wrote on Jan 8^th, 2015 at 7:02pm:

but a 20-something polygrapher, w/ no more training than a barber

I really don't think age has much to do with it. But, your "barber" analogy is fitting. Both trades require a couple months of training. But, does a barber get better over the years? Does his skill improve with a thousand or more haircuts? The answer is probably not much as after a hundred or so, he's reached the threshold of the asymptote. I see often on polygraphers' websites how they boast of having done 10,000 or more polygraphs, but most likely their skills were already honed after the first hundred or so.