When we talk to one another, we take turns. This simple rule seems to apply to all human conversation, whether the speakers are English city-dwellers or Namibian hunter-gatherers.
One person speaks at a time and, barring the occasional interruption, we wait for our partner to finish before grabbing the conch. Timing is everything: cutting someone off is rude; leaving pregnant pauses is awkward. You need to leave a Goldilocks gap—something just right.