RA-Det: Towards Universal Detection of AI-Generated Images via Robustness Asymmetry
This addresses the reliability issue in downstream recognition systems caused by photo-realistic AI-generated images, offering a model-agnostic solution that is incremental in its behavioral approach.
The paper tackles the problem of detecting AI-generated images by shifting from appearance-based to behavior-based detection, identifying robustness asymmetry as a universal signal where generated images show larger feature drift under perturbations than natural images, and introduces RA-Det, which improves average detection performance by 7.81% across 14 generative models.
Recent image generators produce photo-realistic content that undermines the reliability of downstream recognition systems. As visual appearance cues become less pronounced, appearance-driven detectors that rely on forensic cues or high-level representations lose stability. This motivates a shift from appearance to behavior, focusing on how images respond to controlled perturbations rather than how they look. In this work, we identify a simple and universal behavioral signal. Natural images preserve stable semantic representations under small, structured perturbations, whereas generated images exhibit markedly larger feature drift. We refer to this phenomenon as robustness asymmetry and provide a theoretical analysis that establishes a lower bound connecting this asymmetry to memorization tendencies in generative models, explaining its prevalence across architectures. Building on this insight, we introduce Robustness Asymmetry Detection (RA-Det), a behavior-driven detection framework that converts robustness asymmetry into a reliable decision signal. Evaluated across 14 diverse generative models and against more than 10 strong detectors, RA-Det achieves superior performance, improving the average performance by 7.81 percent. The method is data- and model-agnostic, requires no generator fingerprints, and transfers across unseen generators. Together, these results indicate that robustness asymmetry is a stable, general cue for synthetic-image detection and that carefully designed probing can turn this cue into a practical, universal detector. The source code is publicly available at Github.