This post is also available in Dutch.
The speed of questions and responses
How quickly do we respond to each other exactly? Linguists measure this by calculating the number of milliseconds between the end of what the first speaker says (for example, “what do you think of Queen’s music?”), and the start of the second speaker’s response (“Horrible!”).
On average, we respond within 200 to 300 milliseconds, whether we are face-to-face, on the phone, or working together on a project. Of course, there’s some variation as well. Sometimes we already reply while the other is still talking. And other times we can’t really understand the other and respond very late. But generally, we’ll have an answer for everything within a couple hundred milliseconds.
Slow language production
This high speed is extra special if you compare it to the time we need before we can say a single word or a short sentence. We need about 600 milliseconds before saying a word, and for a short sentence our brains need about 1600 milliseconds to prepare.
So, it is impossible for us to sit and listen to someone and only start preparing an answer when they finish talking. We would never be able to respond within 200 milliseconds. We need to prepare our answer while the other person is still talking. But how do you plan your answer when you haven’t heard everything yet?
Your brain as a crystal ball
One possible explanation is that our brain is predicting what the other person is going to say. There is evidence that we predict what type of phrase they are uttering (for example, is it a question or a statement?), what words they might say, and when they might finish talking.
Imagine coming home from work and your roommate starts: “How…”. Your brain will immediately predict a question coming up, with the possible continuation “was work?”. Your brain will then estimate that your roommate needs around 400 milliseconds to utter those words. Based on these predictions, you can start to prepare your answer (“It was fine”), and you can start talking when you expect the other to be done talking. This is a possible explanation as to how we can have quick and smooth conversations despite our slow language production.
Why such a rush?
You might wonder why we need to be so quick, but from a social perspective we certainly need to. Imagine someone asks you to celebrate Sinterklaas together. After 700 ms the odds are larger that you decline the invitation than that you accept. Our brains will also expect that. So, if you’re slow to respond you run the risk that the other interprets your silence the wrong way!
It’s extraordinary how we can respond so quickly during conversation. Once in a while, pay attention when you hear others talk. Doing so will help make the conversation a bit less annoying if you happen to hear it in the silent compartment of the train or in the library. 😉