The Estivill method to re-educate sleep habits is a method that, as Dolores mentions, continues to cause many controversies. It is based on behavioral psychology, but it is not only the only technique that exists within this theory.
I bought the book determined to apply it, but I had no heart, I didn't even try to do it and until recently my son needed me to lie next to him to fall asleep.
I applied what is known as "Chip economy", also a behavioral psychology technique. It consists of reinforcing by means of a card (points, stars, smiling faces, stickers), the behavior that we want, in our case that the child goes to bed alone.
We made a calendar with the days of the week and every time he went to bed without the presence of mom or dad, he would win a star that we would place on the calendar every morning. If he gathered the stars for fifteen days in a row we would give him a toy he wanted very much. Magic! We made it easier than we thought. At the moment after a story he falls asleep by himself, he has won his toy and the behavior is totally “installed”. Of course, the reinforcement with the cards must be accompanied by hugs, praise, kisses so that once the material reward is withdrawn, the behavior continues to be displayed.
This works for older children, but you also have to keep in mind that many children cannot wait for a long period of time to get the reward, and if they are too young they have not reached the necessary development for the reward to be satisfactory.
It is more or less like the child who gathers cards, in the end he will have a prize. To apply it, you have to be consistent, plan it well and explain to the child what we are going to do by mutual agreement, that he feels part of the strategy.
There is also another technique of behavioral psychology called Desensitization, which is effective in children over three years. Every night instead of lying in bed with the child, the father or mother should sit in a chair next to the bed. Each day move her further and gradually bring her closer to the door until she is out of the room with the door half open. In a few weeks and with constancy the child will have learned to sleep alone. When he succeeds, it is also good to reward him with something he likes very much: a movie trip, a toy etc.
These are behavioral modification techniques, scientifically proven and that give results in most cases if applied to the letter. But remember that each child is unique with different needs and interests and that it is important to evaluate each personal and family situation.
