I wrote:

The discussion of Twenty Questions reminded me of a game I learned from Alan Frank (who I believe also invented it), called "Plenty Questions". In this game, all queries must take the form "Is it more like X or Y?" In the warm-up version of the game, that's the only constraint. But in the real version of the game, there's a further catch: each question must re-use the better of the two matches from the previous question. That is, if the answer to "Is it more like X or Y?" is "X", then the next question must be of the form "Is it more like X or Z?", whereas if the answer to "Is it more like X or Y?" is "Y", then the next question must be of the form "Is it more like Y or Z?".

Andy Latto tells me that the game I called "Plenty Questions" is not original with Alan Frank; in fact, Alan learned it from Andy, who learned it from Diana Steifbold. That's as far back as I've been able to trace things with any measure of certainty. Jim Propp