Neologism Learning as a Parameter-Efficient Alternative to Fine-Tuning for Model Steering

Fuente: arXiv
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Main Authors: Park, Sungjoon, Ramamurthi, Varun, Terry, Owen
Format: Preprint
Published: 2025
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author Park, Sungjoon
Ramamurthi, Varun
Terry, Owen
author_facet Park, Sungjoon
Ramamurthi, Varun
Terry, Owen
contents In language modeling, neologisms are new tokens trained to represent a concept not already included in a given model's vocabulary. Neologisms can be used to encourage specific behavior in models, for example by appending prompts with "Give me a neologism answer." Behavioral steering can also be achieved through fine-tuning, albeit with more compute and less flexibility: learning a neologism only trains d parameters and allows the user to still access the model's default behavior. We compare the performance of neologism learning against low-rank adaptation (LoRA) fine-tuning, finding that neologisms outperform fine-tuned models under a matched training setup (same data and hyperparameters). We also investigate self-verbalizations of neologisms, and observe that the model will occasionally make up its own new words when asked about a neologism.
format Preprint
id arxiv_https___arxiv_org_abs_2512_18551
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Neologism Learning as a Parameter-Efficient Alternative to Fine-Tuning for Model Steering
Park, Sungjoon
Ramamurthi, Varun
Terry, Owen
Computation and Language
In language modeling, neologisms are new tokens trained to represent a concept not already included in a given model's vocabulary. Neologisms can be used to encourage specific behavior in models, for example by appending prompts with "Give me a neologism answer." Behavioral steering can also be achieved through fine-tuning, albeit with more compute and less flexibility: learning a neologism only trains d parameters and allows the user to still access the model's default behavior. We compare the performance of neologism learning against low-rank adaptation (LoRA) fine-tuning, finding that neologisms outperform fine-tuned models under a matched training setup (same data and hyperparameters). We also investigate self-verbalizations of neologisms, and observe that the model will occasionally make up its own new words when asked about a neologism.
title Neologism Learning as a Parameter-Efficient Alternative to Fine-Tuning for Model Steering
topic Computation and Language
url https://arxiv.org/abs/2512.18551