Editorial: Special edition on Williams Syndrome.

03Original abstract

Upon deciding that there was a timely need to put together a special edition of JIDR on the topic of Williams Syndrome, we were pleasantly surprised at the vast number of submissions from researchers across the globe. We were immediately faced with the (very pleasant) task of reviewing over 30 submissions on such a wide variety of aspects of this relatively rare developmental disorder. We probably should not have been surprised by the volume of submissions given the number of peer reviewed journal articles published annually on aspects of cognition and behaviour associated with Williams Syndrome. Since the 1980s and 1990s, when the Williams Syndrome first captured the attention of cognitive scientists interested in utilising the uneven cognitive profile to prove (or disprove!) arguments for modularity of mind (e.g. Paterson et al. 1999), to more recent focus on the developmental trajectory of cognition in the disorder, heterogeneity of functioning or the gregarious social profile, there is now a wealth of literature exploring aspects of functioning in Williams Syndrome. In 2015, Web of Science reports 106 articles with the words ‘Williams Syndrome’ in the title, of which 30 focus on the ‘psychological’ aspects of the disorder. Furthermore, specific to JIDR, Williams Syndrome features as a keyword in over 25 articles published in this outlet since 2000 from research groups across the globe. The papers accepted for this edition illustrate the breadth of research questions and approaches characteristic of studies of Williams Syndrome and, more broadly, the study of developmental disorders. While the first psychological studies focused on the cognitive architecture associated with Williams Syndrome and characterised the uneven verbal versus spatial profile (e.g. Wang & Bellugi, 1994), we see that the current selection of manuscripts addresses a significantly broader range of strengths and weakness of not only cognition and language (e.g. Van der Heuvel et al., Fisher et al.), but also motor skill (e.g. Berencsi et al., Heiz et al.), social functioning (e.g. Lough et al., Plesa Skwerer et al.) and aspects of clinical relevance for potential intervention (e.g. Pitts et al.). These issues are studied with a range of novel and innovative methodologies showing advances in the field. Behavioural tasks are used in many of the studies, and these often occur alongside insights from parents (e.g. Fisher et al.) and the addition of eye tracking (e.g. Hirai et al.) or neuropsychological methods (e.g. visual event-related potentials; Key et al.). The papers in this edition address questions of both ‘typicality’ of performance/behaviour (e.g. Goldman et al.) and ‘syndrome-specificity’, for example taking a cross-syndrome approach with the involvement of individuals with Down Syndrome (e.g. Plesa Skwerer et al.). This variety of methodological approaches to core research questions on cognition and behaviour associated with Williams syndrome allows us to understand not only components of this disorder, but also to utilise Williams syndrome to also address theoretically relevant questions for other neurodevelopmental disorders and typical development. Of particular relevance is the fact that the papers included in this edition address two current ‘hot topics’ in the field, namely developmental change and within-syndrome individual differences. In terms of developmental change, at least two of the manuscripts take a longitudinal perspective to study change over time in language and cognition (Fisher et al. and Van der Heuvel et al.). Studying the same individuals over time [rather than either (1) studying a group at one timepoint or (2) studying different individuals at different ages and taking a cross-sectional approach] is particularly useful for our understanding of the development of core skills such as language, and also allows us to consider more precisely the time when potential intervention may be required. This approach provides further insight into arguments of developmental delay or deviance. By taking this approach, we also benefit from the acknowledgement that not all individuals with the same developmental disorder may be following the same developmental trajectory (a potential pitfall of cross-sectional trajectory designs), and that vast within-syndrome differences of development are highly likely. However, such approaches are also extremely time consuming and costly. The second key issue of individual differences is not only addressed in the previously mentioned longitudinal studies, but also specifically feeds into the study of clinical aspects of the disorder in this edition, for example predictors of specific phobia (Pitts et al.). When working with relatively rare groups with developmental disorders, small sample sizes are often an issue, and this is often overcome by the inclusion of a broad age range within the research (a characteristic of a number of studies in this edition). However, an issue that is hindered by the use of small samples is the ability to have the power to explore within-syndrome heterogeneity, which we know exists in terms of both cognition (e.g. Porter & Coltheart 2005; Paterson et al. 1999) and behaviour (e.g. Little et al. 2013). This remains a challenge for the field of developmental disorders, and it is encouraging to see a number of manuscripts in this addition beginning to tackle this issue. After all, while this variability presents as a significant challenge for our research, it also poses the opportunity to explore mechanisms underlying performance/behavioural differences and to consider individual responses to treatment/intervention. It is therefore possible to see both (1) the common themes and (2) the broad variety of topics and approaches that come together in this special edition of JIDR dedicated to Williams Syndrome and it has been a pleasure to see the vast array of active research within this field. While there has been a great deal of research dedicated to some aspects of the disorder, there still remain areas where research, and evidence are lacking. For example, there were no submissions dedicated to ageing in Williams syndrome, and very few focused on interventions to provide a more applied insight. We hope that this special edition not only shows how far the field has developed in terms of understanding aspects of cognition and behaviour in Williams syndrome, but also inspires future research/researchers within this area.

Journal of intellectual disability research : JIDR, 2016 · doi:10.1111/jir.12337