I'm not looking for a certain word, but rather a concept or a stage of childhood development.
Specifically, I'm wondering about that stage when children who are doing something they know they're not supposed to be doing attempt to conceal their activities. This usually results in them giving themselves away by being unusually silent.
This stage seems to require children being developed enough to know what's allowed versus disallowed and knowing they can conceal things from their parents (or attempt to).
What is this stage of early childhood development, or what are the different aspects of development that are required for this behavior?