The Effects of Genetic and Environmental Factors on Writing Development

The Modularity of Dysgraphia

Research regarding dysgraphia, an impairment in writing, is attaining more attention in recent times. The existing studies on dysgraphia draw insights from cognitive, behavioural, neurological, and genetic fields of knowledge. However, these multiple studies on dysgraphia fail to illustrate how these cognitive, behavioural, neurological, and genetic systems interact and intersect in dysgraphia. Therefore, the studies could not offer a comprehensive understanding of dysgraphia. In order to fill this gap, the review attempts to study dysgraphia using the notion of modularity by accommodating insights from cognitive, behavioural, neurological, and genetic aspects of dysgraphia. Such a profound understanding could facilitate an early diagnosis and holistic intervention towards dysgraphia.

Exploring the Influence of Early Childhood Education and Care on the Etiology of Achievement

The present study used a genetically-sensitive quantile regression approach to examine the relation between participation in early childhood education and care (ECEC) and subsequent school performance in literacy and numeracy at grades 3, 5, 7, and 9. The sample consisted of 1255 twin pairs (596 MZ; 659 DZ) with information on both ECEC and the National Assessment Program-Literacy and Numeracy (NAPLAN) scores from the Twin Study of NAPLAN. Results indicated variation in heritability estimates across the distributions of achievement, suggesting that different patterns of etiological influences may exist among children of different ability levels. Additionally, the results provided no evidence that ECEC significantly influenced achievement, and in the genetically-sensitive analyses, no evidence that ECEC moderated the influences of heritability of achievement for typically advantaged children. These results suggest that ECEC may not provide the levels of environmental support for later achievement that advocates claim, although we acknowledge that ECEC quality, which was not measured in the current study, may make a difference in whether or not ECEC influences achievement.

Relationship Between Children's Lexical Diversity in Written Narratives and Performance on a Standardized Reading Vocabulary Measure

The purpose of this study was to examine construct validity of methods of calculating lexical diversity in written narrative samples relative to children's performance on a reading vocabulary measure. For 234 children in 1st-5th grade, written narratives were examined and compared between grades for number of different words (NDW), total words (TNW), NDW in a truncated 50 word sample, and type token ratio (TTR). The relationship between lexical diversity in written narratives and a standardized reading vocabulary measure (GMRT-4) was analyzed by comparing correlations. Grade differences were observed in measures of lexical diversity and productivity. Lexical diversity showed a significant moderate correlation with the GMRT-4. NDW had a stronger relationship to GMRT-4 scores than TTR for participants in first and second grade. Considering length (TNW, NDW constrained to 50 words, or TTR) did not result in a stronger relationship with reading vocabulary. Following additional study establishing probe equivalence, NDW in written narratives may be an efficient, educationally relevant, marker of language maturity and a good predictor of performance on a standardized reading vocabulary measure.