Image-based human re-identification: Which covariates are actually (the most) important?

Human re-identification (re-ID) is nowadays among the most popular topics in computer vision, due to the increasing importance given to safety/security in modern societies. Being expected to sun in totally uncontrolled data acquisition settings (e.g., visual surveillance) automated re-ID not only depends on various factors that may occur in non-controlled data acquisition settings, but - most importantly - performance varies with respect to different subject features (e.g., gender, height, ethnicity, clothing, and action being performed), which may result in highly biased and undesirable automata. While many efforts have been putted in increase the robustness of identification to uncontrolled settings, a systematic assessment of the actual variations in performance with respect to each subject feature remains to be done. Accordingly, the contributions of this paper are threefold: 1) we report the correlation between the performance of three state-of-the-art re-ID models and different subject features; 2) we discuss the most concerning features and report valuable insights about the roles of the various features in re-ID performance, which can be used to develop more effective and unbiased re-ID systems; and 3) we leverage the concept of biometric menagerie, in order to identify the groups of individuals that typically fall into the most common menagerie families (e.g., goats, lambs, and wolves). Our findings not only contribute to a better understanding of the factors affecting re-ID performance, but also may offer practical guidance for researchers and practitioners concerned on human re-identification development.