I am not sure about the degree of effectiveness for a 4 yr old.
But this is what I did with my teenagers (4 of them) and it worked great with them.
Rules --argue about them is not an option. You may state your opinion in 2 sentences or so. You may state the reasons for your opinion in about 2 sentences. But that should all take you about 5 minutes. AFter that my ears are closed so no use talking.
I will consider your words because you may have some valid points.
I will give you my opinion and reasons in the same length of time and words--so we don't get sick of each other. ; )
Then all discussion is closed. If I have decided to change the rule after thinking about it for a few hours, I will let you know. But you dont' ask me, you don't bring it up again, and you don't throw any fits of any kind.
This teaches them how to talk about things, how to be patient, how to present their case, and makes a peaceful household.
If they cannot close their mouth after the alloted time they are told to go to their room. (had one like that) In the bedroom they can talk all they want, but there is no one to discuss it with and mine was very social. He hated to sit there arguing with a blank wall. LOL He would rather get it under control and learn how to be with the family and enjoy our time together rather than arguing.
But in order for this to work you have to let them have their time of thoughts without interruption. And they have to learn to hear you speak without interruption. Questions are allowed but only a few....nothing to drag out things.
Good luck