When I was young, I signed up for Boy Scouts.  At that time--and possibly even now; I'm out of touch with them--a lot of the early skills Taught in Bit Scouts meetings were based on the Kipling book Kim, as well as The Jungle Book.  

One of the most central activities, presented as a game, was Kim's Game.  It just struck me that many of the skills I have been trying to teach, as I taught mathematics, presupposed the skills taught in Kim's Game.

Boy Scouts are probably grinning to themselves, but I need to describe this activity to get everyone on the same page.  (A very close relative of this game is Concentration, so if you feel a sense of deja vu, that's where it's coming from.)

Before the tribes gather, the leader (or, as we called him, the Scoutmaster) lays 30 or 40 assorted objects on a table, and covers them up with a cloth.  Once everyone is present, and preliminary activities have been concluded, each participant is given a sheet of paper, and something to write with   The leader then pulls off the covering cloth, for specific amount of time.  (The more practiced the participants are, the briefer the time interval could be.)

Once the table is covered again, the participants (frenziedly) write down as many of the articles on the table as each one can remember.

At this point, the game can proceed in different ways; each person's list can be verified, to eliminate imaginary articles, and winners announced according to who has the longest list.  Other times, it could be more about which item was most overlooked!  When the troop is divided up into subgroups, such as colors, or clans, the lists of the members of each subgroup could be consolidated (put together), which would make it a rivalry between these subgroups.  (This makes verification less tedious, at any rate.). The whole point is to improve the participants' observation.

I remember we had Kim's Game regularly.  As one who taught Integration, a technique used in calculus, we were using