Morphology and the internal structure of words.

Morphology is the aspect of language concerned with the internal structure of words, and languages vary in the extent to which they rely on morphological structure. Consequently, it is not clear whether morphology is a basic element of a linguistic structure or whether it emerges from systematic regularities between the form and meaning of words. Here, we looked for evidence of morphological structure at a neural systems level by using a visual masked priming paradigm and functional MRI. Form and meaning relations were manipulated in a 2 x 2 design to identify reductions in blood oxygenation level-dependent signal related to shared form (e.g., corner-corn), shared meaning (e.g., idea-notion), and shared morphemes (e.g., boldly-bold, which overlapped in both form and meaning). Relative to unrelated pairs (e.g., ozone-hero), morphologically related items reduced blood oxygenation level-dependent signal in the posterior angular gyrus bilaterally, left occipitotemporal cortex, and left middle temporal gyrus. In the posterior angular gyrus, a neural priming effect was observed for all three priming conditions, possibly reflecting reduced attentional demands rather than overlapping linguistic representations per se. In contrast, the reductions seen in the left occipitotemporal cortex and left middle temporal gyrus corresponded, respectively, to main effects of orthographic and semantic overlap. As neural regions sensitive to morphological structure overlapped almost entirely with regions sensitive to orthographic and semantic relatedness, our results suggest that morphology emerges from the convergence of form and meaning.