Morpheme Transposition Effects in Developing Readers

Purpose Skilled readers are sensitive to morpheme position within complex words, recognizing stems freely (e.g., book in bookworm or textbook) compared to the relatively position-dependent processing of affixes (e.g., the suffix –er conveys meaning in reader but not error). The present study examined when these distinct constraints may emerge in reading development.Method Australian children aged 7-12 years (N = 204; M age = 9.9; SD = 1.4; 113 girls) completed three lexical decision tasks to compare morpheme transposition effects relative to controls between stems and suffixes (Experiment 1: endweek vs almagic), stems and prefixes (Experiment 2: markbook vs takemis), and semantically transparent and opaque compounds (Experiment 3: ballfoot vs bowrain).Results Experiments 1 and 2 replicated findings from skilled readers, where LME 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 semantically transparent conditions but not opaque conditions.Conclusion These findings reveal the early establishment of distinct positional encoding mechanisms for English stems and affixes in developing readers. Patterns in morpheme transposition effects, modulated by semantic transparency, appear to quickly solidify with time and accumulated exposure to morphological regularities in text.