Towards Open Environments and Instructions: General Vision-Language Navigation via Fast-Slow Interactive Reasoning
Yang Li, Aming Wu, Zihao Zhang, Yahong Han

TL;DR
This paper introduces a dynamic fast-slow reasoning framework for vision-language navigation, enabling agents to adapt to diverse and unseen environments by enhancing generalization through interactive cognition modules.
Contribution
It proposes a novel fast-slow interactive reasoning framework that improves generalization in open-world VLN tasks by continuously optimizing fast decision-making with slow reflection.
Findings
Outperforms existing methods in generalization to unseen environments
Enhances navigation accuracy through fast-slow reasoning interaction
Demonstrates robustness in diverse and inconsistent instructions
Abstract
Vision-Language Navigation (VLN) aims to enable agents to navigate to a target location based on language instructions. Traditional VLN often follows a close-set assumption, i.e., training and test data share the same style of the input images and instructions. However, the real world is open and filled with various unseen environments, posing enormous difficulties for close-set methods. To this end, we focus on the General Scene Adaptation (GSA-VLN) task, aiming to learn generalized navigation ability by introducing diverse environments and inconsistent instructions.Recent research indicates that by means of fast and slow cognition systems, human beings could generate stable policies, which strengthen their adaptation for open world. Inspired by this idea, we propose the slow4fast-VLN, establishing a dynamic interactive fast-slow reasoning framework. The fast-reasoning module, an…
Peer Reviews
Decision·ICLR 2026 Conference Withdrawn Submission
**Innovative Cognitive Framework:** The idea of *interactive* fast–slow reasoning—where System 2 (slow reflection) directly updates and empowers System 1 (fast policy)—is an elegant adaptation of dual-process cognition to embodied VLN. Unlike previous “parallel” designs, this model establishes a genuine feedback loop, forming a “slow-reflection-feeds-fast-action” mechanism. **Integration of LLM Reflection in Embodied Learning:** The slow reasoning module uses structured Chain-of-Thought (CoT) p
**1. Conceptual Novelty—Limited Algorithmic Depth:** While the interactive fast–slow loop is well presented, it remains conceptually similar to existing *dual-process* or *meta-reflection* frameworks in VLN (e.g., MiC 2024, VLN-Copilot 2024, CogDDN 2025; SE-VLN 2025; NavCoT 2025) and in general LLM reasoning (e.g., Fast-Slow LLM 2025). The “interaction” here mainly consists of attention-based fusion (Eq. 7–9) between retrieved experience embeddings and visual features—a modest engineering extens
- The paper focuses on open-world generalization in VLN, a direction gaining traction in embodied AI and multimodal reasoning. The use of dual-process cognition (fast and slow reasoning) to structure VLN decision processes is interesting and aligns with ongoing efforts to bring cognitive inspiration into LLM-augmented agents. - The use of GSA-R2R, which extends R2R with out-of-distribution scenes and diverse instruction styles, is suitable for testing generalization. - The paper includes ablat
- While the fast–slow reasoning framework is well-motivated conceptually, its technical realization mainly combines existing components (DUET backbone + LLM-based reflection + attention fusion). The interaction between fast and slow reasoning is implemented as an experience retrieval and attention fusion module, which feels incremental rather than a fundamentally new reasoning paradigm. - The reported improvements over GR-DUET are small (typically +1–2% SR), which may fall within noise levels g
Current navigation methods often lack robustness and perform poorly in out-of-distribution (OOD) environments. The dual-system framework may offer a promising solution to this challenge by enhancing the generalization ability of navigation systems.
I am looking for some experiments testing on real mobile robots. the current testing results is trying to show it has good performance on out of distribution data. I think this is the key motivation of the paper. how about training with offline dataset but testing in real world. like is it solving the simtoreal problem simultaneously?
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Taxonomy
TopicsMultimodal Machine Learning Applications · Reinforcement Learning in Robotics · Constraint Satisfaction and Optimization
