Chasing psycholinguistic effects a cautionary tale

Many studies have addressed the issue of whether age of acquisition and/ or frequency affect particular lexical tasks. Methods typically employed in such studies are based on the general linear model (e.g., ANOVA or multiple regression). These methods assume manipulated independent variables whereas the usual approach of investigating age-of-acquisition and frequency effects uses estimated norms of word properties. This failure to truly manipulate variables violate the assumptions of the analyses. A simulation is provided that demonstrates how this violation can lead to erroneous conclusions of effects when none are present. Recommendations are made for a more correlational approach to analysis using structural equation modelling techniques. It is also discussed how this use of estimates of lexical data is problematic for determining effects throughout psycholinguistic research. {\textcopyright} 2006 Psychology Press Ltd.