Coarticulation across morpheme boundaries: An ultrasound study of past-tense inflection in Scottish English

•We tested whether morphological structure influences systematically coarticulation.•Nine speakers of Scottish English took part in an Ultrasound Tongue Imaging study.•A few speakers idiosyncratically produced morphological effects on articulation.•Morphological effects on articulation were not generalizable across speakers.•The present study informs our understanding of the speech production system.