Reading acquisition is based on a set of preliteracy skills that lay the foundation for future reading abilities. Phonological awareness--the ability to identify and manipulate the sound units of oral language--has been reported to play a central role in reading acquisition. However, current evidence is mixed with respect to its universal…

Background: Children ordinarily begin their formal education at the age when the great majority of them are capable of understanding the role of addition and subtraction in changing number. In determining critical differences they can apply the oddity principle--the first "pure" abstraction that children ever develop--understanding that…