# Describe Newell’s approach to problem solving. Explain the general problem solving strategies of Wickelgren.

According to Newell’s approach to problem solving, people solve problems by searching in a problem space. The problem space consists of the initial (current) state, the goal state, and all possible states in between. The actions that people take in order to move from one state to another are known as operators. Consider the eight puzzle. The problem space for the eight puzzle consists of the initial arrangement of tiles, the desired arrangement of tiles (normally 1, 2, 3 ….8), and all the possible arrangements that can be arrived at in between.

However, problem spaces can be very large so the key issue is how people navigate their way through the possibilities, given their limited working memory capacities. In other words, how do they choose operators? For many problems we possess domain knowledge that helps us decide what to do.

But for novel problems Newell and Simon proposed that operator selection is guided by cognitive short-cuts, known as heuristics. The simplest heuristic is repeat state avoidance or backup avoidance 1, whereby individuals prefer not to take an action that would take them back to a previous problem state.

This unhelpful when a person has taken an inappropriate action and actually needs to go back a step or more. Another heuristic is difference reduction, or hill- climbing, whereby people take the action that leads to the biggest similarity between current state and goal state.

### Wickelgren argues that there are five general problem solving techniques for searching the state action tree.

Inference: The process of deriving•the strict logical consequences of assumed premises.

State Evaluation and Hill Climbing: State evaluation is evaluating possible operations ,to help determine paths to the goal-expression. Hill climbing is systematically choosing one of these paths.

Sub-Goals: Another strategy that Wickelgren presents is creating “sub-goals”, or breaking the problem into simpler problems.

Contradiction: A third strategy is “Contradiction”, a method of problem-solving in which one proves that the goal could no% possibly be obtained from the givens.

Working Backwards: A fourth strategy is “Working backwards”, an effective strategy for problems that have a uniquely defined goal and for which several givens must be used to derive the goal.

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