This article shows that for 4th & 5th grade children with reading, writing, and/or language difficulty, the use of complex (less common) words as cohesive ties in their writing is much lower than in typically-developing kids. The authors examined two types of cohesive ties: referential (e.g. us, her, these, another, more) and conjunctive (e.g. and, actually, instead, because, then, still). Also, the use of more complex cohesive ties was associated with higher writing quality scores. The authors provide a nice list of all the words they looked at, plus their method of calculating complexity (use this, not just frequency of occurrence, which won't work!), which may serve as good tools for progress monitoring and intervention design. The authors note, “Including cohesive ties as part of language remediation for intermediate-grade children will give them words with the power to connect ideas in writing, promoting syntactic complexity, discourse connectedness, and writing quality.”
Koutsoftas, A.D., & Petersen, V. (2016). Written cohesion in children with and without language learning disabilities. International Journal of Language and Communication Disorders. Advance online publication. doi: 10.1111/1460-6984.12306.