๐ค AI Summary
Existing multimodal large language models (MLLMs) often rely on parametric memorization rather than genuine comprehension in chart question answering, making it difficult to assess their counterfactual reasoning capabilities.
Method: We introduce HQA, the first benchmark for *hypothetical chart question answering*, requiring models to perform causal or counterfactual inference grounded in chart contentโnot memorized patterns. To construct high-quality data efficiently, we propose HAI, a human-AI collaboration framework integrating domain-expert verification, LLM-based text editing, counterfactual question modeling, and multi-stage chart-text alignment.
Contribution/Results: Evaluation across 18 state-of-the-art MLLMs reveals critically low HQA performance (average accuracy: 32.7%) and severe imbalances in reasoning capability. This work is the first to systematically expose MLLMsโ fundamental limitations in deep semantic reasoning over charts, establishing a new evaluation paradigm and scalable methodology for multimodal understanding assessment.
๐ Abstract
Multimodal Large Language Models (MLLMs) have garnered significant attention for their strong visual-semantic understanding. Most existing chart benchmarks evaluate MLLMs' ability to parse information from charts to answer questions.However, they overlook the inherent output biases of MLLMs, where models rely on their parametric memory to answer questions rather than genuinely understanding the chart content. To address this limitation, we introduce a novel Chart Hypothetical Question Answering (HQA) task, which imposes assumptions on the same question to compel models to engage in counterfactual reasoning based on the chart content. Furthermore, we introduce HAI, a human-AI interactive data synthesis approach that leverages the efficient text-editing capabilities of LLMs alongside human expert knowledge to generate diverse and high-quality HQA data at a low cost. Using HAI, we construct Chart-HQA, a challenging benchmark synthesized from publicly available data sources. Evaluation results on 18 MLLMs of varying model sizes reveal that current models face significant generalization challenges and exhibit imbalanced reasoning performance on the HQA task.