Weakly Supervised Learning for Facial Behavior Analysis : A Review
Facial behavior analysis faces significant weakly supervised learning challenges, including high annotation costs, reliance on domain experts, ambiguous intensity labeling, and expert bias. To address these issues, this paper presents a systematic survey of weakly supervised learning methods for facial expression recognition and action unit detection in real-world scenarios. We propose the first unified weak supervision taxonomy encompassing both categorical and dimensional labels, explicitly characterizing core challenges such as label ambiguity and intensity bias. Methodologically, we introduce an integrated framework combining label-noise-robust training, multiple-instance learning, bag-level ranking supervision, self-training, and consistency regularization. Extensive evaluation—standardized across 12+ benchmark datasets and 30+ baseline methods—demonstrates the effectiveness and generalizability of our approach. Our work advances the practical deployment of facial behavior models under limited or imperfect supervision.