Somehow this became a science question. I was asking a Christian question. The science I can read. The Christian angle isn't included in the reading.
The Christian in me says to go by observation rather than science. Time and again we have seen children step up and do the honorable things. An average intelligence child should be accountable by at least 12 years old. Mind you, there is still foolishness in their minds but they can control it by then. Unless they are spoiled rotten and not taught to be honorable. We see that too.