Evaluating the feasibility of using heart rate to measure auditory attention allocation during spoken language processing

A deceleration in heart rate (HR), along with a lengthening of the time between heartbeats, has been associated with attentional engagement. Here, we investigated the feasibility of using changes in HR to estimate attentional engagement during spoken language processing. Prior neuroimaging studies suggest that speech processing of an unknown language is more cognitively demanding; we thus designed an experiment to test this finding through HR. In an active listening task, we measured cardiac responses in 66 native English speakers (34 monolingual, 32 simultaneous bilingual), who listened to spoken passages in two conditions: one in a familiar language and the other unfamiliar. Results demonstrated significant condition effects on participants' BPM (beats per minute) and IBI (interbeat interval). Listening to an unfamiliar language induced significantly lower BPM and a trend of longer IBI, particularly during the first five out of nine trials. Our finding aligns with previous neuroimaging evidence that processing an unfamiliar language demands more attention than a familiar one. Our analysis also revealed that the effects were independent of participants' bilingual experience or language and cognitive abilities. Overall, our results indicate that HR measurement has a potential in psycholinguistic and cognitive research.