1. What was the main question in your dissertation?
Do people listen less well to what someone is saying, if they have started preparing their own response, while still listening? If this is the case, would it help if what the other is saying is predictable? 
Most people find having a conversation easy despite the fact that they need to multitask to do it; to alternate between the role of the listener and the speaker. We know that people can be surprisingly fast in switching from listener- to speaker-role during a conversation. When the first person stops talking, the other person starts their response within about 200 milliseconds. However, when we are not in a conversation, preparing speech takes about 600 milliseconds when naming an object in a picture, or 1000 milliseconds when preparing a sentence. How, then, arepeople so quick at taking over the speaker-role after their conversation partner stopped talking? We now know that people already start preparing their response, while still listening to the other person. This means that people are doing two things at the same time: listening and comprehending the speech of the other and planning their response. Usually, when we try to do two things at once, we find it difficult, because we have to divide our attention and thinking capacity. Thus, we might expect listening performance to suffer when we are preparing our response. I investigated whether this is the case.
3. Why is it important to answer this question?
Conversation is the main means of human communication and often comes across as easy and effortless. Yet our brains are limited in the number of tasks they can do smoothly at the same time, and it is possible that this influences our speaking and listening behavior and performance. In order to avoid long pauses during conversations, people might be forced to listen less well to the other while planning their response. This is important to investigate, because it tells us how humans are able to converse so easily and smoothly, how they understand and plan speech, but also helps us explain what can go wrong – why conversations are sometimes misinterpreted and misremembered.
4. Can you tell us about one particular project?
In one study, I asked whether people process the meaning of what they hear thoroughly, if they are preparing their verbal response at the same time. Participants heard sentences that ended in an expected way (“With tea we always eat a cookie”) or an unexpected, even implausible way (“With tea we always eat a mouse”). Half of the time, participants also named a picture that appeared on screen together with the sentence’s final word. I used electroencephalography (EEG) to see the difference in the brain’s response while planning speech and hearing an expected or unexpected sentence. Normally, if people hear an unexpected ending of a sentence, there is a peak in their brain activity at the end of the sentence (the N400). This is a surprise response, as if they were thinking “Huh? This did not go as I expected”. So we looked whether we found this peak when participants were preparing speech and heard the unexpected sentence. In my study, people did not show this peak when preparing their response at the same time as listening to unexpected sentences. We did find this peak when participants did not have to prepare a response. This finding demonstrates that when people are preparing their response while listening, heard speech is often not processed to the same depth for meaning, as when just listening.
5. What was your most interesting/ important finding?
A key finding of this thesis is that people listen less well when preparing their response while still listening. Interestingly, when I asked people to actively share their attention between preparing their response and listening, and try to listen more carefully, people’s listening performance improved. However, this had a cost. People found it more difficult to prepare their responses when they were instructed to listen more carefully: they made more mistakes naming the pictures.
6. What are the consequences/ implications of this finding? How does this push science or society forward?
It is very important to examine the demands of attention and thinking capacity when preparing a response while still listening, because it helps us understand which parts of a conversation are very demanding. This is not only the case for normal hearing individuals, but perhaps also in particular for people with hearing impairments, who often find it exceptionally difficult to hold a conversation. Pinpointing which processes are so demanding during a conversation could facilitate interventions to teach people strategies to reduce these demands. It is also important for our understanding of how the brain works during conversation: it is intriguing to look at how comprehension and production work together, since for a long time, these two processes were studied in isolation.
7. What do you want to do next?
My wish is to continue investigating not only which processes are so demanding when preparing speech while still listening, but also why this is the case. Why does speech preparation make you a worse listener? Are there other ways to capture the impact of speech preparation on listening? Do people, for example, more easily disregard the speech errors of the person they are listening to if they are preparing their response at the same time? Do people remember the gist and events of a conversation less well, if they are preparing their response while listening? Which aspects of conversation would increase effort during listening? How does the predictability of the conversation influence this? These and related questions I would like to address, not only in the normal hearing population, but also in hearing-impaired individuals.
Read more
– Link to dissertation
Interviewer: Merel Wolf
Editor: Julia Egger
Dutch translation: Lynn Eekhof
German translation: Bianca Thomsen
Final editing: Merel Wolf
