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Specific Language Impairment 76
6.2 Delayed and impaired language development
Children with language impairment often were “late talkers”. These produce their first
words relatively late and have a vocabulary of less than 50 different words at the age of
24 months. In contrast, children with TLD usually acquire these 50 words much earlier
(around 18 to 19 months) and have a vocabulary of around 300 words at 24 months. It
enables them to produce their first two-words-sentences (cf. Leonard, 1998). 12-20
percent of all children did not reach the 50-words-threshold at 24 months. Around half
of these children are “late bloomers”. They return to normal levels of language proficiency
by the end of the third year of life. The remaining half of the children shows a
delayed language development and is mostly diagnosed as having specific language
impairment. Approaching the 50-words-threshold leads to a differentiation of the vocabulary
and the acquisition of syntactic regularities (see chapter “Language perception”).
Thus, the delay children have in their language development may intensify during
further development. Thus, an idea put forward by Leonard (1991) was to conceive
SLI not as impairment but the lower end of a normal distribution (also cf. Tomblin &
Pandich, 1999). That is, SLI children are assumed to acquire their first words and word
combinations later than age-controls but otherwise to mirror the patterns of normally
developing children.
Pre-schoolers with SLI usually are characterized by their limited speech production
(whereas their language perception is much better developed); by their late acquisition
of first words and word combinations; and by their special difficulties with phonological,
morphological, and syntactic structure. For most SLI children, there seems to exist a
relatively monotonic distance between the level of language perception and speech
production (cf. Grimm, 2003). However, semantic and pragmatic abilities were found to
be relatively intact (but see the discussion in Tomblin & Pandich, 1999), even though,
they may have some word finding difficulties indicated by pauses, non-specific words
(“stuff”, “thing”) and phonological and semantic word substitutions.
One of the main characteristics of SLI children are their syntactical and morphological
deficiencies. Their problems may be especially severe for grammatical morphology:
The use of most grammatical morphemes is lower and mastery is attained later in children
with SLI. It remains unclear, if these morphosyntactic deficiencies should be characterized
as quantitative (i.e., SLI children show intact grammatical knowledge but are
delayed in its acquisition) or as qualitative difference (cf. Grimm, 2003; Leonard, 1998).
Children with SLI use specific syntactic structures less frequently than age-controls and
perform worse on measures that concern syntactic complexity and syntactic comprehension
(e.g., reversible passives). Even though they use most argument structures, there is