Results of experiment 3. ROC curves of the proposed identification system for alignment using manually annotated coordinates of both eyes and mouth (blue solid line), automatically detected eyes (red dashed line), and without applied alignment (green dash-dotted line). (A) Curves for the ChimpZoo dataset. (B) Results for the ChimpTaï dataset. The black solid line denotes the line of equal error. As can be seen, the performance of the algorithm if manually annotated facial markings were used for alignment is only slightly better than alignment using automatically detected facial feature points. The accuracy of the system drops significantly if no alignment was applied at all.