L’objectif de la présente recherche est de déterminer dans quelle mesure l’effet de fréquence du voisinage orthographique dans une tâche de catégorisation de couleur de mots est modifié lors du vieillissement lorsque la vitesse de traitement des participants est prise en compte. Deux conditions de mots colorés ont été comparées dans une tâche de catégorisation de couleurs réalisée par un groupe d’adultes jeunes (M_âge=21,62) et un groupe d’adultes âgés (M_âge=66,04). La moitié des mots ne possédaient pas de voisin orthographique (ex., pistil), l’autre moitié avaient un voisin plus fréquent (ex., tirade/tirage). Les résultats ont montré que l’effet de fréquence du voisinage sur les temps de catégorisation de couleur variait différemment dans chaque groupe d’âge selon la vitesse de traitement. Ces données sont discutées dans le cadre des théories du vieillissement cognitif et de la reconnaissance des mots écrits.

The objective of this research was to determine to what extent the effect of higher-frequency orthographic neighbourhood in a word colour-categorization task is changed during aging when processing speed is taken into account. In addition, the effect of the lexicality of the stimuli on colour categorization was examined, as well as its variation according to age and processing speed. Fifty-two young adults (M_age=21.62) and 52 older adults (M_age=66.04) participated in this study. For each age group, two sub-groups were created according to the processing speed of the participants as measured by the WAIS Coding subtest. Two conditions of words (written in red, yellow, green or blue) were presented in a colour-categorization task. Half of the words did not have any orthographic neighbours (e.g., pistil [pistil]), while the other half had a higher-frequency neighbour (e.g., tirade [tirade]/TIRAGE [draw]). A control condition with a series of Xs was added to test the influence of the effect of the lexicality of words on the colour-categorization times. As a whole, the results showed slower colour-categorization times for words compared to a series of Xs, which did not vary with age and processing speed. Importantly, the results showed that orthographic neighbourhood frequency interacted with age and processing speed, on colour categorization response times. More precisely, the neighbourhood frequency effect was found to vary differently according to processing speed in each age group. For the fastest young adults, the facilitatory effect of higher-frequency orthographic neighbourhood was obtained, whereas no such effect was found for the slowest young adults. The fastest older adults did not exhibit any effect of higher-frequency orthographic neighbourhood whereas a facilitatory effect was observed for the slowest older adults. Therefore, these data suggest that both aging and the processing speed of the participants influence the interference effect of reading on colour categorization. These findings are discussed in the context of cognitive aging theories and models of written word recognition.