Extended Data Fig. 1: Behavioural measures in the ABCD task.

a) Three example connection configurations for the pre-selection and pre-training sessions done before exposure to the first ABCD task. Here a subset of 5-7 maze locations (nodes) were available to the mouse and each node was rewarded provided the animal did not just receive reward in the same node. b) Tasks were designed such that task space and physical space are orthogonal to each other. Left: schematic showing that optimal path lengths between rewarded goals differed both within and between tasks. Right: a bar plot showing that the task space “distances” between reward locations (how many task states are between the rewards) are not correlated with the physical distances in the maze (the optimal number of steps taken to reach reward). Data points represent individual mice, where physical distances are averaged across all tasks experienced by a given mouse. Pearson correlation: r = 6.04 × 10-18 P = 1.0; one-way ANOVA statistic=2.02, P = 0.147, df = 12 c). Example paths from 3 different mice performing 3 different tasks. Each row is a set of 5 consecutive trials from the same mouse and task. Single trial paths are superimposed upon whole session coverage shown in grey. Mice rapidly converged on near-optimal routes and used only a subset of the available paths. d) Reward sequences showed minimal correlation across all tasks in all mice (left) and no correlations on all tasks for mice where neuronal data was recorded (7/13 mice middle) or on the late 3 task days from neural mice (right). Note that electrophysiological data in this manuscript is all collected from the late 3 task days. T-test (two-sided) against 0 correlation: all tasks: N = 13 mice, r = 0.002, statistic=2.91, P = 0.013, df = 12; all tasks from neural mice (mice where neuronal data was recorded): N = 7 mice, r = 0.002, statistic=1.81, P = 0.120, df = 6; tasks on Late 3-task days from neural mice (tasks where neural data was recorded): N = 7 mice, r = 4.5 × 10⁻⁴, statistic=0.22, P = 0.634, df = 6. e) Animals used stereotyped routes when taking the shortest route to a goal. The entropy of correct transitions taken is lower than expected if animals took all shortest routes equally. T-test (two-sided) against 1 – N = 13 animals, statistic = −23.6, P = 1.96 × 10⁻¹¹, df = 12 f) Performance is unaffected by the inclusion of a tone at reward a. 3 mice were exposed to additional tasks (after completing task 40) where the tone at a was randomly omitted in 50% of trials. The tone or no-tone status of a trial refers to whether the tone was omitted at the a at the beginning of the trial. Left: mean proportion of transitions where one of the shortest routes was taken N = 26 tasks, Wilcoxon test (two-sided); statistic=164, P = 0.784. Right: mean relative path distance N = 26 tasks, Wilcoxon test (two-sided): statistic=130, P = 0.258 g). Performance on the d-to-a transition is unaffected by the inclusion of a tone at reward a in the previous trial: Left: mean proportion of transitions where one of the shortest routes was taken N = 26 tasks, Wilcoxon test (two-sided); statistic=134, P = 0.903. Right: mean relative path distance N = 26 tasks, Wilcoxon test (two-sided): statistic=149, P = 0.515 h). Suboptimal performance was associated with persisting behavioural biases from before exposure to the task. Y-axis shows the r value calculated from a correlation between the mean relative path distance taken between goals and the probability the steps within this trajectory would have been taken when the animal was naive to any ABCD task (when the animal explored the arena before any rewards or tasks were presented). A net positive correlation indicates that when animals take longer routes (i.e. perform less optimally) they take these routes through steps that they were more likely to take before exposure to any ABCD task. T-test (two-sided) against 0 – N = 13 animals, statistic=2.70, P = 0.019, df = 12 i). Mean relative path distance travelled by the mice between goals in the first 20 trials of early vs late tasks. Wilcoxon test (two-sided) N = 13 animals, Statistic=0.0, P = 2.44 × 10⁻⁴ j). Mean proportion of transitions where one of the shortest routes was taken in the first 20 trials of early vs late tasks. Wilcoxon test (two-sided) N = 13 animals, Statistic=10.0 P = 0.010 k) Mean proportion of “perfect trials” where all transitions (a → b, b → c, c → d and d → a) in a given trial were taken via the shortest route. Left: scatter plot of mean proportion of perfect trials in the first 20 trials of early vs late tasks. Wilcoxon test (two-sided) N = 13 animals, Statistic=11.0 P = 0.028. Right: bar plot of the same data showing that, for both early and late tasks, the proportion of perfect trials is significantly above chance: T-test (two-tailed) against chance (0.007): Early tasks statistic=2.55, P = 0.025; Late tasks - statistic=4.06, P = 0.002. l) ABCDE task performance (relative path distance): after completing at least 40 ABCD tasks, two animals completed additional ABCDE tasks (11 and 13 tasks each) where tasks comprised a loop of 5 (instead of 4) rewards. Animals readily performed above chance in the first 20 trials, as demonstrated by comparing path length between goals to the shortest possible path (i.e. computing a “relative path distance” measure). T-test (two-sided) against chance (6.44): N = 24 tasks, statistic = −30.0 P = 6.18 × 10⁻²⁰, df = 23. Chance level was calculated empirically using the mean relative path distance across the first trial of the first 5 ABCD tasks. m) ABCDE task performance (proportion correct transitions): animals readily performed above chance in the first 20 trials, as demonstrated by quantifying the proportion of transitions where animals took the shortest possible path. Wilcoxon test (two-sided): N = 24 tasks, statistic=0.0, P = 1.19 × 10⁻⁷. Chance levels were derived empirically for each mouse using baseline transition probabilities calculated when animals explored the maze before experiencing any ABCD tasks: see Methods under “Behavioural Scoring”. n) No difference in the empirical chance levels (baseline transition probabilities calculated when animals explored the maze before experiencing any ABCD tasks: see Methods under “Behavioural Scoring”) between d-to-a and c-to-a/b-to-a transitions on the first trial in early (left) and late (right) tasks. Wilcoxon test (two-sided); Early tasks: N = 13 animals, statistic=42.0, P = 0.839; Late tasks: N = 13 animals, statistic=43.0, P = 0.893 o). No difference in the analytical chance levels (see Methods under “Behavioural Scoring”) between d to a and c-to-a/b-to-a transitions on the first trial in early (left) and late (right) tasks. Wilcoxon test (two-sided); Early tasks: N = 13 animals, statistic=20.0, P = 0.080; Late tasks: N = 13 animals, statistic=32.0, P = 0.376 p). No difference in the shortest physical maze distances between d-to-a and c-to-a/b-to-a transitions on the first trial in early (left) and late (right) tasks. Wilcoxon test (two-sided); Early tasks: N = 13 animals, statistic=16.0, P = 0.071; Late Tasks: N = 13 animals, statistic=25.0, P = 0.477 q) Zero-shot inference on the first trial of late tasks is associated with animals returning from d to a more often than d-to-b or d-to-c. The proportion of tasks in which animals took the most direct path from d-to-a on the first trial is compared to the same measure but for premature returns from d-to-b and d-to-c. Early tasks are shown on the left and late tasks on the right. Wilcoxon test (two-sided); Early tasks: N = 13 animals, statistic=27.0, P = 0.594; N = 13 animals, Late tasks: statistic=6.0, P = 0.016 All error bars represent the standard error of the mean.