Developmental psychology.pdf

214 Learning and Information Processing
Figure 8.10
A Flowchart. The circles show
starting and stopping points; the
rectangles indicate computations;
and the diamond indicates a decision
point (Adams & Haden, 1976).
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Sometimes an algorithm is more readily understood when it is presented
graphically, and a diagram is constructed. In this sequential diagram, called a flowchart,
the lines show the order of the steps to be taken and geometric figures show the
activities involved. Each step has its consequence, which leads directly to the next step,
or it leads to a subgoal and thence back to the basic sequence. Onee the flowchart has
been constructed with all possible steps and outcomes, any appropriate problem can
be readily solved (Figure 8.10).
Heuristic Methods Algorithms have their limitations, and therefore human beings
also use other modes of problem solving. It has been estimated, for example, that there
are 10 120 possible moves in a chess game and 10 40 possible moves in checkers. There
are more possible moves in chess, so the saying goes, than atoms in the universe, and
it would take the fastest computer centuries to evaluate each of them. No one can
consider all of these alternatives, even in many lifetimes, and so the chess player, lawyer,
truck driver, and others confronted with typical human problems use heuristic methods
instead. In a heuristic method the problem solver uses the approach most likely to yield
the correct solution, rather than a purely systematic search of all possibilities. Methods
that have been successful in the past serve as guides for the future. Heuristic methods
are strategies or rules of thumb that can speed the solution. The lawyer, truck driver,
and chess player consider the most plausible hypotheses first, and they proceed on that
basis. If not, lawsuits would never end, and trucks would never get out of the city, much
less across the country. Human beings generally deal with their problems through
heuristics.
One problem for psychologists and computer scientists interested in the simulation
of human thought is to program a computer to use heuristic methods, and several
such models have been constructed. In one instance a research team developed
the Logic Theorist, a computer model that simulated human thought by ignoring the
less likely alternatives. It provided proofs for 73 percent of the theorems in Newton's
Prindpia Mathematica without considering all of the possibilities at each step, for a
completely exhaustive search would have required hundreds of years (Newell, Shaw,
& Simon, 1958).