Language Development and Assessment in the Preschool Period

Most young children make significant progress in learning language during the first 4 years of life. Delays or differences
in patterns of language acquisition are sensitive indicators of developmental problems. The dynamic, complex nature of language
and the variability in the timing of its acquisition poses a number of challenges for the assessment of young children. This
paper summarises the key developmental milestones of language development in the preschool years, providing a backdrop for
understanding difficulties with language learning. Children with specific language impairment (SLI) are characterised illustrating
the types of language difficulties they exhibit. Genetic evidence for language impairment suggests complex interactions among
multiple genes of small effect. There are few consistent neurobiological abnormalities and currently there is no identified
neurobiological signature for language difficulties. The assessment of young children’s language skills thus focuses on the
evaluation of their performances in comparison to typically developing peers. Assessment of language abilities in preschool
children should involve an evaluation of both expressive and receptive skills and should include an evaluation of more than
one dimension of language. The use of a single measure of a language component, such as vocabulary, is considered inadequate
for determining whether preschool children have typical language or language impairment. Available evidence supports the inclusion
of measures of phonological short-term memory in the assessment of the language abilities of preschool children. Further study
of genetic, neurobiological and early behavioural correlates of language impairments in preschool children is needed.