1 GPS, A Program That Simulates Human Thought 신 동 호신 동 호 Allen Newell & H.A. Simon

2 Contents o Introduction o An Experimental Situation o The Problem of Explanation o The GPS Program o GPS on the Problem o Comparison of the GPS Trace with the Protocol o Summary of the Fit of the Trace to the Protocol o Conclusion

3 Introduction o Psychology of human thinking o To explain how some humans try to solve some simple formal problems o Information processing o Construction of intelligent automata o Distinction between - l the attempt to accomplish with machines the same tasks that humans perform l the attempt to simulate the processes humans actually use to accomplish these tasks

4 GPS o Maximally confuses the two approaches l A problem solving program l Simulations of human behavior

5 History of Psychology o Associationism l atomistic doctrine l hard little elements (sensations or ideas) l associated together without modification l mechanistic doctrine with simple fixed laws of contiguity in time and space l behavior proceeded by the stream of associations l each association produce its successors, and acquired new attachments with the sensations arriving from the environment

6 Cont’d o Wurzburg school l introduced the task(Aufgabe) as a necessary factor in describing the process of thinking l a blend of mechanism and phenomenalism l give rise Behaviorism and the Gestalt movement

7 Cont’d o Behavioristic reaction l introspection is a highly unstable subjective procedure l reformulate task of psychology as explaining the response of organisms as a function of the stimuli o Gestalt reaction l reject the mechanistic nature of observation l thinking is more than association - has direction l holistic principles of organization o Today psychology l stable tension between Behaviorism and Gestalt psychology

8 An Experimental Situation o TASK l (R   P)  (  R  Q) |-  (  Q  P) o Rule 1  8 o Figure 1

9 Protocol(fig2) o Well, looking at the left hand side of the equation, first we want to eliminate one of the sides by using rule 8. It appears too complicated to work with first. Now - no, -no, I can’t do that because I will be eliminating either the Q or the P in that total expression. I won’t do that at first. Now I’m looking for a way to get rid of the horseshoe inside the two brackets that appear on the left and right sides of the equation. And I don’t see it. Yeh, if you apply rule 6 to both sides of the equation, from there I’m going to see if I can apply rule 7.

10 The Problem of Explanation o Find a model of the human problem-solver that explains the salient features of this stream of behavior o Computer is a general manipulator of symbols o The attempts to construct programs that solve tasks requiring intelligence o An intelligent program that manipulates symbols in the same way that our subject does

11 The GPS Program objects operators o GPS deals with a task environment consisting of objects which can be transformed by various operators o operators l detects differences between objects l organizes the information about the task environment into goals o Goal l collection of information that defines what constitutes goal attainment l makes available the various kinds of information relevant to attaining the goal

12 Cont’d o Three types of goals l Transform object A into B l Reduce difference D between object A and object B l Apply operator Q to object A o Symbolic logic l object - logic expression l operator - twelve rules l differences - expressions like “change connective” “add a term” o The objects and operators are given by task, whereas the differences are something GPS brings to the problem

13 Method o GPS is a way of achieving a goal by setting up subgoals, methods is for doing this. o One method associated with each goal type to transform an object A into an object B o Find an operator that is relevant to difference l relevance means that the operator affects objects with respect to the difference o GPS contains an ordering of the differences, so that some differences are considered easier than others.

14 GPS on the Problem o A trace of GPS’s behavior on a specific problem o transform L1 into L0 (fig4)

15 Comparison of the GPS Trace with the Protocol o Protocol l Well, looking at the left-hand side of the equation, first we want to eliminate one of the sides by using rule 8. o GPS l desire to decrease L1 l selection of rule 8 l correspondence with goals 1,2 and 3 of the trace

16 Comparison o Protocol l Now-no,-no, I can’t do that because I will be eliminating either the Q or the P in that total expression. I won’t do that at first. o GPS l GOAL 2 DELETE R FROM L1 l GOAL 3 APPLY R8 TO L1 l PRODUCE L2 R  -P OR -R  Q l GOAL 4 TRANSFORM L2 INTO L0 l GOAL 5 ADD Q TO R  -P OR ADD P TO -R  Q l REJECT

17 Comparison o Protocol l It appears too complicated to work with first. o GPS l nothing is correspondence with this statement

18 Comparison o Protocol l Now I’m looking for a way to get rid of the horseshoe inside the two brackets that appear on the left and right side of the equation. And I don’t see it. Yeh, if you apply 6 to both sides of the equation, from there I’m going to see if I can apply rule 7. o GPS l goals 9 through 14 of the trace

19 Summary of the Fit of the Trace to the Protocol o The program provides a complete explanation of the subject’s task behavior with five exceptions. o Two aspects of disagreements l distinguishing between the internal and external worlds l adequate representation of the spaces in which the search for rules take place o Several recent investigations more generally support the concept of information processing theories of human thinking.

20 Conclusion o Showing that the techniques that have emerged for constructing sophisticated problem-solving programs also provide us with new, strong tools for constructing theories of human thinking. o Associated with Behaviorism and Gestalt movement o The free behavior of a reasonably intelligent human can be understood as the product of a complex but finite and determinate set of laws.