A Language Prior Based Focal Loss for Visual Question Answering

According to current research, one of the major challenges in Visual Question Answering (VQA) models is the overdependence on language priors (and neglect of the visual modality). VQA models tend to predict answers only based on superficial correlations between the first few words in question and frequency of related answer candidates. To address this issue, we propose a novel Language Prior based Focal Loss (LP-Focal Loss) by rescaling the standard cross entropy loss. Specifically, we employ a question-only branch to capture the language biases for each answer candidate based on the corresponding question input. Then, the LP-Focal Loss dynamically assigns lower weights to biased answers when computing the training loss, thereby reducing the contribution of more-biased instances in the train split. Extensive experiments show that the LP-Focal Loss can be generally applied to common baseline VQA models, and achieves significantly better performance on the VQA-CP v2 dataset, with an overall 18% accuracy boost over benchmark models.