Can large language models explore in-context?
Authors: name: Akshay Krishnamurthy, name: Keegan Harris, name: Dylan J. Foster, name: Cyril Zhang, name: Aleksandrs Slivkins

We investigate the extent to which contemporary Large Language Models (LLMs)
can engage in exploration, a core capability in reinforcement learning and
decision making. We focus on native performance of existing LLMs, without
training interventions. We deploy LLMs as agents in simple multi-armed bandit
environments, specifying the environment description and interaction history
entirely in-context, i.e., within the LLM prompt. We experiment with GPT-3.5,
GPT-4, and Llama2, using a variety of prompt designs, and find that the models
do not robustly engage in exploration without substantial interventions: i)
Across all of our experiments, only one configuration resulted in satisfactory
exploratory behavior: GPT-4 with chain-of-thought reasoning and an externally
summarized interaction history, presented as sufficient statistics; ii) All
other configurations did not result in robust exploratory behavior, including
those with chain-of-thought reasoning but unsummarized history. Although these
findings can be interpreted positively, they suggest that external
summarization -- which may not be possible in more complex settings -- is
important for obtaining desirable behavior from LLM agents. We conclude that
non-trivial algorithmic interventions, such as fine-tuning or dataset curation,
may be required to empower LLM-based decision making agents in complex
settings.