Guiding Large Language Models via Directional Stimulus Prompting

We introduce a new framework, Directional Stimulus Prompting, that uses a tuneable language model (LM) to provide guidance for the black-box frozen large language model (LLM) on downstream tasks. Unlike prior work that manually or automatically finds the optimal prompt for each task, we train a policy LM to generate discrete tokens as ``directional stimulus'' of each input, which is a hint/cue such as keywords of an article for summarization. The directional stimulus is then combined with the original input and fed into the LLM to guide its generation toward the desired target. The policy LM can be trained through 1) supervised learning from annotated data and 2) reinforcement learning from offline and online rewards to explore directional stimulus that better aligns LLMs with human preferences. This framework is flexibly applicable to various LMs and tasks. To verify its effectiveness, we apply our framework to summarization and dialogue response generation tasks. Experimental results demonstrate that it can significantly improve LLMs' performance with a small collection of training data: a T5 (780M) trained with 2,000 samples from the CNN/Daily Mail dataset improves Codex (175B)'s performance by 7.2% in ROUGE-Avg scores; 500 dialogues boost the combined score by 52.5%, achieving comparable or even better performance than fully trained models on the MultiWOZ dataset.