Brown's 14 Morphemes
Roger Brown was a pioneer in the systematic, longitudinal observation of toddlers acquiring their native language. Brown and his colleagues tracked the acquisition of 14 closed class morphemes. But, this list of morphemes only skims the surface of grammatical development. Underlying their acquisition is the development of richly detailed grammatical systems, such as the Determiner System of English. The possessive 's and articles 'a' and 'the' are among Brown's 14 morphemes. However, Brown's list ignores other parts of the Determiner System such as possessive pronouns 'my, your, etc.' and demonstrative pronouns 'this, that, these, those', all of which develop at the same time as Brown's 14 morphemes.