In “Lasting effects of phonics instruction” on the Teaching Effectively! blog, JohnL quotes what appears to be the abstract of a study:
Thompson, G. B., Connelly, Vincent, Fletcher-Flinn, C. M. & Hodson, S. J. (2009). The nature of skilled adult reading varies with type of instruction in childhood. Memory & Cognition, 37, 223-234.
Does the type of reading instruction experienced during the initial years at school have any continuing effect on the ways in which adults read words? The question has arisen in current discussions about computational models of mature word-reading processes. We tested predicted continuing effects by comparing matched samples of skilled adult readers of English who had received explicit phonics instruction in childhood and those who had not. In responding to nonwords that can receive alternative legitimate pronunciations, those adults having childhood phonics instruction used more regular grapheme-phoneme correspondences that were context free and used fewer vocabulary-based contextually dependent correspondences than did adults who had no phonics instruction. These differences in regularization of naming responses also extended to some low-frequency words. This apparent cognitive footprint of childhood phonics instruction is a phenomenon requiring consideration when researchers attempt to model adult word reading and when they select participants to test the models.
I have not looked into the study so I don’t know anything about its methods and validity, but it sounds interesting and worth looking into.