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Title: Improving the robustness of ImageNet classifiers using elements of human visual cognition

Paper content:
We investigate the robustness properties of image recognition models equipped with two features inspired by human vision, an explicit episodic memory and a shape bias, at the ImageNet scale.
As reported in previous work, we show that an explicit episodic memory improves the robustness of image recognition models against small-norm adversarial perturbations under some threat models.
It does not, however, improve the robustness against more natural, and typically larger, perturbations.
Learning more robust features during training appears to be necessary for robustness in this second sense.
We show that features derived from a model that was encouraged to learn global, shape-based representations (Geirhos et al., 2019) do not only improve the robustness against natural perturbations, but when used in conjunction with an episodic memory, they also provide additional robustness against adversarial perturbations.
Finally, we address three important design choices for the episodic memory: memory size, dimensionality of the memories and the retrieval method.
We show that to make the episodic memory more compact, it is preferable to reduce the number of memories by clustering them, instead of reducing their dimensionality.
ImageNet-trained deep neural networks (DNNs) are state of the art models for a range of computer vision tasks and are currently also the best models of the human visual system and primate visual systems more generally (Schrimpf et al., 2018 ).
Yet, they have serious deficiencies as models of human and primate visual systems: 1) they are extremely sensitive to small adversarial perturbations imperceptible to the human eye (Szegedy et al., 2013) , 2) they are much more sensitive than humans to larger, more natural perturbations (Geirhos et al., 2018) , 3) they rely heavily on local texture information in making their predictions, whereas humans rely much more on global shape information (Geirhos et al., 2019; , 4) a fine-grained, image-by-image analysis suggests that images that ImageNet-trained DNNs find hard to recognize do not match well with the images that humans find hard to recognize .
Here, we add a fifth under-appreciated deficiency: 5) human visual recognition has a strong episodic component lacking in DNNs.
When we recognize a coffee mug, for instance, we do not just recognize it as a mug, but as this particular mug that we have seen before or as a novel mug that we have not seen before.
This sense of familiarity/novelty comes automatically, involuntarily, even when we are not explicitly trying to judge the familiarity/novelty of an object we are seeing.
More controlled psychological experiments also confirm this observation: humans have a phenomenally good longterm recognition memory with a massive capacity even in difficult one-shot settings (Standing, 1973; Brady et al., 2008) .
Standard deep vision models, on the other hand, cannot perform this kind of familiarity/novelty computation naturally or automatically, since this information is available to a trained model only indirectly and implicitly in its parameters.
What does it take to address these deficiencies and what are the potential benefits, if any, of doing so other than making the models more human-like in their behavior?
In this paper, we address these questions.
We show that a minimal model incorporating an explicit key-value based episodic memory does not only make it psychologically more realistic, but also reduces the sensitivity to small adversarial perturbations.
It does not, however, reduce the sensitivity to larger, more natural perturbations and it does not address the heavy local texture reliance issue.
In the episodic memory, using features from DNNs that were trained to learn more global shape-based representations (Geirhos et al., 2019) addresses these remaining issues and moreover provides additional robustness against adversarial perturbations.
Together, these results suggest that two basic ideas motivated and inspired by human vision, a strong episodic memory and a shape bias, can make image recognition models more robust to both natural and adversarial perturbations at the ImageNet scale.

assistant: text: This paper proposed to use memory cache to improve robustness against adversarial image examples, and concluded that using a large continous cache is not superior to hard attention.