Analysis on the Dropout Effect in Convolutional Neural Networks

Regularizing neural networks is an important task to reduce overfitting. Dropout [1] has been a widely-used regularization trick for neural networks. In convolutional neural networks (CNNs), dropout is usually applied to the fully connected layers. Meanwhile, the regularization effect of dropout in the convolutional layers has not been thoroughly analyzed in the literature. In this paper, we analyze the effect of dropout in the convolutional layers, which is indeed proved as a powerful generalization method. We observed that dropout in CNNs regularizes the networks by adding noise to the output feature maps of each layer, yielding robustness to variations of images. Based on this observation, we propose a stochastic dropout whose drop ratio varies for each iteration. Furthermore, we propose a new regularization method which is inspired by behaviors of image filters. Rather than randomly drop the activation, we selectively drop the activations which have high values across the feature map or across the channels. Experimental results validate the regularization performance of selective max-drop and stochastic dropout is competitive to the dropout or spatial dropout [2].