True, correlation does not prove causation. However, there is much evidence that the prefrontal cortex deals directly with the ability to make sound judgments, especially in studies of people with prefrontal cortex damage (as in this paper.)
If you are looking for a more scholarly paper on the subject, let me point you to this article by Ken C. Winters, Ph.D. of the University of Minnesota Department of Psychiatry. The article focuses on adolescent risks of drug abuse, but mentions the youth/judgement correlation.
If you're really interested in the subject, check out http://scholar.google.com.