L19JDM1.6slides

# L19JDM1.6slides - Basic logic of Means-end analysis Issues:...

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1 Page 1 1 Issues: (a) Representing problems (b) Methods & common flaws in problem solving (c) Expertise 1. Problems and problem representation Well-structured vs. ill-structured problems Stages in problem solving The importance of problem representation 2. Common flaws in problem solving Analogies Hindrances to forming appropriate representations 3. Problem solving methods Algorithms and heuristics Heuristics: Hill climbing, means-ends analysis, working backward 4. Expertise Very domain specific (chess study) Power law of practice Characteristics of expertise 2 Basic logic of Means-end analysis Match current state to goal state to find the most important difference Subgoal: Eliminate the difference Difference detected SUCCESS SUCCESS No Differences FAIL FAIL Search for operator relevant to reducing the difference Match condition of operator to current state to find most important difference Subgoal: Eliminate the difference SUCCESS No Differences FAIL None found Apply Operator Difference detected Flowchart 1: Transform current state into goal state Flowchart 2: Eliminate a difference 3 IF the peg 3 is clear and the largest disk is free THEN move the largest disk to peg 3. IF the largest disk is not free, THEN set a subgoal to free it. IF a subgoal is to free the largest disk and a smaller disk is on it, THEN move the smaller disk off. Productions for Tower of Hanoi 4 Transform goal state so it is more similar to the initial state. Useful if too many paths leading from initial state. Initial State Goal State 5 useful for mazes: 6 A B C D A geometry problem: Given that ABDC is a rectangle, prove that AD and CB are congruent. Start at end: what would make AD and CB are congruent?

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2 Page 2 7 8 9 Airport example: Largest difference was the final step We solved the entire problem from the end backward before even taking our first step. Gives impression that a problem-solver is contemplative, doing everything in head before taking action. Probably not accurate for many problems. 10 Expertise usually helps ability to solve problems. More experience Better representations More practice solving problems But can sometimes harm: Functional Fixedness Water jug ‘mental set’ 11 Beginners Masters Beginners Masters Actual board positions Random board positions Number correct 12 Beginners Masters Beginners Masters Actual board positions Random board positions
3 Page 3 13 In chess study, experts memory was no better than beginners. Memory for meaningful configurations much better. Memory for random configurations slightly worse (probably hindered by schemas) Chess masters know 50,000 chess patterns. Chess masters intentionally study these patterns.

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## L19JDM1.6slides - Basic logic of Means-end analysis Issues:...

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