The escape time vs. the number of escaped participants for human experiments.

Panels a, b and c are for zero obstacle, one obstacle and two obstacles, respectively. The data of the first run (black dots) is above the other two runs in panel a and c, which means the former participants escape slower than the latter ones. In panel b, however, the data of the first run lies between those of the second run and the third run, indicating that the escape speed of the first run is faster than that of the second run and slower than that of the third run. Therefore, the escape time has no correlation with experiments order.