Consider the problem of collective memory in the context of MOVERS-WORLD. In MOVERS-WORLD, the task is to move furniture and/or boxes from a house into a truck (or vice-versa). MOVERS-WORLD has several agents who can be differentiated by their roles, e.g. hand-truck operators and heavy lifters. There are role-specific operators that the agents can use (e.g. PUSH-HANDTR for hand-truck operators and LIFT for heavy lifters) and there are general purpose operators that any agent can perform (i.e., MOVE, SIGN, and WAIT). The SIGN operator initiates communication between two agents and the WAIT operator is a coordination mechanism; both are discussed in more detail in Section 2.3. Hand-trucks can hold only two boxes at a time. Heavy items require two heavy lifters to carry and bulky items, like a piano, do not fit on hand-trucks. Over time, the agents learn cooperative routines for moving objects around in MOVERS-WORLD.