Background
The lexical quality hypothesis proposes that successful reading comprehension requires high quality lexical representations, which allow for efficient retrieval. These retrieval operations have however not been specified.

Methods
We investigated the contribution of semantic retrieval to reading comprehension in 119 Dutch children in the upper grades of primary school, while taking decoding skills and vocabulary size into account in a longitudinal design. By using verbal fluency tasks, we measured retrieval in line with the structural organisation of the mental lexicon and additionally, a more controlled search through the mental lexicon.

Results
Semantic retrieval assessed in grade 5 accounted for variance in reading comprehension in grade 6, in addition to variance accounted for by vocabulary size and reading comprehension in grade 5.

Conclusions
The ability to search through the mental lexicon, along the lines of its hierarchical structure, is important for children's reading comprehension development in the upper primary grades.