>> tens of millions of people do it, but does it work? here is abc's linsey davis. >> reporter: imagine if a game that starts off so easily that it likes like child's play, it could actually make adults smarter. when 66-year-old susan brandt saw her parents starting to lose their memory, she turned to online game called lumosity, in an attempt to keep up her own mind. >> my biggest thing is not getting cancer, it is losing my mind. >> reporter: when she started forgetting people's names, this is the game susan turned to. familiar faces. on my right is maria, jennifer and that's james. try to remember those names. we will come back to them later. lumosity with 60 million users is the most popular of several online brain training programs created by neuroscientists.