Intriguing properties of neural networks [Gaming Neural Networks]

Intriguing properties of neural networks by Christian Szegedy, et al.

Abstract:

Deep neural networks are highly expressive models that have recently achieved state of the art performance on speech and visual recognition tasks. While their expressiveness is the reason they succeed, it also causes them to learn uninterpretable solutions that could have counter-intuitive properties. In this paper we report two such properties.

First, we find that there is no distinction between individual high level units and random linear combinations of high level units, according to various methods of unit analysis. It suggests that it is the space, rather than the individual units, that contains of the semantic information in the high layers of neural networks.

Second, we find that deep neural networks learn input-output mappings that are fairly discontinuous to a significant extend. Specifically, we find that we can cause the network to misclassify an image by applying a certain imperceptible perturbation, which is found by maximizing the network’s prediction error. In addition, the specific nature of these perturbations is not a random artifact of learning: the same perturbation can cause a different network, that was trained on a different subset of the dataset, to misclassify the same input.

Both findings are of interest but the discovery of “adversarial examples” that can cause a trained network to misclassify images, is the more intriguing of the two.

How do you validate a result from a neural network? Possessing the same network and data isn’t going to help if it contains “adversarial examples.” I suppose you could “spot” a misclassification but one assumes a neural network is being used because physical inspection by a person isn’t feasible.

What “adversarial examples” work best against particular neural networks? How to best generate such examples?

How do users of off-the-shelf neural networks guard against “adversarial examples?” (One of those cases where “shrink-wrap” data services may not be a good choice.)

I first saw this in a tweet by Xavier Amatriain

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