When participants read a text for comprehension while identifying a target letter, the letter is more often missed in a frequent function word than in a less frequent content word. This is the missing-letter effect. Studies have shown the importance of both frequency and word function. The role of each of these factors in development is less understood. The goal of this study was to revisit the influence of frequency and word function in the missing-letter effect in development with better-controlled stimuli. Two hundred sixteen participants took part in this study and were divided into five groups (6-7 years, 8 years, 9 years, 10-11 years, and university students). They were asked to read four experimental texts for comprehension and to circle a target letter. The results showed a basic missing-letter effect with more omissions for a frequent function word than a less frequent content word for every group. When frequency was controlled, we found a word function effect as early as 6-7 years of age, with more omissions for a function word than a content word. In contrast, when word function was controlled, an effect of frequency was only significant for adults and 8-year-olds. These results clarify discrepancies in the literature and support the importance of rigorous stimuli control.
Keywords: development; frequency; letter detection; missing-letter effect; reading; word function.