Hardiman, Pollatsek, & Well (1986)

Twenty-two university students who did not initially know the quantitative rule for predicting whether a configuration of weights placed on a balance beam would cause the beam to balance, tip left, or tip right were asked to induce the rule in a training procedure adapted from Siegler (1976). For each of a series of balance beam problems, subjects predicted the action of the beam and explained how they arrived at their prediction. Protocols revealed that although all subjects realized early on that both weight and distance were relevant to their predictions, they used a variety of heuristics prior to inducting the correct quantitative rule. These heuristics included instance-based reasoning, qualitative estimation of distance, and the use of quantitative rules of limited generality. The common use of instance-baded reasoning suggests that learning to understand the balance beam cannot be described completely in terms of a simple rule acquisition theory. Also, the variability in the use of heuristics across subjects suggests that no simple theory that depicts subjects as linearly progressing through a hierarchy of levels can adequately describe the development of balance understanding.