Title: Escaping Model Collapse via Synthetic Data Verification:  Near-term Improvements and Long-term Convergence
Primary area: learning theory
Keywords: Model Collapse, Synthetic Data, Verifier-guided retraining

Abstract: Synthetic data has been increasingly used to train frontier generative models. However, recent study raises key concerns that iteratively retraining a generative model on its self-generated synthetic data may keep deteriorating model performance, a phenomenon often coined model collapse. In this paper, we investigate ways to modify the synthetic retraining process to avoid model collapse, and even possibly help reverse the trend from collapse to improvement. Our key finding is that by injecting information through an external synthetic data verifier, whether a human or a better model, synthetic retraining will not cause model collapse. Specifically, we situate our theoretical analysis in the fundamental linear regression problem, showing that verifier-guided retraining yields early improvements when the verifier is accurate, and in the long run, the parameter estimate converges to the verifier’s knowledge center. Our theory predicts that the performance of synthetic retraining will have early gains but eventually plateaus or even reverses, unless the verifier is perfectly reliable. Indeed, our experiments on both linear regression as well as  Conditional Variational Autoencoder (CVAE) trained on MNIST data also confirm these theoretical insights.