| This thesis examines language development in Jacobsen syndrome (JS), a disorder caused by a microdeletion on the 11th chromosome. JS results in a distinctive facial appearance, physical abnormalities and affects cognition and language.;The cross-sectional study had 23 participants (1--18 years), who were administered the MacArthur Inventories (Fenson et al. 1993), testing vocabulary and early grammatical development (comparable to typical development (TD), 8--30 months), and the Minnesota Child Development Inventory (MCDI) (Ireton, 1992), testing expressive and receptive language (TD, 1--6 years). Cognitive test results were also obtained for about half the participants. The longitudinal study involved one child from 3;0--6;8, with videotapes made at home, the MCDI, and cognitive testing performed at school. The videotapes were analyzed for MLU (Brown, 1973) and grammatical development (Index of Productive Syntax (IpSyn) (Scarborough, 1990) (TD, 2--4 years).;The issues were: (1) extent of delay and intra-domain language differences; (2) effect of socioeconomic status and (3) the relationship between deletion size and language development and (4) between language and non-verbal cognition.;The cross-sectional data reflected significant delays in acquisition in all domains examined but no significant intra-domain differences. The children from families with higher socioeconomic status demonstrated better language skills, according to some measures, than children with lower socioeconomic status. Deletion size correlated with most of the language measures, decreasing with advance in language age, possibly because only two participants had large deletions, where the greatest deficits were observed. These data show language in JS to be as affected or more affected than non-verbal cognition. The longitudinal participant's language was better than non-verbal cognition, however; and a similar profile might apply to at least one other JS participant whose language ability was above the levels tested in this study, indicating the need for further study.;MLU analysis showed early word combinations at a vocabulary size of 50--100 words, consistent with TD but a lengthy plateau in MLU (47--61 months), after which MLU advanced in a more typical fashion. The IpSyn analysis reflected intradomain dissociations. These were partially accounted for by a formulaic strategy, use of phonologically indeterminate blends, and by a language processing overload explanation. |
