Ordinal position in the serial learning of rats

Rats were runway trained on each of two, three-trial series consisting of d ifferent varieties of reward (X, Y, and Z) and nonreward (N) serving as tri al outcomes. The two series are represented as XNY and ZNN. Distinguishing the two series were different brightness and texture cues on the runway flo or. Transfer tests, conducted after the rats had developed faster running f or rewarded trials than for non-rewarded trials and slower running on Trial 2 of ZNN than on Trial 2 of XNY, provided evidence that trial position, ra ther than item memories, was controlling the discriminations. Ln Experiment I, reversing the floor cues completely reversed the discriminations. In Ex periment 2, transfer to NNN did not change the routine patterns of approach that had been established.