Figure 1. A computer-controlled probabilistic traveling salesman task enables direct tests of behavioral strategies under uncertainty. A, top, A large, automated arena with a rat shown for scale. Bottom, The temporal structure of a typical trial. B, Rats forage for pellets in highly predictable (left), moderately predictable (center), and actively randomized (right) pellet placements. Placements are shown across all trials (20 d, 3 trials per day). C, The automated system allows for reproducible pellet placement across animals. From the top to bottom of the matrix correlation coefficients are shown for two different predictable distributions and the single unpredictable distribution. D, Pellet distributions from each placement shown in panels B, C have equivalent optimal path lengths. Error bars are standard error of the mean. E, Example histograms are shown for the most predictable (black) and least predictable (gray) distributions that were tested. Vertical colored lines show the mean for the predictable (blue) and unpredictable (red) distributions. The distributions for all animals are plotted as colored circles, with color corresponding to across trial minimum distance. F, RE for each predictability grouping (high, blue; medium, purple; randomized, red) across sessions of training. Higher values indicate higher entropy. G, Average number of pellets per trial for each predictability level. H, Examples of routes taken by rats on the first trial of the first day (top panels) and after 20 d of training (bottom panels). Color shifts from cyan to yellow as each animal’s trajectory progresses.