Figure 1.

A schematic of the two test phases. In Phase 1, food items were hidden under each array (a). Each cup was then lifted, in succession, as shown in (b) and (c) for the first two cups, and this continued for all cups. Then, some cups were lifted a second time, and sometimes those again had a food item underneath (d), but sometimes did not (e). In Phase 2, cups again were baited (f), and all cups were lifted in succession (g, h). Then, two pairs of cups in one of the arrays were transposed in position (i). After these transpositions, food items that already had been seen were now in new positions (j). All cups in that array were then lifted again in succession.