Using adversarial gradient integration attribution (Pan et al., 2021), the paper visualizes where each model's attention falls in the frequency domain. The attribution map for CAIT-S/24 shows concentrated attention in the high-frequency region (bottom-right of the DCT spectrum), whereas the map for ResNet-101 shows a more diffuse or low-frequency-biased pattern. The authors generalize this to a class-level claim that ViTs, unlike traditional CNNs, exhibit distinct attention regions in the frequency domain and tend to focus more on high-frequency features. This observation motivates the high-frequency adaptation (HFA) component of their attack method.