Timing is key: Morphological structure affects early and late stages of typed word production

There is longstanding evidence of an involvement of morphology in typing, but it is currently inconclusive as to where and how effects arise Some results suggest that morphological processing occurs at early stages of production, prior to the initiation of motor execution, whereas others report late effects. Still other findings indicate that units other than morphemes may dominate processing during typing. The present study probes existing results by investigating effects of morphological structure on both early and late measures during typed word production. Our experimental design avoids coinciding syllable and morpheme-boundaries and reduces confounding factors of constituent frequency by focusing on one suffix and four target transitions. We tested 301 native speakers of English in an online single word typing task, using a two-tier decision and recall paradigm. To pinpoint potential effects, we measured writing onset times (WOT) as well as inter-key intervals (IKIs) throughout production. We find an effect of morphological complexity on both early (WOT) and late measures (IKIs). Crucially, the effects are modulated by individual typing speed, with fast typers showing a greater slowdown during the execution of keys at the morpheme boundary. Additionally, we find a trade-off between preparation and execution so that, overall, more delayed mean writing onset leads to faster execution at boundary-straddling keys. Lastly, word length interacts with effect size, with syllable effects only emerging in longer words. Our results contribute to recent discussions of the language production system as adaptive and flexible, able to accommodate varying task demands with varying processing strategies.

Manuscript under review