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findings, the developmental trajectories of these groups revealed delayed social and
communication development for the ASD group between 14 and 24 months. Landa
and colleagues also identified different developmental trajectories in the subgroup
who received an early diagnosis (a working diagnosis at the 14 month assessment)
and those who received a diagnosis at the later 24 month assessment. For this latter
group, some skills continued to grow but at a slow rate between the two time points,
others plateaued, whilst others decreased (shared positive affect and gestures). This
would be consistent with the commonly (retrospectively) reported phenomenon of
regression or loss of skills and is taken up later on in this review. Sullivan et al.
(2007) continued this line of research by examining the behavior of response to joint
attention at 14 and 24 months in this cohort of high- and low-risk siblings. Results
indicated that at 14 months the ASD and BAP groups were indistinguishable from
each other and performed less well on several joint attention tasks than the non BAP
group. However by 24 months the ASD group performed less well on the joint
attention tasks than both the BAP and non BAP groups. Furthermore, joint attention
skills at age 14 months predicted both language ability and the outcome diagnosis of
ASD.
Working in California, Sally Ozonoff, Sally Rogers and Marian Sigman are
conducting a large scale prospective study of siblings of children with autism. Nadig
et al. (2007) reported that at age 6 months, no significant differences were found
between SIBS-A and SIBS-TD in their orienting to their name calling. However, at
age 12 months all SIBS-TD (100%) oriented on the first or second call of their name
compared to 86% of the SIBS-A. Furthermore, 75% (n = 9) of the SIBS-A who failed
to respond to their name being called at age 12 months were identified at age 24
months with ASD (n = 5) or with other developmental delays (n = 4). Thus, these