Privacy-Preserving Facial Emotion Classification: A Comprehensive Investigation of Federated Learning Approaches

Facial Emotion Recognition and Classification (FERC) is an important technology used in many areas, but it also brings up serious privacy worries because it depends on sensitive facial information. Federated Learning (FL) is a useful way to handle these issues because it lets different systems train a model together without actually sharing their private data. This paper provides a comprehensive review of the integration of FL with FERC. It surveys key FL methodologies--including horizontal, personalized, and cross-silo FL--applied to emotion classification using architectures such as CNNs and ResNet. The review also identifies critical challenges, such as data heterogeneity, the privacy-performance trade-off, and system heterogeneity, which impact model accuracy and practicality. Future research could focus more on personalized and semi-supervised federated learning, explore cross-modal learning, and look into using blockchain to make the systems more trustworthy. This study emphasizes how FL can help keep user data private while still working well in FERC systems. It’s a useful example for others looking to improve these kinds of systems in the future.