Point-in-time models showed that knowledge which shifts fastest across web snapshots is also the knowledge that keeps improving late in pretraining
AspireAI community · arXiv
*Not all knowledge is learned at the same time, and pretraining runs treat it as if it is.* Using point-in-time models pretrained on web snapshots from different years, the authors define a temporal variability score - the coefficient of variation of an item's negative log-likelihood across models. A high score means the knowledge is less consistently represented across years of web text.
Across six benchmarks covering diverse topics and six models from multiple open-source families, low- and high-variability items are learned similarly early in training, but high-variability items improve faster later on. By the end of the pretraining run, high-variability items beat low-variability ones in 34 of 36 model-benchmark settings, with an average advantage of 7.3 points of chance-normalized accuracy. The pattern holds most robustly on knowledge-intensive tasks even when comparing items of similar difficulty, which makes the score a diagnostic of learning dynamics beyond aggregate benchmark scores. The limitation: six models across several families is a narrow base, and the score is a retrospective diagnostic rather than something you can steer a run with.
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