Children's acquisition of the English cardinal number words, a special case of vocabulary development

Abstract

When children become able to produce the cardinal numbers from 1 to 1.000.000.000.000 in words, it is unlikely that they have encountered each and every one of these number vocabulary words, and stored them in semantic memory. Instead, researchers have assumed that children learn a finite set of number words and use their knowledge of the cardinal number system and problem solving abilities to generate the remaining words in the series. However, this assumption has not been tested empirically, and studies have not focused on children's knowledge of the number word series up to one trillion. Researchers have typically studied preschoolers' acquisition of number words up to one hundred, and suggest that after that point, the system is entirely generative. The purpose of the present investigation was to examine school-aged children's abilities to produce number words up to the billions series, document age related changes in number word knowledge, and determine the relation between children's number production skills and their mathematical ability. In two studies, children from grades one, three, five, and seven, equally divided across sex were asked to produce the number names of a randomly selected set of numerals, and then count from the numeral in a forward or backward direction. Children also completed tasks aimed to assess the size of their basic number word vocabulary and problem solving capabilities. The times taken to produce number words were also recorded in Study 2. Results revealed that children's total cardinal number word vocabularies strongly increased with grade; and children in grades one, three, five, and seven could name and count numbers as high as the hundreds, thousands, millions, and billions series, respectively. Study 2 also demonstrated that children became increasingly proficient in producing number names with grade, as the times taken to name and count numbers within each number series strongly decreased with grade. However, there was a wide range of individual differences within grade, which were related to children's mathematical achievement in most grades. Furthermore, results indicated that children's total number word vocabularies were not only dependent on the size of their basic vocabularies, but were also affected by their knowledge of the compounding rules, and their understanding of the cardinal number system. These findings are discussed in relation to children's mathematical accomplishments during the school years and have implications for the teaching of mathematics in the classroom.