Is switching more costly in cued than voluntary language switching? Evidence from behaviour and electrophysiology

Multilingual language control is commonly investigated using picture-naming paradigms with explicit instructions when to switch between languages. In daily life, language switching also occurs without external cues. Cued language-switching tasks usually show a switch cost (i.e., slower responses on switch than non-switch trials). Findings of switch costs in response times are mixed for voluntary language switching. This pre-registered study uses a bilingual picture-naming paradigm to compare voluntary and cued language switching in 25 highly proficient Dutch-English bilinguals using EEG. We analysed the N2 ERP component and midfrontal theta oscillations, two common electrophysiological markers of cognitive control in task and language switching. We observed significantly smaller behavioural switch costs in the voluntary task. This suggests that voluntary language switching is less effortful than switching based on external cues. However, we found no electrophysiological switch effects in either task. We discuss factors which may contribute to the inconsistency between behavioural and electrophysiological findings.