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The General Problem Solver

Before the modern era of cognitive research, problem solving was studied mainly through examination of humansd with puzzles. The modern era of computer-based research on problem solving started with the work of Newell and Simon (1963) who designed a computer program called the General Problem Solver (GPS). From that time on, researchers have explored a variety of ways in which computers might conduct problem solving. Cognitive psychologists have used the ideas to explore similar capabilities in humans.

How did the GPS (General Problem Solver) solve problems?

Newell and Simon defined each problem as a space. At one end of the space is the starting point, on the other side is the goal. The problem-solving procedure itself is conceived as a set of operations to cross that space, to get from the starting point to the goal state, one step at a time.

What is "hill-climbing"?

In the General Problem Solver, the program tests various actions (which Newell and Simon called operators) to see which will take it closer to the goal state. An operator is any activity that changes the state of the system. The General Problem Solver always chooses the operation that appears to bring it closer to its goal. This tactic is called hill climbing, because it resembles the tactic of always taking a step toward the top of a hill or mountain. Similarly, humans struggle toward long-term objectives "one day at a time." Progress through school can be represented as a problem space. As you complete each course in your curriculum, you take one step closer to the goal of obtaining a degree. (You may recognize here the pattern of deviation-reducing feedback, discussed earlier in the context of motor activity.)

What is the "foothill problem" in hill climbing?

Hill climbing is a simple strategy, but it does not always work. One potential trap is the "foothill problem." If you are selecting whatever step takes you uphill (or in a particular direction) you might end up climbing a foothill that lies between yourself and the mountain, ignoring the much more efficient procedure of going around it. In other words, if you go straight toward a goal without flexibility, you may pay a steep price, waste a lot of energy, or cause more work for yourself without contributing to the goal. More sophisticated problem-solving programs, such as those that play chess, must look ahead many steps to see potential problems well in advance. That way they can evade hidden traps and inefficient climbs up foothills, on the way to a goal.


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