Natural Language Explanation (NLE) in vision and language tasks aims to provide human-understandable explanations for the associated decision-making process. In practice, one might encounter explanations which lack informativeness or contradict visual-grounded facts, known as \textit{implausibility} and \textit{hallucination} problems, respectively. To tackle these challenging issues, we consider the task of visual question answering (VQA) and introduce \textit{Rapper}, a two-stage \textbf{R}einforced R\textbf{a}tionale-\textbf{P}rom\textbf{p}t\textbf{e}d Pa\textbf{r}adigm. By knowledge distillation, the former stage of \textit{Rapper} infuses rationale-prompting via large language models (LLMs), encouraging the rationales supported by language-based facts. As for the latter stage, a unique Reinforcement Learning from NLE Feedback (RLNF) is introduced for injecting visual facts into NLE generation. Finally, quantitative and qualitative experiments on two VL-NLE benchmarks show that \textsc{Rapper} surpasses state-of-the-art VQA-NLE methods while providing plausible and faithful NLE.
RAPPER: Reinforced Rationale-Prompted Paradigm for Natural Language Explanation in Visual Question Answering
Kai-Po Chang Chi-Pin Huang Wei-Yuan Cheng Fu-En Yang Chien-Yi Wang Yung-Hsuan Lai Yu-Chiang Frank Wang