ABSTRACT
This chapter concerns an important aspect of quantitative development, namely the ability to determine amount (“extent”) with respect to a single dimension such as length. Our focus is on measurement ability and its growth with age. Humans have developed schemes for measuring various quantities such as length, overall object size (area and volume), and distance between objects. Quantities obtained using these measures can then be maintained in memory and shared with others. Such schemes specify a system of standards with which amounts can be compared, contributing to accuracy in establishing the values of these amounts. Further, measurement schemes generally allow for the breaking down of continuous dimensions into discrete units that can be used to preserve quantitative information about individual amounts, and to compare among different amounts.
