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ClawMachine: Learning to Fetch Visual Tokens for Referential Comprehension
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Proposes ClawMachine, an MLLM that references and grounds objects by emitting groups of quantized visual tokens ("token collectives") in a joint vision-language vocabulary, with hybrid continuous/discrete perception and no extra location syntax.
Problem
Fine-grained referring and grounding in MLLMs currently needs extra syntax (proxy tokens, text coordinates, or location bins) or extra vision modules, which complicates vision-language alignment, training, and inference efficiency.
Approach
Represent a referred region as the set of quantized visual tokens (from LaVIT's VQ codebook) whose patch centers fall inside its box, inserted directly into the text sequence, so referring and grounding become next-token prediction in a joint vocabulary; combine continuous CLIP features (via MLP) with discrete tokens (via LLM embedding) as hybrid perception.
Key results
- ClawMachineX-7B reaches 118.4 CIDEr on RefCOCOg referring and 169.7 CIDEr on Visual Genome, above Groma-7B (107.3 and 158.4).
- ClawMachineX-7B achieves 89.7 / 92.5 / 86.9 on RefCOCO val/test-A/test-B grounding accuracy, the best among listed MLLMs, with Groma-7B (89.5 / 92.1 / 86.2) the closest.
- On Ref-Hal, ClawMachine-7B reaches 75.8 accuracy versus 61.5 for the next-best baseline (Qwen-VL-7B).
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| pre-train with GRIT-20M | ClawMachine-7B · RefCOCOg | METEOR: 17.1 -> 17.4 | Helped |
| pre-train with GRIT-20M | ClawMachine-7B · RefCOCO val | accuracy (IoU 0.5): 88.6 -> 89.7 | Helped |
| add visual referring data to grounding instruction tuning (dual data) (ablation) | ClawMachine · RefCOCO/+/g | REC average score: 1.7% gain | Helped |
| use continuous and discrete image features together instead of continuous features in both stages (ablation) | ClawMachine · RefCOCOg-val | Grounding: 73.1 -> 85.7 | Helped |
| use continuous and discrete image features together instead of discrete features in both stages (ablation) | ClawMachine · VQAv2 | score: 72.1 -> 78.9 | Helped |
| use discrete features in both stages instead of continuous features in both stages (ablation) | ClawMachine · RefCOCOg-val | Grounding: 73.1 -> 84.3 | Helped |
| use discrete features in both stages instead of continuous features in both stages (ablation) | ClawMachine · RefCOCOg-val | Referring: 16.8 -> 14.2 | Hurt |
| replace hybrid features with continuous features in both stages (ablation) | ClawMachine · RefCOCOg-val | Referring: 17.1 -> 16.8 | Hurt |
| replace hybrid features with discrete features in both stages (ablation) | ClawMachine · RefCOCOg-val | Grounding: 85.7 -> 84.3 | Hurt |
| replace token collectives with text coordinates while using hybrid encoding (ablation) | ClawMachine · RefCOCOg | Referring METEOR: 17.1 -> 14.9 | Hurt |
| replace token collectives with text coordinates while using hybrid encoding (ablation) | ClawMachine · RefCOCO val | Grounding: 88.6 -> 81.1 | Hurt |
| replace hybrid encoding with only continuous encoding while using token collectives (ablation) | ClawMachine · RefCOCOg | Referring METEOR: 17.1 -> 15.8 | Hurt |
Surprising findings
- Hybrid perception (continuous plus discrete tokens) gives 85.7 REC versus 73.1 with continuous features only in the ablation table.
- Pre-training on GRIT-20M with 15M pairs yields a better grounding score than the 700K instruction-tuning data alone, indicating scaled pre-training matters more than heavy instruction tuning.
Limitations
- Quantizing visual features loses fine-grained detail.
- The LLM's probabilistic output can yield unstable or incomplete token collectives that miss parts of the target.
- Grounding boxes depend on a separate region sampler with an external detection proposer at inference.
Experimental setup
Datasets: LLaVA-Pretrain ShareGPT-4V RefCOCO/+/g Visual Genome GRIT-20M LLaVA-mix665k Osprey AS-V2 Chatterbox GQA LVIS
Benchmarks: RefCOCOg Visual Genome RefCOCO/+/g LVIS-Ground POPE Ref-Hal LLaVA-Bench (COCO) VQAv2
Metrics: METEOR CIDEr accuracy@IoU0.5 AR accuracy F1 precision recall
Baselines: Shikra-7B Ferret-7B GLaMM-7B Groma-7B Qwen-VL-7B MiniGPT-v2 Florence-2 Osprey-7B GPT4RoI Kosmos-2 Groundhog-7B LLaVA-7B
Builds on: LaVIT LLaVA EVA-CLIP Groma Shikra
Closest papers by meaning
- Don't Show Pixels, Show Cues: Unlocking Visual Tool Reasoning in Language Models via Perception Programs (CVPR 2026 · similarity 0.91)
- LION: Empowering Multimodal Large Language Model with Dual-Level Visual Knowledge (CVPR 2024 · similarity 0.91)
- UniPixel: Unified Object Referring and Segmentation for Pixel-Level Visual Reasoning (NeurIPS 2025 · similarity 0.90)
- Perception Tokens Enhance Visual Reasoning in Multimodal Language Models (CVPR 2025 · similarity 0.90)
- Hugging Visual Prompt and Segmentation Tokens: Consistency Learning for Fine-Grained Visual Understanding in MLLMs (CVPR 2026 · similarity 0.90)
- Ref-Adv: Exploring MLLM Visual Reasoning in Referring Expression Tasks (ICLR 2026 · similarity 0.90)
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