Mind the Uncertainty in Human Disagreement: Evaluating Discrepancies Between Model Predictions and Human Responses in VQA

Jian Lan, Diego Frassinelli, Barbara Plank

Abstract: Large vision-language models struggle to accurately predict responses provided by multiple human annotators, particularly when those responses exhibit high uncertainty. In this study, we focus on a Visual Question Answering (VQA) task and comprehensively evaluate how well the output of the state-of-the-art vision-language model correlates with the distribution of human responses. To do so, we categorize our samples based on their levels (low, medium, high) of human uncertainty in disagreement (HUD) and employ, not only accuracy, but also three new human-correlated metrics for the first time in VQA, to investigate the impact of HUD. We also verify the effect of common calibration and human calibration (Baan et al. 2022) on the alignment of models and humans. Our results show that even BEiT3, currently the best model for this task, struggles to capture the multi-label distribution inherent in diverse human responses. Additionally, we observe that the commonly used accuracy-oriented calibration technique adversely affects BEiT3’s ability to capture HUD, further widening the gap between model predictions and human distributions. In contrast, we show the benefits of calibrating models towards human distributions for VQA, to better align model confidence with human uncertainty. Our findings highlight that for VQA, the alignment between human responses and model predictions is understudied and is an important target for future studies.