  Large vision-language models (VLMs) fine-tuned on specialized visual
instruction-following data have exhibited impressive language reasoning
capabilities across various scenarios. However, this fine-tuning paradigm may
not be able to efficiently learn optimal decision-making agents in multi-step
goal-directed tasks from interactive environments. To address this challenge,
we propose an algorithmic framework that fine-tunes VLMs with reinforcement
learning (RL). Specifically, our framework provides a task description and then
prompts the VLM to generate chain-of-thought (CoT) reasoning, enabling the VLM
to efficiently explore intermediate reasoning steps that lead to the final
text-based action. Next, the open-ended text output is parsed into an
executable action to interact with the environment to obtain goal-directed task
rewards. Finally, our framework uses these task rewards to fine-tune the entire
VLM with RL. Empirically, we demonstrate that our proposed framework enhances
the decision-making capabilities of VLM agents across various tasks, enabling
7b models to outperform commercial models such as GPT4-V or Gemini.
Furthermore, we find that CoT reasoning is a crucial component for performance
improvement, as removing the CoT reasoning results in a significant decrease in
the overall performance of our method.
