Age-related differences in speed of processing: unconfounding age and experience

This study was designed to explore age constraints on speed of processing on a lexical decision task. In order to unconfound age and experience, the participants were presented with two lexical decision tasks, one in German (the native language) and one in English (the second language), as well as a symbol matching task. Three groups of subjects were formed: (1) 16-year-olds who had received formal instruction in English for 5 years, (2) 16-year-olds who had received only 1 year of instruction in English, and (3) 14-year-olds who had received 3 years of instruction in English. Inclusion of these three groups permitted the study of the effects of language experience in the absence of the usual age-experience confound. When the lexical decision task involved German words and nonwords, the older children responded more quickly than the younger subjects. However, when the stimulus items were English words and non-words, this age-related progression was disrupted and response speed was related to experience with English as a second language. These results suggest that experience is an important factor to consider when trying to account for lexical access times. Implications for understanding age-related differences are discussed.