Evidence for Morpheme Transposition Effects in Developing Readers

Purpose: Skilled readers are sensitive to morpheme position within complex words, recognizing stems freely (e.g., book in bookmark or textbook) compared to the relatively position-dependent processing of affixes (e.g., the suffix –er conveys meaning at the end of reader but not at the onset of error; the prefix re– conveys meaning at the onset of replay but not at the end of there). The present study examined for the first time when these distinct positional encoding mechanisms develop in children. Method: A sample of 204 Australian primary school children ranging from 7 to 12 years of age (M age = 9.94 years, SD = 1.41; 113 female) completed three lexical decision tasks to compare morpheme transposition effects relative to controls between stems and suffixes (Experiment 1; almagic vs endweek), stems and prefixes (Experiment 2; takemis vs markbook), and semantically opaque and transparent stems (Experiment 3; bowrain vs ballfoot). Results: In Experiments 1 & 2, replicating findings with skilled readers, linear mixed effects models revealed a significant effect of transposition in ERs and RTs for compound conditions but not affix conditions. Experiment 3 found a significant effect of transposition in ERs and RTs for transparent conditions but not opaque conditions. These morpheme transposition effects were further analysed for effects of age and reading fluency.Conclusion: These findings chart the developmental trajectory of morpheme transposition effects, reflecting the early establishment of distinct positional encoding constraints on English stems and affixes that solidify over time with accumulated exposure to morphological regularities in text.