We are also interested in how to reduce the side effect of noise on the instance, which may be caused by the failure of sensors or even malicious attacks. We human have the ability to correctly recognise the objects even there are noise (e.g., we can easily recognise human faces under extreme illumination conditions, when partially occluded, or even with heavy makeup); while current machine learning algorithms may not. Recent studies also show that an imperceptible noise on the instance will lead machines to make wrong decisions. All those mean that we human and machines are using different feature extraction mechanisms for making decisions. What are the differences? And how to align them? Answering those questions is very important to build robust and trustworthy machine learning algorithms.