Visual Grounding First, Multimodal In-context Learning Follows
Organizations: UC Berkeley · Seoul National University · Xero · MIT CSAIL ·
Abstract
LLMs have shown strong in-context learning (ICL) capability, but extending it to Multimodal LLMs (MLLMs) remains challenging. Prior multimodal ICL methods often rely on ICL-specific datasets for additional training or task vector extraction, which can improve performance on the same ICL benchmark used for adaptation. However, they do not generalize well to other benchmarks and often induce forgetting in previously well-solved tasks. For this reason, we identify 'visual grounding' as the key bottleneck in multimodal ICL; MLLMs often fail to attend to task-relevant visual evidence in demonstrations, instead over-relying on textual cues and producing hallucinated outputs. To address this, we propose ProCoRe to enhance visual grounding through contrastive reinforcement learning on multimodal contrastive data for improving multimodal ICL. ProCoRe generates captions for contrastive image pairs, decomposes them into propositions, and optimizes contrastive rewards that encourage alignment with corresponding images while discouraging mismatched ones. Despite never seeing ICL-formatted training examples, ProCoRe improves average multimodal ICL classification accuracy by 5.6% and captioning ROUGE-L by 13.8% over the off-the-shelf Qwen-VL-3-8B model, outperforming ICL-data-dependent state of the arts across benchmarks. Finally, we introduce PICL, a personalized multimodal ICL captioning benchmark that tests whether MLLMs genuinely understand visual demonstrations rather than relying on pre-trained semantic priors.
Figures & tables
| Category | ICL Training Dataset | Method | MS COCO | PICL | ||||||||
| 0-shot | 1-shot | 2-shot | 4-shot | 8-shot | 0-shot | 1-shot | 2-shot | 3-shot | 4-shot | |||
| Off-the-shelf | - | - | 15.53 | 19.02 | 21.21 | 23.52 | 25.65 | 24.50 | 25.40 | 24.78 | 28.30 | 29.29 |
| Retrieval and ordering | - | RICES (NeurIPS22) | 15.53 | 19.02 | 21.08 | 23.36 | 25.70 | 24.50 | 25.40 | 26.44 | 27.14 | 28.20 |
| VICL (ACL24) | 17.41 | 21.52 | 23.44 | 24.16 | 27.63 | 23.12 | 26.77 | 27.38 | 25.96 | 29.41 | ||
| MMICES (WACV25) | 15.53 | 19.02 | 21.65 | 22.52 | 25.16 | 24.50 | 25.40 | 21.70 | 23.82 | 24.79 | ||
| Task vector | MS COCO | MTV (NeurIPS24) | 15.84 | 18.36 | 18.68 | 18.53 | 19.02 | 12.11 | 15.02 | 16.41 | 15.88 | 17.63 |
| Category | ICL Training Dataset | Method | TrueMICL | ISEKAI | ||||||||
| 0-shot | 1-shot | 2-shot | 4-shot | 8-shot | 0-shot | 2-shot | 4-shot | 8-shot | 12-shot | |||
| Off-the-shelf | - | - | 27.11 | 44.79 | 48.83 | 55.03 | 62.70 | 0.16 | 37.98 | 83.68 | 93.79 | 96.42 |
| Retrieval and ordering | - | RICES (NeurIPS22) | 27.11 | 44.79 | 47.16 | 51.83 | 61.86 | 0.16 | 36.31 | 81.21 | 90.53 | 92.36 |
| VICL (ACL24) | 28.22 | 45.44 | 50.01 | 55.12 | 61.80 | 1.12 | 37.81 | 74.64 | 88.93 | 88.41 | ||
| MMICES (WACV25) | 27.11 | 44.79 | 48.40 | 58.07 | 63.04 | 0.16 | 34.55 | 73.09 | 85.27 | 84.87 | ||
| Task vector | TrueMICL | MTV (NeurIPS24) | 23.80 | 36.45 | 42.52 | 45.30 | 55.70 | 3.04 | 32.88 | 81.98 | 94.99 | 90.12 |
| Method | MS COCO | PICL | ||||||||
| 0-shot | 1-shot | 2-shot | 4-shot | 8-shot | 0-shot | 1-shot | 2-shot | 3-shot | 4-shot | |
| Off-the-Shelf (Qwen-VL-3-8B) | 15.53 | 19.02 | 21.21 | 23.52 | 25.65 | 24.50 | 25.40 | 24.78 | 28.30 | 29.29 |
| SFT | 19.48 | 27.92 | 30.11 | 26.84 | 37.62 | 22.13 | 27.88 | 23.41 | 30.74 | 26.81 |
| Sentence-Level Contrastive Reward | 36.02 | 45.73 | 43.21 | 44.11 | 42.58 | 32.88 | 34.74 | 31.92 | 34.02 | 33.41 |
| ProCoRe ( Ours ) | 39.12 | 46.88 | 46.41 | 46.26 | 46.03 | 33.54 | 36.11 | 34.89 | 36.71 | 36.76 |
Appendix figures & tables19 assets
Supplementary material from the paper’s appendix.
Appendix
| Metric | Mean SD | Median |
| Agreement (%) | ||
| Cohen’s | ||
| Precision (%) | ||
| Recall (%) | ||
| F1-score (%) | ||
| Raw score (/30) |
| Category | Method | PICL-PororoSV | |||
| 1-shot | 2-shot | 3-shot | 4-shot | ||
| Off-the-shelf | - | 38 | 21 | 29 | 31 |
| Retrieval and ordering | RICES (NeurIPS22) | 33 | 27 | 29 | 35 |
| VICL (ACL24) | 36 | 28 | 30 | 35 | |
| MMICES (WACV25) | 30 | 24 | 27 | 32 | |
| Task vector | MTV (NeurIPS24) | 34 | 13 | 26 | 25 |
| Proposition Decomposer | 0-shot | 1-shot | 2-shot | 4-shot |
| GPT | ||||
| Qwen3-1.7B | ||||
| LLaMA3.2-3B | ||||
| Qwen3-4B |
| Proposition Decomposer | 0-shot | 1-shot | 2-shot | 4-shot |
| GPT | ||||
| Qwen3-1.7B | ||||
| LLaMA3.2-3B | ||||
| Qwen3-4B |
| Method | 1-shot | 2-shot | 3-shot | 4-shot |
| Off-the-shelf | 23.33 | 27.00 | 31.67 | 29.00 |
| SFT | 9.67 | 9.33 | 15.67 | 10.33 |
| No-proposition-decomposition | 42.67 | 38.67 | 40.00 | 32.00 |
| Image contrastive only ( ) | 40.00 | 42.67 | 37.67 | 30.33 |
| Text contrastive only ( ) | 33.00 | 30.33 | 31.67 | 32.00 |
| No shared-content reward ( ) | 53.33 | 38.00 | 44.00 | 39.67 |
| Method | 0-shot | 1-shot | 2-shot | 4-shot | 8-shot |
| Off-the-shelf | 15.53 | 19.02 | 21.21 | 23.52 | 25.65 |
| SFT | 19.48 | 27.92 | 30.11 | 26.84 | 37.62 |
| No-proposition-decomposition | 36.02 | 44.73 | 43.21 | 44.11 | 42.58 |
| Image contrastive only ( ) | 22.91 | 35.44 | 29.37 | 33.88 | 31.26 |
| Text contrastive only ( ) | 24.12 | 36.91 | 27.54 | 34.26 | 28.93 |
| No shared-content reward ( ) | 30.06 | 30.58 | 30.11 | 35.49 | 37.82 |
| Category | ICL Training Dataset | Method | VL-ICL | MIC | ||||||||
| 0-shot | 1-shot | 2-shot | 4-shot | 8-shot | 0-shot | 1-shot | 2-shot | 4-shot | 8-shot | |||
| Off-the-shelf | - | - | 19.29 | 45.13 | 59.25 | 57.42 | 63.25 | 16.49 | 24.90 | 30.23 | 35.48 | 42.46 |
| Retrieval and ordering | - | RICES (NeurIPS22) | 19.29 | 45.13 | 44.67 | 53.13 | 57.88 | 16.49 | 24.90 | 30.70 | 37.32 | 45.48 |
| VICL (ACL24) | 15.84 | 41.72 | 41.03 | 53.68 | 58.21 | 14.11 | 27.42 | 32.88 | 33.21 | 45.03 | ||
| MMICES (WACV25) | 19.29 | 45.13 | 44.08 | 53.33 | 59.84 | 16.49 | 24.90 | 30.68 | 36.62 | 41.94 | ||
| Task vector | VL-ICL | MTV (NeurIPS24) | 20.96 | 37.79 | 38.92 | 44.04 | 48.88 | 33.74 | 35.21 | 36.02 | 37.88 | 38.41 |
| Category | ICL Training Dataset | Method | MS COCO | PICL | ||||||||
| 0-shot | 1-shot | 2-shot | 4-shot | 8-shot | 0-shot | 1-shot | 2-shot | 3-shot | 4-shot | |||
| Off-the-shelf | - | Random | 26.92 | 31.22 | 33.25 | 35.83 | 36.26 | 18.44 | 21.86 | 24.56 | 25.84 | 28.01 |
| Retrieval and ordering | - | RICES (NeurIPS22) | 26.92 | 31.22 | 31.84 | 33.70 | 35.41 | 18.44 | 21.86 | 25.01 | 26.31 | 27.08 |
| VICL (ACL24) | 27.14 | 32.81 | 35.02 | 37.06 | 36.41 | 18.72 | 23.11 | 23.56 | 24.84 | 27.01 | ||
| MMICES (WACV25) | 26.92 | 31.22 | 29.62 | 33.71 | 36.65 | 18.44 | 21.86 | 20.01 | 20.99 | 23.31 | ||
| Task vector | MS COCO | MTV (NeurIPS24) | 22.56 | 22.75 | 24.40 | 25.00 | 26.63 | 9.84 | 13.72 | 12.06 | 12.88 | 11.91 |
| Category | ICL Training Dataset | Method | MS COCO | PICL | ||||||||
| 0-shot | 1-shot | 2-shot | 4-shot | 8-shot | 0-shot | 1-shot | 2-shot | 3-shot | 4-shot | |||
| Off-the-shelf | - | Random | 27.57 | 31.78 | 33.47 | 34.11 | 33.99 | 15.68 | 14.58 | 17.37 | 16.82 | 19.95 |
| Retrieval and ordering | - | RICES (NeurIPS22) | 27.57 | 31.78 | 33.29 | 33.05 | 34.06 | 15.68 | 14.58 | 18.27 | 22.19 | 25.02 |
| VICL (ACL24) | 26.01 | 33.02 | 34.56 | 34.73 | 35.21 | 16.41 | 15.92 | 15.36 | 21.88 | 21.47 | ||
| MMICES (WACV25) | 27.57 | 31.78 | 33.48 | 33.83 | 33.74 | 15.68 | 14.58 | 14.85 | 20.54 | 20.56 | ||
| Task vector | MS COCO | MTV (NeurIPS24) | 28.41 | 32.67 | 34.21 | 34.11 | 35.72 | 13.02 | 13.74 | 15.26 | 13.18 | 16.72 |
| Category | ICL Training Dataset | Method | MS COCO | PICL | ||||||||
| 0-shot | 1-shot | 2-shot | 4-shot | 8-shot | 0-shot | 1-shot | 2-shot | 3-shot | 4-shot | |||
| Off-the-shelf | - | - | 11.02 | 14.87 | 16.55 | 21.11 | 22.34 | 22.31 | 26.94 | 22.17 | 30.88 | 31.42 |
| Retrieval and ordering | - | RICES (NeurIPS22) | 13.21 | 17.44 | 20.02 | 21.08 | 24.91 | 26.77 | 24.01 | 27.83 | 25.16 | 29.94 |
| VICL (ACL24) | 12.88 | 19.13 | 20.76 | 22.05 | 24.77 | 20.42 | 29.63 | 28.91 | 28.04 | 32.11 | ||
| MMICES (WACV25) | 10.74 | 15.62 | 18.03 | 20.14 | 23.09 | 21.55 | 27.48 | 18.92 | 25.77 | 27.61 | ||
| Task vector | MS COCO | MTV (NeurIPS24) | 6.11 | 10.84 | 14.73 | 17.02 | 20.88 | 24.41 | 22.88 | 18.72 | 28.11 | 30.92 |
| Category | ICL Training Dataset | Method | MS COCO | PICL | ||||||||
| 0-shot | 1-shot | 2-shot | 4-shot | 8-shot | 0-shot | 1-shot | 2-shot | 3-shot | 4-shot | |||
| Off-the-shelf | - | Random | 26.41 | 35.02 | 35.11 | 32.84 | 35.91 | 24.82 | 17.77 | 28.66 | 22.48 | 29.14 |
| Retrieval and ordering | - | RICES (NeurIPS22) | 24.91 | 32.66 | 36.58 | 34.11 | 31.94 | 26.04 | 28.85 | 25.71 | 34.72 | 30.63 |
| VICL (ACL24) | 23.84 | 36.02 | 36.44 | 35.97 | 34.82 | 22.51 | 19.47 | 27.18 | 31.11 | 33.62 | ||
| MMICES (WACV25) | 28.73 | 30.42 | 34.95 | 36.48 | 37.28 | 19.18 | 15.77 | 21.42 | 29.83 | 34.66 | ||
| Task vector | MS COCO | MTV (NeurIPS24) | 22.74 | 34.18 | 29.41 | 33.02 | 35.88 | 21.92 | 18.74 | 30.11 | 23.84 | 31.27 |
| Contrastive Benchmark | TrueMICL | MS COCO | ||||||||
| 0-shot | 1-shot | 2-shot | 4-shot | 8-shot | 0-shot | 1-shot | 2-shot | 4-shot | 8-shot | |
| Winoground | 28.74 | 48.12 | 52.03 | 64.91 | 66.77 | 36.84 | 41.72 | 43.03 | 42.11 | 43.88 |
| VisMin | 28.74 | 49.72 | 54.18 | 60.05 | 65.11 | 40.07 | 44.82 | 44.44 | 45.11 | 43.96 |
| InpaintCOCO | 31.11 | 49.63 | 54.62 | 63.80 | 68.24 | 38.21 | 45.02 | 45.18 | 43.77 | 46.91 |
| EqBen | 27.41 | 52.88 | 53.03 | 59.44 | 63.02 | 38.72 | 47.03 | 41.92 | 48.21 | 41.33 |
| Category | Method | PICL | TrueMICL | ||||
| 2-shot | 3-shot | 4-shot | 2-shot | 4-shot | 8-shot | ||
| Off-the-shelf | - | ||||||
| Retrieval & Ordering | RICES | ||||||
| VICL | |||||||
| MMICES | |||||||
| Task Vector | MTV | ||||||
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Multimodal ICL
Multimodal in-context learning (ICL) studies how models use examples and other context to solve tasks involving images, text, audio, and video.
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