**Acknowledgements**

ASD symptoms or other developmental impairments [70]. These studies are not included in Table 1 because participants included children with ASD. Nevertheless, their findings with respect to social communication and language are relevant to the understanding of BAP. A number of those research projects have shown that some siblings of individuals with ASD demonstrate observable communication deficits already in the first three years of life and that these impairments can change over time. They include, among others, lower receptive language scores, delayed receptive and expressive language [15, 71-74], requesting behavior [75, 76], understanding words and phrases, gesture use, and social-communicative interactions with parents [77]. The important question is how early are those problems manifested. It was shown that at 6 months of age there were no statistically significant group differences in language development between high risk (HR, children having sibling with autism) and low risk (LR) infants (no autism history in family) [15, 78]. No differences in gaze following were found in children of 7 and 13 months between HR and LR groups [79]. Georgiades et al. [80] concluded that pragmatic language deficits were not relevant traits of BAP at 12 months. Obviously, this does not mean that HR children experience no deficits in language develop‐ ment at that age. Ozonoff with colleagues [78] found atypical language development in highrisk infants of 12 months of age. Differences in language between HR and LR infants of 24 months of age are found much more often [15, 73, 74]. Longitudinal studies are the most desirable as they offer insight into the dynamics and changes in the development of these children. While problems are overcome in some, in others they persist at later stages. As demonstrated by Gamliel et al. [71], expressive and receptive language deficits were still present in HR children at 54 months of age despite the resolution of some other developmental problems. Another important issue is to find out how many of 24-months old HR siblings demonstrating language difficulties are eventually diagnosed with ASD. Hudry et al. [81] found that reduced receptive vocabulary advantage in high risk infants at 14 months, main‐ tained to 24 months only in the subgroups of ASD or other atypicality outcome. This suggests a close to typical development of other children in the HR group. The results of these sample

studies on HR infants expose gaps in the knowledge on the issue.

on selected subgroups of parents and siblings.

criteria, as well as specifics of control groups (Cf. [19]).

Currently, it is difficult to identify universal, clear regularities relating to social communication and language deficits in parents or siblings of children with autism, but they have been found in some subgroups. A more complete knowledge in that area can contribute to a better understanding of autism. It can also provide hints for future research, by focusing attention

There are many reasons for the variation in empirical results discussed in this section. Specific ones include methodological considerations such as sample size, research methods, enrolment

It would be difficult to identify the components of BAP in terms of social communication and language based on currently available data. The best documented aspect of BAP appear to be

**3. Conclusions**

104 Autism Spectrum Disorder - Recent Advances

This paper was funded by the project of the National Science Center in Poland, #UMO-2011/03/ B/HS6/03326.
