Prototype Language Models
This work addresses the challenge of efficiently tracing the influence of training samples on outputs in large language models. The authors propose PRISM, an architecture that performs prediction via sparse non-negative prototype mixtures, where each prototype is anchored by clustering objectives to coherent neighborhoods in the training data, thereby explicitly linking predictions to specific training instances. PRISM enables highly efficient attribution—approximately 500× faster than baseline methods—and supports behavior modification without fine-tuning. The approach further incorporates Hessian curvature localization and a linear prototype controller for calibration. Evaluated across models ranging from 130M to 1.6B parameters, PRISM incurs at most a 2.5-point accuracy drop relative to dense baselines on downstream tasks; prototype calibration recovers about 3 points of accuracy, and selective suppression of prototypes can eliminate targeted behaviors without degrading generation quality.