捷径特征作为神经切线核的顶级本征函数:线性神经网络案例及更多
Shortcut Features as Top Eigenfunctions of NTK: A Linear Neural Network Case and More
AI总结:
本文研究了线性神经网络中捷径学习的本征函数特性,并将该结论扩展至更复杂的网络结构。
摘要:
深度学习模型的一个长期问题是捷径学习。在大多数训练数据被某一特定特征主导的情况下,神经网络倾向于学习这种特征,即使该特征无法在训练集之外推广。基于神经切线核(NTK)的框架,我们分析了线性神经网络的情况,以推导捷径学习的一些重要性质。我们定义了神经网络的一个特征作为NTK的本征函数。然后我们发现,当捷径源于聚类分布中样本数量不平衡时,捷径特征对应于具有较大本征值的特征。我们还展示了具有较大本征值的特征在训练后仍对神经网络输出有较大影响,这归因于聚类中的数据方差。这种对某些特征的偏好即使在控制神经网络输出边距时仍存在,这表明最大边距偏见并非捷径学习的唯一主要原因。线性神经网络的这些性质通过实验证明适用于更复杂的神经网络,如两层全连接ReLU网络和ResNet-18。
英文摘要:
One of the chronic problems of deep-learning models is shortcut learning. In a case where the majority of training data are dominated by a certain feature, neural networks prefer to learn such a feature even if the feature is not generalizable outside the training set. Based on the framework of Neural Tangent Kernel (NTK), we analyzed the case of linear neural networks to derive some important properties of shortcut learning. We defined a feature of a neural network as an eigenfunction of NTK. Then, we found that shortcut features correspond to features with larger eigenvalues when the shortcuts stem from the imbalanced number of samples in the clustered distribution. We also showed that the features with larger eigenvalues still have a large influence on the neural network output even after training, due to data variances in the clusters. Such a preference for certain features remains even when a margin of a neural network output is controlled, which shows that the max-margin bias is not the only major reason for shortcut learning. These properties of linear neural networks are empirically extended for more complex neural networks as a two-layer fully-connected ReLU network and a ResNet-18.
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