---
language:
- en
---

**lexdec-medium-char** is a small, autoregressive llama model featuring character-level tokenization, trained on the 2024/2025 [BabyLM dataset](https://osf.io/ryjfm/). The *checkpoints* branch contains 19 checkpoints, 10 across the first 10% of pretraining and 9 more for the remaining 9 percent of pretraining. 

We used this model to trace the development of linguistic knowledge (word-level, syntax) across pretraining and to compare it to both larger character-level models and comparable subword models:

|  | [small-char](https://huggingface.co/bbunzeck/lexdec-small-char) | [medium-char](https://huggingface.co/bbunzeck/lexdec-medium-char) | [large-char](https://huggingface.co/bbunzeck/lexdec-large-char) | [small-bpe](https://huggingface.co/bbunzeck/lexdec-small-bpe) | [medium-bpe](https://huggingface.co/bbunzeck/lexdec-medium-bpe) | [large-bpe](https://huggingface.co/bbunzeck/lexdec-large-bpe) |
|---|---:|---:|---:|---:|---:|---:|
| Embedding size | 128 | 256 | 512 | 128 | 256 | 512 |
| Hidden size | 128 | 256 | 512 | 128 | 256 | 512 |
| Layers | 4 | 8 | 12 | 4 | 8 | 12 |
| Attention heads | 4 | 8 | 12 | 4 | 8 | 12 |
| Context size | 128 | 128 | 128 | 128 | 128 | 128 |
| Vocab. size | 102 | 102 | 102 | 8,002 | 8,002 | 8,002 |
| Parameters | 486,016 | 3,726,592 | 21,940,736 | 2,508,416 | 7,771,392 | 30,030,336 |

If you use this model, please cite the following preprint (the final version will be added as soon as it is published):

```
@misc{bunzeck2025subwordmodelsstruggleword,
      title={Subword models struggle with word learning, but surprisal hides it}, 
      author={Bastian Bunzeck and Sina Zarrieß},
      year={2025},
      eprint={2502.12835},
      archivePrefix={arXiv},
      primaryClass={cs.CL},
      url={https://arxiv.org/abs/2502.12835},}
```