PaulB,
Greetings... While Lt. Columbo may have sited only one TV program, there are several studies/articles out there that support the idea that there is a "learning window" for language and it is from age birth to approx. age 10.
Newsweek Magazine, from February 19, 1996, with the cover being "Your Child's Brain" discussed this issue stating that, "A child taught a second language after the age of 10 or so is unlikely ever to speak it like a native."
http://www.gymboreeturkey.com/pdf/yo...n_newsweek.pdf
In the Februrary 3, 1997, issue of Time Magazine, cover article, FERTILE MINDS, stated "The ability to learn a second language is highest between birth and the age of six, then undergoes a steady and inexorable decline. Many adults still manage to learn new languages, but usually only after great struggle."
http://www.time.com/time/magazine/ar...5854-9,00.html
Here is another article from the University of Maine http://www.umext.maine.edu/onlinepubs/htmpubs/4356.htm
And here is a special report from the National Science Foudation
http://www.nsf.gov/news/special_repo...tics/learn.jsp
I wish you good luck with your language endeavors.