Photo Credit: Popular Photography http://www.popphoto.com/
If you watch your favourite films, notice whenever a cut takes place; more often than not, it would coincide with the moment when you blink.
Without going too deep into the psychology of it, that split second when you blink allows your brain to process everything your eyes are seeing, and when your eyes open to a new scene, your brain can comprehend that it is now a different time and setting without needing it to be blatantly explained. Consider it your human refresh rate.
This is what allows for the suspension of disbelief when, say, one minute a character is in his room, and in the next shot he’s at the café; your brain internally processes the fact that he picked up his keys, opened and locked the door, and walked down to the café, without needing it to be shown. And this is why you don’t really notice cuts as transitions when they happen in movies.
When editing scenes with dialogue, the most obvious approach is to cut at the point where a character has finished saying what he or she needs to say. But if you cut it right away, it might feel too abrupt, and if you leave too long a pause after the talking has stopped, it might drag on to awkwardness. Try cutting the shot at the moment when the character blinks after he or she has finished speaking. You’d find that your viewer would most likely blink along.