Figure 1.

(a) Example of a single trial in Experiment 1. Observers remembered two serially presented target orientations and reproduced each orientation in a cued order. The second target is reported first in this example, but the order of report varied unpredictably across trials. (b) Four alternative models of the interactions between orientation memories. (c) Predictions of each model for the bias and correlation of the two orientation reports for a small difference in orientation between the two items being remembered. The independent representation models predict no bias or correlation in the memories. The grouping/chunking models predict that any noise in the memory of the group on a given trial will lead to errors in the same direction for both items, producing a positive correlation. The ensemble representation models predict that reports of the two items will be biased toward the mean of the two items and that the two reports will be positively correlated (because any noise in the mean will impact both reports in the same way). The relational representation models predict that nearby orientations will repel each other and that orientations differences near 180° will attract each other.