Fig. 3. Average Precision (AP) for each action across varying threshold IoU (tIoU) thresholds on BABEL-TAL-20 (BT-20).

The number of samples per class is annotated in parentheses beside actions in the legend. We notice a disparity in the AP scores for each class, both in terms of their absolute values and their sensitivity to changes in tIoU settings. Specifically, we observe that “run” and “walk” achieve the highest AP scores, whereas “touch body part” exhibits the lowest AP scores. This divergence might stem from the former actions being relatively more distinguishable from other actions, while the latter ones are characterized by greater ambiguity and complexity.