, 1937)

- A Turing Machine, an idealized, mathematical abstraction of a digital computer, consists of

(1) 1-dim tape of cells of unlimited length (written on each cell is a symbol from finite alphabet)(2) read/write head(3) control (action) table or program

Control program:

- State of head: {S1, S2, S3}- Binary alphabet on tape: {0,1}- Movement of head: {Left, Right}

Condition (IF)Action (THEN)CurrentstateSymbol read Symbol to write Move the head toNew state S1 0 1 Left S3 S2 1 1 Right S1 S3 1 0 Left S2

A Turing machine that computes: 2 x 4 = 8

(Turings) Definition of computation

- A function is said to be computable if it can be implemented on a Turing Machine. - Such functions are called Turing computable functions(e.g., f(x) = 0; natural log e; +/x; if-then) Roughly speaking, a function or task is computable if its solution can be found in finite time (or polynomial time).A problem in which the time required to solve grows exponentially as the problem size grows said to be uncomputable (i.e., unsolvable), thereby requiring infinite time to solve NP-hard problem(e.g., Traveling Salesman Problem)

Traveling Salesman Problem16-city problemA candidate solution

Universal (Turing) Machine- Turing also showed that it is possible to design a single Turing machine that can simulate any Turing machine. Such a machine is called a Universal Turing Machine

Church-Turing Thesis: In essence, A Universal Turing Machine can compute any non-NP-hard problem.(e.g.) - Programmable computers (PC, MaC)von Neumann Machine- program control/action table unit- CPU read/write head unit- RAM - tape- DNA (biological computation device)

Issue #2:

How do we know if a machine is intelligent or not?

Turing Test (Turing, 1951)- First attempt to define an operational definition of intelligence- Turing defined intelligent behavior as the ability to exhibit human-like performance, sufficient to fool an interrogator in an imitation game

Can the Turing test be a definition of intelligence?!%

1. A computer may pass the test but without real understanding of the conversation that took place (e.g., Searls Chinese Room)

2. Many real human beings might fail the test.

3. A computer often exhibits intelligence without being a conversational partner (e.g., autopilot)

Chinese Room (Searle, 1980)- Thought experiment developed as an attack on the Turing Test (againt Strong AI)- Showed that in theory, it is possible to create a system that exhibits intelligent output without understanding (i.e., in the absence of mind), thus passing the Turing test

- Would it be practically possible to build such a system? Why or why not?