A general strategy for quantity judgments: the height width rule.

Previous work has found that 5-year-olds judge the area of rectangles by a height width rule. Present results indicated that 3- and 4-year-olds also judge area by a height width rule. This adding rule was interpreted in terms of a general-purpose judgmental strategy that young children employ to make quantitative judgments. Both the use of a rating scale and the use of an adding rule in judgment indicate an impressive level of quantitative ability at a very early age.