What Do Language Models Learn and When? The Implicit Curriculum Hypothesis
Large language models (LLMs) can perform remarkably complex tasks, yet the fine-grained details of how these capabilities emerge during pretraining remain poorly understood. Scaling laws on validation loss tell us how much a model improves with additional compute, but not what skills it acquires in which order. To remedy this, we propose the Implicit Curriculum Hypothesis: pretraining follows a compositional and predictable curriculum across models and data mixtures. We test this by designing a suite of simple, composable tasks spanning retrieval, morphological transformations, coreference, logical reasoning, and mathematics. Using these tasks, we track emergence points across four model families spanning sizes from 410M–13B parameters. We find that emergence orderings of when models reach fixed accuracy thresholds are strikingly consistent ( 𝜌 = .81 across 45 model pairs), and that composite tasks most often emerge after their component tasks. Furthermore, we find that this structur