Then it stops working, and there is only one lever

Children habituate to noise the way everybody does. The volume that stopped a four year old does not stop the same child at six.

At that point there is exactly one lever available, which is more. Louder, or longer, or a harder edge to it. That is the escalator, and nobody steps onto it on purpose. You step onto it because the old level stopped producing the result, and the only adjustment the method allows is upwards.

This is worth knowing for one practical reason. If shouting is your main tool, the amount of it required goes up every year. Not because your child is getting worse. Because the tool wears out.

None of that is a new observation. al-Ghazali states it as a claim about what repetition does, seven hundred years before anybody filmed a family. Our copy of the Ihya' holds it at section 26814, in Arabic only, and this is the sentence exactly as stored:

ولا تكثر القول عليه بالعتاب في كل حين فإنه يهون عليه سماع الملامة وركوب القبائح ويسقط وقع الكلام من قلبه

Our rendering, and it is a rendering rather than a translation of record: do not multiply reproach upon him at every moment, for that makes it easy for him to hear blame and to commit ugly things, and it drops the impact of speech from his heart.

The last clause is this step in his words. The clause before it is worse news than this step gave you, and it is worth having. The effect is not only that the blame stops working. It is that the child gets easier with blame, and easier with the conduct the blame was aimed at.

He gives the practical form of the rule in the same section: وليكن الأب حافظا هيبة الكلام معه فلا يوبخه إلا أحيانا. Let the father keep the weight of his speech with him, and not rebuke him except occasionally.