May be interesting, on this matter, to know what Romans, fathers of the western civilization, thought about it. Well, the capability to behave, in accordance with the principle of ius civilian, was recognized to the pubescent, if female, at 12 years old, if male, using the criterion of determinate case by case based on the scrutiny of physical characters (habitus corporis) related to the procreation capability. It was recognized entirely to males, not entirely if female.
It was completely refused to the Infantes, children not able of a reasonable speech (qui fari non possunt), from classic advanced age the trend was to coincide the end of the infantia with the accomplishment of the seventh year.
Was recognized partially to the impubescent infantia maiores (impubescents that had overcome the infantia). They were admitted to do, lawful and without assistance, those legal affaires that involved acquisition of a privilege and those actions advantageous to their self, was enough that they were able to understand the sense of the verba to pronounce.