Capturing the Attentional Trade-off between Speech Planning and Comprehension

In conversation, future speakers often plan speech simultaneously with comprehension, which means that they must divide attentional resources between these processes. In this EEG study, we used responses to linguistic attention probes (i.e., syllable "BA" presented during spoken sentences) to track temporal variations in attention to comprehension. Participants were asked to listen to prerecorded sentences with expected or unexpected sentence-final words. Each sentence was presented twice, once with and once without the attention probe starting 100 msec after the target word onset. Participants saw a picture 50 msec before the target word. Depending on the test block (picture naming or button press), participants either named the picture or pressed the space bar, both after an 850-msec delay. The probes elicited a negative potential approximately 100 msec after probe onset (i.e., an attention probe effect) in all probe conditions. Unexpectedly, neither word expectancy nor speech planning influenced the timing or strength of the attention probe effect. This indicates that expectancy of words in Dutch does not affect the allocation of attention toward these words 100 msec after their onset (i.e., the time of the probe presentation). Interestingly, engaging in speech planning does not seem to divert attentional resources away from comprehension at the moment of probe presentation. These findings imply that listeners are able to effectively distribute their attentional resources between comprehension and speech planning and carry out these processes at the same time. Considering these unexpected findings, using attention probes might not be the best approach to capture variations in temporal attention in dual-task paradigms.