Final Report Summary - O-CODE (Cracking the orthographic code)
Learning to read is thought to involve adaptation of basic object recognition processes to the very specific characteristics of printed words. Our research has pointed to one key adaptation thought to involve a modification in the receptive field structure of location-specific letter detectors. Our research on crowding in letters and other kinds of stimuli suggests that the crowding zone is reduced for letter stimuli in order to optimize the parallel processing of letters in words. Our research on letter-in-string identification also suggests that receptive fields (that determine the crowding zone) are biased to the left for letters falling in the left visual field (for languages read from left-to-right) in order to give priority to the initial letters of words. A systematic comparison of the way we process strings of letters (typically random consonants – FHTRM) compared with other types of stimuli such as symbols (#%?@§), digits (72498), and simple shapes (e.g. star, cross, heart, etc.) – has helped identify the nature of the processing that is specific to strings of letters, and the nature of the adaptive mechanisms that are one key to the development of skilled reading behaviour. Furthermore, our investigation of orthographic processing in non-human primates (baboons) has helped bridge the link between general object processing mechanisms and the adaptation of these mechanisms to the specificities of letter string processing.
Our developmental research has allowed us to specify the developmental trajectories associated with the different types of orthographic code postulated in our theoretical framework. We have shown that the development of flexible sublexical orthographic representations is tightly related to the development of skilled reading behavior, as measured by standardized reading tests. On the other hand, our results point to a transition from two types of precise letter position coding during reading development – one type of coding involved in the slow process of phonological recoding used by beginning readers, and a more automatized process of grapheme-phoneme conversion used by more skilled readers. Finally, we have shown that the well-established initial letter advantage found in skilled readers gradually emerges during primary school education, hence supporting our hypothesis that this advantage is driven by adaptive mechanisms rather than serial processing.