Individual Differences in Sensitivity to Morphological Structure in Words and Nonwords

Understanding visual word recognition has been a central goal of psycholinguistics from its early beginnings. Examination of the statistical properties of language has uncovered many aspects of words that facilitate recognition. In addition, evidence from both behavior and computational modeling suggests that individual differences in experience and the strength of connections in an individual’s reading network affect the sensitivity to these statistical properties in language. Morphology has special properties in this sense as morphologically related items have statistical regularities across both form and meaning. The current study examined whether individual differences in skill modulate sensitivity to morphological structure. Specifically, we looked at the relationship of three established measures of sensitivity to morphological structure. We used a visual lexical decision task to simultaneously examine sensitivity to morphological structure in nonwords and words. Linear mixed effects modeling was used to assess the main effects of each measure and to extract individual effect slopes to be used in individual differences analysis. Participants also completed an individual skill battery meant to examine language ability. We found that the morphological effects showed systematic variability. As skill increased the nonword complexity effect increased and the morphological effects in words decreased. In addition, the nonword complexity effect in reaction time and the family size effect seem to be indexing opposite ends of the same dimension of variability. Base frequency, while closely related to family size, indexes a separate dimension of variability. Implications for the characterization of each of the effects and possible future directions are discussed