Processing trimorphemic words: linearity and internal structure

The internal structure of trimorphemic words and its potential impact on stem access have not as yet been explored in great depth. The combinatory possibilities of a single stem with two affixes can vary between left-branching unkindness or right-branching unhelpful. The non-linearity of the grouping leads to an obvious query regarding the decomposition of the complex words and the consequences this may have for lexical access of the stems. To address this question, we conducted a cross-modal priming experiment employing a combination of trimorphemic primes and stem targets across four conditions: semantic (indecisive - hesitate), form (extensive - tense), morphological left-branching (e.g. un-kind-ness > kind), and right-branching (e.g. un-help-ful > help). Behavioural results revealed facilitation in both left- and right-branching conditions, whereas no such effect was found in semantic and form conditions. The ERP analysis, however, revealed different patterns between the semantic and morphological conditions. Semantically related primes facilitated the targets, evidenced by an N400 attenuation. The two morphological conditions differed; facilitation effect was not detected in the morphological left-branching condition, whereas right-branching related primes inhibited access to the target, indicated by an increased N400 response compared to control primes. This asymmetry between the two morphological conditions suggests a difference in the speed and ease of lexical access in trimorphemic words which is affected by their internal structure with suffixes being less easily separable from the stem than prefixes.