The typical gap between speech turns in conversation is just 200ms. The small gap is possible because we construct our response while the other person is speaking.
When we talk we take turns, where the “right” to speak flips back and forth between partners. This conversational pitter-patter is so familiar and seemingly unremarkable that we rarely remark on it. But consider the timing: On average, each turn lasts for around 2 seconds, and the typical gap between them is just 200 milliseconds—barely enough time to utter a syllable. That figure is nigh-universal. It exists across cultures, with only slight variations. It’s even there in sign-language conversations.
“It’s the minimum human response time to anything,“ says Stephen Levinson from the Max Planck Institute for Psycholinguistics. It’s the time that runners take to respond to a starting pistol—and that’s just a simple signal. If you gave them a two-way choice—say, run on green but stay on red—they’d take longer to pick the right response. Conversations have a far greater number of possible responses, which ought to saddle us with lengthy gaps between turns. Those don’t exist because we build our responses during our partner’s turn. We listen to their words while simultaneously crafting our own, so that when our opportunity comes, we seize it as quickly as it’s physically possible to. (Source)
Implications here for interface design. Think about related issues — Calm Tech, etc.