Showing the person who is talking is just one part of the formula for editing dialogue effectively. It’s also important to pace the scene naturally. That is, to have just the right space in between each person’s lines.

On one level, this is rather fake. Because, in real conversations, people talk over each other all the time. But in movies and TV, that’s rare. A few directors love overlapping dialogue, but it makes editing so difficult that most films are shot without overlapping lines. That is, Person A talks, and when he finishes, Person B talks. And on it goes. Compare the conversations in any movie or TV show to the conversations around your dinner table. It’s very different.

On film, editors need to find the right pacing for a dialogue sequence. You can speed up a conversation, or slow it down—or try for the pacing that is most natural.