SLPs are well-aware that speech, language, and literacy are all interconnected, but we’re also aware that they’re not necessarily interconnected in a nice, clear, easy-to-understand way. This study helped to sharpen our vision on whether we should expect later spelling difficulty in children with early speech and language disorders.
First, a quick refresher. There are a couple of skills kids need in order to have good spelling skills. One is phonological awareness. The other is RAN, or rapid automatized naming (e.g., naming a set of colors or animals as fast as possible). While RAN is usually studied in the context of reading, it can also affect spelling, and can predict spelling difficulty in children, especially for irregular words (see here for more on RAN and spelling). In addition to the skills associated with spelling, there is also a genetic factor: spelling difficulty (and reading, learning, language, etc.) can run in families. On top of all of that, we know from existing research and clinical experience that children with speech sound and language disorders are at risk for later reading and spelling impairments.
The authors tested participants from a large longitudinal study to explore how these factors contribute to spelling ability in middle- and high-school students. Children who were tested between 4- and 6-years of age were split into groups* based on diagnosis:
SSD + DLD
CAS (these children also all had DLD)
All children were assessed again at middle school or high school age on phonological awareness, RAN, reading decoding, and spelling. Interestingly, the results indicated that having SSD alone was not associated with spelling difficulty in later school years, but children with SSD + DLD and children with CAS (who also met criteria for DLD) showed continued spelling difficulty into middle- and high-school. Taking a closer look at the underlying skills needed for spelling, phonological awareness was related to spelling scores at middle- and high-school, but RAN was only related to spelling scores in the high school group.
The authors also looked at heritability of spelling skills. Heritability looks at the probability that differences in a trait (in this case, spelling) occur because of genetic reasons and not because of environmental factors or by chance. Controlling for diagnosis and socio-economic status, the authors found strong heritability only in the high school group, meaning that genetic factors are probably more important in later spelling skills while environmental factors are more at play in the earlier years. Based on the results of the study, authors suggest we should keep a close eye on children with early SSD and DLD and intervene for those students who are showing early signs of spelling and reading difficulty.
*SSD = speech sound disorder; DLD = developmental language disorder; CAS = childhood apraxia of speech)
Lewis, B. A., Freebairn, L., Tag, J., Benchek, P., Morris, N. J., Iyengar, S. K., …, & Stein, C., M. (2018). Heritability and longitudinal outcomes of spelling skills in individuals with histories of early speech and language disorders. Learning and Individual Differences. Advance online publication. doi: 10.1016/j.lindif.2018.05.001