cs.CVJun 3, 2026

Horse Eye Blink Detection and Classification for Equine Affective State Assessment

Authors: João AlvesSigne Møller-SkuldbølPia Haubro AndersenRikke Gade

Organizations: Visual Analysis and Perception Lab, Aalborg University · Department of Animal Biosciences, Swedish University of Agricultural Sciences

Abstract

Automated detection of equine facial action units (AUs) is a promising yet under-explored avenue for pain and affective state assessment in horses. Half and full-blink movements are recognised indicators of pain and stress, but as micro-expressions, their subtle, fine-grained nature makes them easily missed by the naked eye and only discernible through frame-by-frame video inspection, making reliable automated detection from video a particularly demanding task. We develop and evaluate three methods for automated blink classification from horse videos: a frame-based YOLOv12 detector, an optical flow magnitude thresholding approach, and a fine-tuned VideoMAE model, tested on a publicly available dataset. We achieve a macro-F1 score of 0.898 when doing blink classification and 0.926 on binary blink detection. Our results highlight both the potential and the inherent challenges of fine-grained AU detection for equine welfare monitoring.

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