Consistency for Large Neural Networks

Neural networks have shown remarkable success, especially in overparameterized or "large" models. Despite increasing empirical evidence and intuitive understanding, a formal mathematical justification for the behavior of such models, particularly regarding overfitting, remains incomplete. In this paper, we prove that the Mean Integrated Squared Error (MISE) of neural networks with either $L^1$ or $L^2$ penalty decreases after a certain model size threshold, provided that the sample size is sufficiently large, and achieves nearly the minimax optimality in the Barron space. These results challenge conventional statistical modeling frameworks and broadens recent findings on the double descent phenomenon in neural networks. Our theoretical results also extend to deep learning models with ReLU activation functions.