Reviews: Hierarchical Question-Image Co-Attention for Visual Question Answering

The paper presents an incremental contribution with respect to previous methods for VQA that only exploit an image attention mechanism guided by question data. Here, they also consider a question attention mechanism guided by image information. In this sense, the main hypothesis of this work is that jointly considering visual and question attention mechanisms can improve the performance of current VQA systems. I agree that this hypothesis can be relevant for the case of long questions, but I believe there is also a risk that question based attention guided by image information can be misleading, in the sense that usually an image includes several information sources, while the question is more focused. In Figure 3, authors include a graph that shows the impact of question length in performance, while this figure seems to show a tendency, the effect is still weak, maybe a numerical analysis can help to support this point. I believe, an analysis of potential differences (not only question length) between most common errors of previous works (only image attention) and the proposed approach (image and question attention) can help to support the relevance of the proposed attention mechanism.