Typical performance of participants on instance 22.

A) Participant finds the optimal solution in 16 trials. The solutions and lengths are depicted. B) Move quality for trials 2 and thereafter. For example, the first move shows the modifications performed to the better solution so far (solution of trial 1) to achieve solution of trial 2. As another example, the 6th move shows the modification performed to the better solution so far (solution of trial 4) to achieve solution of trial 7. A good modification (shown in black) is either to keep an edge that belongs to the optimum or to remove an edges not in the optimum. The remaining modifications are shown in red.