Response to Reviewer ONXK (1/2)
Below, we respond to the points raised by Reviewer ONXK during the discussion period.
**Batch Size. “With only a brief experiment provided in Q5, I am not convinced that RaVL outperforms other baselines across various batch sizes. The impact of batch size is not a trivial factor.”**
In our paper, we used a batch size of 128 across all mitigation experiments (Section 4). We selected a batch size of 128 for the following reasons. First, a batch size of 128 is the largest size that will fit on a single A100 GPU; we specifically used a single A100 GPU for all experiments in order to demonstrate the ease of use and cost-effectiveness of RaVL. Second, a batch size of 128 is either larger or equivalent to the batch sizes used by prior works that fine-tune VLMs for real-world applications (e.g. medical settings [1,2]) demonstrating that our choice of the batch size hyperparameter is consistent with real-world practice. Third, the Spurious-Aware Mitigation baseline, which is the only other previously-developed approach for the fine-tuned VLM setting (Appendix A), is designed to operate with a batch size of 128; consequently, using a batch size of 128 across evaluations enables a fair comparison with this baseline. As shown in Table 3 in the paper, RaVL Stage 2 outperforms all mitigation baselines.
Beyond the batch size justification shared above, to be further responsive to the provided reviewer comment, we extend the batch size ablations provided with our original rebuttal by evaluating RaVL across three batch sizes (32, 128, and 256) and six baselines. We evaluate multiple COCO evaluation settings for each ablation. Across a total of 72 trained VLMs $M_{new}$ evaluated in the tables below, **we show that RaVL outperforms all baselines across all evaluated batch sizes**. We thank the reviewer for this suggestion, and we will be sure to update the manuscript with this ablation.
| Batch Size | Method | Img. Overall | Img. Worst Group | Reg. Overall | Reg. Worst Group|
|----------------------|------------------|------------------|------------------|------------------|------------------|
| 32 | Standard FT | 59.1 | 25.2 | 69.3 |44.1 |
| 32 | Upsampled FT | 60.3 | 28.0 | 65.2 | 34.3 |
| 32 | VL-ERM |58.4 |21.6 | 67.7 | 37.2 |
| 32 | VL-GDRO | 59.6 |24.3 | 69.3 | 35.2 |
| 32 | Spurious-Aware |54.2 |12.2 | 66.9 | 36.2 |
| 32 | RaVL (Ours) | **64.3**| **39.7**| **75.5** |**44.7**|
| Batch Size | Method | Img. Overall | Img. Worst Group | Reg. Overall | Reg. Worst Group|
|----------------------|------------------|------------------|------------------|------------------|------------------|
| 128 | Standard FT | 67.6 | 33.6 | 77.3 | 46.0 |
| 128 | Upsampled FT | 69.5 | 37.1 | 79.6 | 52.9 |
| 128 | VL-ERM | 68.2 | 29.0 | 78.1 | 46.3 |
| 128 | VL-GDRO | 69.7 | 31.5 | 77.5 | 44.6 |
| 128 | Spurious-Aware | 69.4 | 31.8 | 78.6 | 48.1 |
| 128 | RaVL (Ours) | **71.0** | **42.9** | **82.1** | **57.4**|
| Batch Size | Method | Img. Overall | Img. Worst Group | Reg. Overall | Reg. Worst Group|
|----------------------|------------------|------------------|------------------|------------------|------------------|
| 256 | Standard FT | 64.3 | 41.4 | 73.1 | 53.9 |
| 256 | Upsampled FT | 66.8 | 48.8 | 74.0 | 58.5 |
| 256 | VL-ERM | 62.5 | 24.9 | 73.2 | 44.9 |
| 256 | VL-GDRO | 63.5 | 29.8 | 75.2 | 45.1 |
| 256 | Spurious-Aware | 66.7 | 34.3 | 74.6 | 44.5 |
| 256 | RaVL (Ours) | **68.1** | **53.9** | **79.0** | **66.7**|
**Visualizations. “Thank you for including the additional qualitative experiment. However, I find the statement "The new VLM more precisely relies on core features" unclear. Could you please specify which core features you are referring to?”**
The images in the figure are obtained from the test set of a COCO evaluation setting in which the fine-tuned VLM $\mathcal{M}$ learned a strong spurious correlation between the class label "chairs" and the spurious feature "person". Visualizations show that before mitigation, the VLM is unable to precisely localize the core features associated with the class labels, often relying on the presence of people or various background details. After the RaVL mitigation procedure, the VLM $\mathcal{M}_{new}$ more precisely relies on core features (namely, the chairs).