Flexibility is probably the most important control function. An individual must be able to quickly switch from one plan to another, because often in life something else happens that requires our attention and requires us to change the intended plans. John Lennon wrote it: "Life is what happens to you while you make other plans." You need flexibility when you gain new knowledge and, by extension, new skills. When learning new skills, you constantly use feedback on your own behavior. You hear what was good and what was not good and you adjust your actions accordingly. Somatic labeling and pattern formation play a very important role. Young children still have a lot of difficulty changing lines. During a study, three year olds were given the task of sorting cards with different pictures. Flower pictures with flowers, car pictures with cars, etc. They are good at this. Now some cards are red and others are blue. When the sorting rule changed during the research to red by red and blue by blue cards, the children appeared to understand the rule, but not be able to implement it. They continued to sort by picture. However, children quickly get better at this, but full flexibility is not fully developed until around the age of fifteen. Two brain areas in the frontal cortex are important when adults learn from feedback about their own behavior. Namely: the upper part of the lateral frontal cortex and an area in the middle of the frontal cortex. The lateral prefrontal cortex is important for working memory. This part of the cortex is active when remembering language, the word five. But it is also active when remembering pictures, for example an image of the number 5. And finally, it is active when remembering the number five as an arithmetic unit. The other area in the middle of the frontal cortex mainly has an alarm function. It becomes active when people make mistakes. These areas, which are important for goal-directed behavior, are still developing in young people until late adolescence. It is therefore difficult for adolescents to complete a task in a new way. If they are used to doing a certain task in a certain way, it is difficult to change them. It gives them guidance to use the old method. They cannot yet switch flexibly between different tasks. They therefore remain stuck in the old approach.