Figure 5.

Performance on pair BC after training on a four-item list (left panel) and BD after training on a five-item list (right panel). Two animals each were trained on the BC+, BC−, BD+, and BD− conditions, where the “+” indicated that a reward could be obtained by responding to the items in the order in which they appeared in the original sequence (B→C or B→D), and the “−” indicated that a reward could be obtained by responding to the items in the order opposite to what they appeared in the original sequence (C→B or D→B). If the birds learned nothing about the order of the internal items, then when presented with these pairs they ought to take as long to learn the positive pair condition as the negative pair condition. Rather, it is clear that the birds tested with the positive pairs fared far better than those tested with the negative pairs.