“…However, the National Assessment of Educational Progress (NAEP; 2002, 2011; NAEP is the largest nationally representative assessment of what American students know and can do in various subjects) results show that only 28% of fourth graders and 27% of eighth graders perform at or above proficient level in writing. Concerns over low levels of writing achievement in elementary and middle school, together with evidence that children with writing disabilities are at greatly enhanced risk of difficulties in reading and math (Mayes & Calhoun, 2006; Sumner, Connelly, & Barnett, 2013), have motivated a large body of work to identify the sources of individual variability in writing (Abbott & Berninger, 1993; Arfe, Dockrell, & De Bernardi, 2016; Babayigit, 2014; Berninger et al, 1992, 2002; Graham, Berninger, Abbott, Abbott, & Whitaker, 1997; Graham, McKeown, Kiuhara, & Harris, 2012; Kim et al, 2011; Kim, Al Otaiba, Folsom, Greulich, & Puranik, 2014; Kim, Al Otaiba, Wanzek, & Gatlin, 2015; Kim, Park, & Park, 2013; Limpo & Alves, 2013; Olinghouse, 2008; Olinghouse, Graham, & Gillespie, 2015). One line of research that would further clarify variability in writing in elementary and middle school is investigating the etiological (genetic and environmental) factors associated with individual differences in writing.…”