Diagram of the delayed match to sample radial water maze task, including sample (left) and test (right) trials. S = start (location changes), G = goal (location remains fixed). Each day rats were given one forced-choice sample-trial, with access to all but the start (S1) and goal (G) arm blocked. The goal arm contained a submerged platform. On the test trial (one hour later), all arms were open and a different start (S2) arm was used, to test memory for the spatial location of the current goal location. Only one sample and one test trial were given each day. The sequences of start arms and goal locations used each day varied systematically among forty-eight patterns that regulated the sequence of start and goal arms, the turn angles, and the relationship between the start and goal arms across trials. Exemplars for the first and second day of testing are provided (actual testing continued for 60 days).