Visual Haystacks: A Vision-Centric Needle-In-A-Haystack Benchmark

Rebuttal by Authors

We appreciate the reviewer for providing thoughtful feedback and for highlighting our paper’s contributions, including the creation of a novel and insightful benchmark dataset and the development of the MIRAGE framework. Below, we respond to each of the concerns: **[W1, W2] Limited Question Types and Templates** Our VHs benchmark is intentionally designed with binary questions and simple templates. The rationale is to isolate and evaluate basic skills, visual retrieval and basic cross-image reasoning, without introducing confounding factors, like reasoning the logic in questions. By keeping the tasks straightforward, we provide a diagnostic unit test allowing researchers to pinpoint whether deficiencies lie in visual retrieval or reasoning. While more complex and diverse question templates are valuable for simulating real-world scenarios, they can obscure the diagnostic clarity of model performance. While expanding VHs to include richer templates is a logical next step, our results show that current LMMs struggle with even this simple test, so we strongly believe that such an expansion is out of scope for this initial effort. This point was briefly mentioned in L150-155 and Appendix D of our submission and further clarified in Appendix D of the updated paper. **[W3] Performance Drop in General VQA Tasks** We would like to emphasize that the primary focus of this paper is on large-scale multi-image QA tasks, where MIRAGE achieves SOTA results on the VHs benchmark (a unit test for these capabilities) and a real-world benchmark dataset, RetVQA, among all open-source solutions. While MIRAGE shows slightly reduced performance on some single-image QA tasks as detailed in Table 1, its main advantages are: 1. **Scalability**: MIRAGE is the only framework capable of processing thousands of images in a single query, greatly surpassing the input capacity of both proprietary and open-source models. 2. **Performance**: MIRAGE excels in multi-image tasks and, despite a slight drop in some single-image tasks like TextVQA, it outperforms LLaVA-v1.5-7B in some others like MMB(-CN), and rivals proprietary models in some cases. 3. **Efficiency**: MIRAGE achieves an 18x token compression and gets faster runtime in Table 6 (B). While this may slightly impact single-image QA performance, it is a strategic trade-off that enables MIRAGE to excel in large-scale multi-image tasks. This clarification was added to Section 5 of the updated paper. **[W4] MIRAGE’s Visual-RAG Approach** While MIRAGE functions as a visual-RAG framework with a retriever and an LMM, it is an end-to-end trained "single-model architecture," as detailed in Section 4.1 and Figure 5(A) of the submission paper. Thus, the "retriever" in this context should be understood as a component that primarily de-selects irrelevant details to enhance long-context reasoning. Based on this, we believe that our comparison with other “single-model LMMs” on VHs is both fair and valid. We have addressed this further in L310-318 of the updated paper. To assess the efficacy of the de-selection component, we compare the retrieval accuracy between MIRAGE and CLIP in Figure 6(A) and the QA accuracy between MIRAGE and CLIP+LLaVA in Table C.2 of the original submission (updated to Table C.3). These results highlight that such naive combinations fall short of optimal performance, emphasizing the significance of MIRAGE’s architecture. **[W5] Real-World Relevance of the VHs Benchmark** While the VHs benchmark serves as a diagnostic unit test (as mentioned in [W1]) and may not fully replicate real-world scenarios, we argue that the ability to find images containing specific objects is a foundational skill essential for various large-scale multi-image reasoning applications. These include searching for objects of interest in personal photo albums, identifying patterns in medical image databases, monitoring deforestation using satellite imagery, mapping urban changes with autonomous navigation data, and understanding consumer behavior through retail surveillance footage. This argument is addressed in the updated Lines 33–39 of the submission paper. We are happy to have further discussion if the reviewer could suggest specific tasks or datasets that represent real-world long-context challenges. **[Q1] Clarification on MIRAGE and Q-Former (Table 1 and 2)** To clarify, the implementation of Q-former is consistent across both tables and MIRAGE does utilize Q-former for image token compression. Table 1 reflects the full MIRAGE framework's performance, incorporating the Q-former compressor, a retriever module, and the Llama-v3.1 LLM. In contrast, Table 2 in the original submission (Table C.2 in the updated paper) presents an ablation study focused on Q-former's effectiveness in a simpler setup using LLaVA-v1.5 (lmsys/vicuna-v1.5-7b) without the retriever. Adjustments have been made to the paper to clarify these distinctions.

Rebuttal by Authors

We appreciate the reviewer for providing valuable comments and for highlighting our strengths in developing a meaningful visual NIAH benchmark, uncovering interesting findings when evaluating LMMs, and providing rigorous experiments. Below, we address each of the concerns: **[W1] Focus on Recognition Tasks** We want to clarify that object recognition—retrieving key visual content from a large collection of data—is a key skill for real-world long-context visual understanding tasks like searching through photo albums or analyzing medical and satellite imagery. Just as the NIAH benchmark (easily solvable with regex) serves as a basic unit test for LMMs, VHs—despite potentially being solvable with an object detector as shown in Figure 2 and 3 of the submission—can also act as a diagnostic tool for LMMs. Additionally, VHs assess cross-image reasoning, where LMMs often show significant performance declines when integrating information across multiple images, as detailed in Figure 3(A) and Appendix C.4. These points were briefly discussed in Appendix D of the submission and have been elaborated upon in the updated paper. **[W2] Multi-Needle Challenges and Dataset Design** We acknowledge that performance on the multi-needle track sometimes surpasses the single-needle one for image sets larger than 20. We'd like to clarify that the performance on the multi-needle track is not necessarily lower than that of the single-needle track. The multi-needle track poses questions in the format: "Q: For all images with <anchor object>, do ALL/ANY of them contain <target object>? A: Yes/No." We can then categorize each data point into two cases: 1. The ANY-Yes/ALL-No QA pairs: These cases are easier in the multi-needle track since retrieving at least one correct image can suffice. Conversely, the single-needle task demands precise retrieval, posing a greater challenge for models prone to false negatives. 2. The ANY-No/ALL-Yes QA pairs: These are more difficult in the multi-needle track than the single-needle one, as the model must retrieve all relevant images and integrate their information, demanding stronger cross-image reasoning. The results in Figure C.3 of the updated paper support the above explanation, showing that the benchmark effectively reveals nuanced model behaviors rather than indicating a design flaw. We have included this discussion in Appendix C.4. **[W3] Relevance of the Retriever Module** We believe that the retriever-LMM collaboration in our MIRAGE framework is well-motivated and is not ad-hoc in design. 1. Retriever: As there can be a lot of irrelevant visual content in the input, a retriever, filtering images based on relevance before reasoning occurs in the LMM, can make the whole system more efficient in terms of runtime (See Figure 6 (B) of the submission paper) and prevent the LMMs suffering from visual distractors – a limitation for current LMMs nowadays as shown in Figure 1 of the submission paper. 2. LMM: Given a small number of images, LMMs can be a fundamental and critical processor for the visual reasoning and next token prediction task for the actual answer generation. This framework makes MIRAGE robust for both the VHs unit tests and realistic large-scale multi-image QA tasks. These points were briefly addressed in Section 4.1 of the submission and further emphasized in L310-318 in the updated paper. **[W4] Performance on Other Benchmarks** The primary focus of the paper is on basic capabilities—visual retrieval and basic cross-image reasoning—for large-scale multi-image QA. MIRAGE achieves SOTA results on the VHs benchmark (a unit test for these capabilities) and on the existing RetVQA dataset among all open-source solutions, indicating its superiority in multi-image QA. In addition to the main focus, we've included seven common single-image QA benchmarks as a bonus. On them, MIRAGE performs on par with existing solutions as shown in Table 1. Updates for MME and SEED-Bench are also reflected in Table 1. For CHAIR [1], noted as a metric for hallucination detection, we have included an advanced hallucination benchmark POPE in Table 1 of the submission. [1] Rohrbach, Anna, et al. "Object hallucination in image captioning." EMNLP 2018. **[Q2] Analyses on Failure Cases** We have added an analysis of failure cases for Gemini v1.5 and GPT-4o in Figure C.2 of the updated paper. In summary, these models tend to struggle with small and non-salient objects due to the lack of a filtering module. **[Q3] Code Licensing Issues** Both the MIT and Apache 2.0 licenses are permissive and compatible with one another (i.e. neither is a copy-left license or restricts wide release). We plan to release our code under the MIT license and retain Apache 2.0 for any code originally licensed by LLaVA. The LLaVA LICENSE file was included in our anonymous repository to comply with Apache 2.0. We appreciate the reviewer's concern and are open to discussing any specific issues further.

Rebuttal by Authors

We appreciate the reviewer for highlighting our paper’s contributions, including the construction of a novel benchmark dataset, the rigorous evaluation of various LMMs, and the development of an innovative visual-RAG framework. Below, we address each of the concerns: **[W1, W2, Q1] Limited Object and Question Diversity** While we understand that some of the questions are simple to human users, the primary objective of the Visual Haystacks (VHs) benchmark is to serve as a fundamental unit test for assessing LMMs' multi-image processing capabilities. As noted in L150-155 of both the submission paper and the updated paper, we deliberately constructed the dataset using COCO objects and straightforward (one for the single-needle track and two for the multi-needle track) templates to isolate and evaluate core retrieval and reasoning skills without additional confounding variables (such as out of domain data, as it is likely that most models are highly familiar with COCO objects). While we believe that expanding the object and question diversity is important (such as adding an open object set, adding questions that reason over actions and attributes, exploring multiple languages, or adding multi-step inference questions), our results presented in this paper demonstrate that models struggle with even this simple test, so we strongly believe that such an expansion is out of scope for this initial effort. We hope to consider such expansions for the following versions of the benchmark. These limitations and future direction are included in Appendix D of the paper, for both the updated version and the submission version. **[W3] More like Object Detection than QA Reasoning** We would like to clarify that detection—retrieving key information from a large collection of data—is a fundamental skill for enabling real-world long-context visual understanding tasks, like searching through photo albums or analyzing medical and satellite imagery in large databases. Just as the NIAH benchmark (easily solvable with regex) serves as a basic unit test for LLMs in long-context NLP tasks, we believe VHs offers a similarly essential unit test for evaluating LMMs in long-context visual understanding. While VHs could theoretically be addressed using an object detector (which we have already included as a baseline in Figure 2 and 3 of the submission), they represent a useful diagnostic tool/unit test for assessing these models as mentioned above. This point was briefly mentioned in L30-L50 and Appendix D of our submission and further clarified in Appendix D of the updated paper. Also, it's important to emphasize that our dataset is not solely focused on detection. It also includes a basic assessment of cross-image reasoning. In Figure 3 (A) of the submission paper and the updated Appendix C.4, we observe that LMMs experience significant performance degradation in the multi-needle track compared to the single-needle track, where models must integrate information across multiple images. As previously mentioned, VHs is designed to diagnose LMMs on two basic capabilities—visual retrieval and reasoning. We believe that expanding the scope of the benchmark, while valuable future work, is beyond the scope of this current contribution. **[W4] Missing Related Work** We thank the reviewer for pointing out these relevant contemporary works. We've adjusted the related work section to add these. **[Q2] The advantages of VHs over existing multi-image benchmarks** VHs offers two main advantages over existing multi-image benchmark datasets: 1. **Simplicity**: VHs is specifically designed to evaluate LMMs’ capabilities in visual retrieval and basic cross-image reasoning without introducing additional confounding factors, such as out-of-distribution images or complex language reasoning. By maintaining this simplicity, VHs serves as a diagnostic tool for LMMs, where the single-needle track focuses on visual retrieval performance, and the multi-needle track evaluates basic cross-image reasoning. In contrast, existing multi-image benchmarks often aim to address domain-specific or real-world applications, making the questions inherently more complex. While this complexity may reflect harder real-world challenges, it can make diagnosing specific LMM abilities difficult, as answering a single question often requires multiple intermixed capabilities. 2. **Scale**: Existing multi-image benchmarks like RETVQA include fewer than 30 images per question. The three datasets mentioned by the reviewer contain even fewer images, with fewer than 10 images per question. In comparison, VHs scales up to 10K images per question, far exceeding the size of existing benchmarks. This large-scale setting better mirrors real-world large-scale multi-image QA tasks, like photo album searching or analyzing medical and satellite imagery in large databases. We have clarified these points in the related work section of the updated paper. Thank you again for raising this issue.