Relation between mental age and vocabulary development among children with mild mental retardation.

An investigation of the relation between lexical knowledge and mental age (MA) in elementary school-age children with mild mental retardation was conducted. Lexical knowledge was assessed using the Peabody Picture Vocabulary Test-Revised (PPVT-R) and the Boehm Test of Basic Concepts. Items on the PPVT-R focus on labels for objects and events; items on the Boehm focus on relational terms. Mental age was measured via the Columbia Mental Maturity Scale. Results indicated that the relation between lexical knowledge and MA depended upon the nature of the vocabulary test: The correlation between the Boehm and MA was significantly higher than that between the PPVT-R and MA, suggesting that for this population, MA is more strongly related to knowledge of abstract relational terms than to knowledge of labels for objects and events. The latter may be more open to the influence of differential language experience.