There are three relevant areas of developmental psychology that directly apply to justifying the argument that young children should not be held responsible for criminal actions:
- Piaget's Theory of Cognitive Development
- Kohlberg's Theory of Moral Development
- Baumrind's Classification of Parenting Styles
Jean Piaget outlines in his theory of cognitive development four primary stages of cognitive development that children go through. In the first two stages, which span the years of development between birth and age 7, Piaget theorizes that children will develop various characteristics such as egocentrism, transductive reasoning, cause-effect relationships, irreversibility, conservation, and other important pre-operational attributes but will not at this point have developed the ability to use logic to solve problems. Concrete logical operations will be developed after age 7 so prior to this, children are not thinking about criminal acts in a logical manner as adults would thus rendering them incapable of making appropriate decisions and being culpable for their actions.
Lawrence Kohlberg outlines in his theory of moral development three stages, with six substages, of moral development for making decisions. In the first stage, the pre-conventional stage, children's moral associations are based only on the concepts of punishments and rewards. In other words: "Will my actions get me a cookie or a spanking?" This stage begins with the cognitive functioning after birth and can extend up into the early teens. Because there's no guarantee that the children were taught correct moral associations by the adults and peers around them and they are essentially programmed to act in their own self-interest, it is justified that they not be held accountable for criminal actions until after this stage has passed and they have reached stage two, which is obedience to authority and the rules of society and the understanding of consequences.
Finally, Diana Baumrind posited that there is a large correlation between the parenting styles in which a child is raised and their ability to make sound, rational, and morally affirmative decisions. Children who are raised in an atmosphere in which criminal activities are made out to be morally correct will be much more likely to commit their own criminal actions. The legal system is likewise justified in not ruling that the children are responsible for these criminal actions as children, by nature, will learn to replicate and reenact the actions they see in their parents and peer of authority.