ABSTRACT
M. E. Libertus and E. M. Brannon discovered a method of studying individual differences in magnitude comparison in babies. Intriguingly, they found that individual differences in babies’ numerical preference scores for changing versus stable number stream predicted scores at age 3.6 on the Test of Early Mathematical Ability, non-symbolic number comparisons and the cardinal word principle. One possibility is that both subitizing and approximation are present from the beginning, and that both are important foundations for later arithmetical development. Some people suggest that subitizing and counting are two quite different phenomena, represented in different ways in the brain. J. Piaget considered that children do not really understand number until they are 6 or 7 years old, and that until that age, counting is just a rote procedure. The ability to compare quantities was considered by Piaget to be one of the most central measures of the understanding of quantity.
