Recall that the structural similarity score of the start node is 66.0 (arb. unit) and the minimum, the maximum, the mean and the standard deviation of the score are 0.0, 119.0, 55.8, and 16.2, respectively (see also Figure ). In the Greedy search it was found that most sampled nodes with the minimum path length of 1 tend to have relatively large scores, e.g., 56.8, 57.7, or 62.5, while frequently selected nodes with minimum path lengths of 3 and 4 have scores such as 35.7, 31.9, and 42.7, which are smaller than those of the typical scores of the sampled nodes with the minimum path length of 1. This makes nodes with the minimum path length of 1 less likely to be chosen because the node will be chosen according to the scores. Since reaching the goal requires selecting nodes with the minimum path length of 1, this selection bias leads to the poorest performance of Greedy in Figure . Unlike for the Greedy policy, for the Random policy, the fraction of nodes possessing a minimum path length of greater than 4 is higher (approximately 0.4), indicating that the Random policy select nodes apart from the goal node. In contrast, for Random, the fraction of nodes possessing minimum path lengths of 3 and 4 is much lower than the fraction of such nodes for Greedy. Furthermore, for Random, although the fractions of nodes possessing minimum path lengths of 2 and 1 are not as extremely small as the fractions of such nodes for Greedy, it is yet relatively small, which results in a relatively poor goal finding. Overall, Uniform shows a trend similar to that of Random rather than that of Greedy but with larger initial fractions of nodes possessing minimum path lengths of 2 and 1, corresponding to faster initial growth of the goal finding rate in Figure . This is because, in contrast to Random, Uniform prioritized newly discovered nodes.