Bob, yes, it is good for the brain. The detail work, what ever the level, the concentration, all good stuff. I know all of this without viewing the link.
But frankly speaking, despite possibly pushing the political envelope; Screw AARP. Whatever good they may do as an organization is countered by their leanings. In the grand scale, they actually treat us 'retired people' as simple-minded, second class citizens; unable to make our own intelligent decisions. And the discounts they offer, are generally available through many different sources. AARP is doing you no great service.
Sorry.