The developmental psychologist Lawrence Kohlberg expanded and refined Piaget's earlier work resulting in the development of his well known stage theory of children's moral development. Kohlberg's moral theory is summarized in our Overview of Child Development, which may make sense to review at this time.
Preconventional Moral Reasoning
According to Kohlberg, children early in their middle childhood stage of development will typically display "Preconventional" moral reasoning. Children displaying preconventional moral reasoning have internalized basic culturally prescribed rules governing right and wrong behavior. For instance, they will appreciate that it is considered immoral to steal from others; that you must earn or be given things and not simply take them. Children will tend to live in accordance with these rules but primarily for selfish reasons, as a way of avoiding punishment and obtaining praise for themselves. At this point in time, they will appreciate their ability to make different kinds of choices, and also the reality of consequences associated with those choices. They realize that morally good behaviors attract praise and positive regard from peers and adults, while morally bad choices bring about unpleasant consequences and negative regard. They act accordingly, in a hedonistic manner so as to maximize their personal pleasant consequences.
Later on in middle childhood, approximately between ages 10 and 12, children begin to show a dawning appreciation of "ideal reciprocity", which is a method for determining what is "fair" based on an appreciation of equality between relationship partners, and a desire to treat others well because ideally, they would similarly want to treat you that well too. People are more familiar with the idea of ideal reciprocity when it is phrased as the "golden rule" (e.g., "Do unto others as you would have done unto you"). Using ideal reciprocity, older children start to make moral decisions based more on how they would like others to treat them if the tables were turned, than based on what they can gain for themselves.
As children think about how rules are negotiated, and how they can benefit other people, they begin to understand and appreciate that there are different types or categories of rules, some of which are more negotiable than others.
Moral rules involve the most basic and socially strict guidelines and societal prohibitions that may never be broken. An example of a moral rule is the basic prohibition against murder and unprovoked assault. It is never okay to harm another person in a physical manner unless in self-defense.
Social Mores or Conventions are moral beliefs that change across social contexts and social groups. These rules are more strictly enforced in some places, and less strictly enforced in others. The idea that it is a sin to disobey one's parents is an example of a social more. In some families, this rule is taken very seriously indeed, while in other families, it is considered to be a guideline at best with many exemptions present.
Finally, Personal Choices involve rules that do not have fixed socially prescribed answers at all, but instead are left up to personal preference. An example of a personal choice might be one family's ritual of having a pizza dinner on Friday nights. At an earlier stage of their development, children might mistake a personal choice for a moral imperative, but by middle childhood, such choices will be recognized for what they are.