Towards Grounded Visual Spatial Reasoning in Multi-Modal Vision Language Models

With pre-training of vision-and-language models (VLMs) on large-scale datasets of image-text pairs, several recent works showed that these pre-trained models lack fine-grained understanding, such as the ability to count and recognize verbs, attributes, or relationships. The focus of this work is to study the ability of these models to understand spatial relations. Previously, this has been tackled using image-text matching (e.g., Visual Spatial Reasoning benchmark) or visual question answering (e.g., GQA or VQAv2), both showing poor performance and a large gap compared to human performance. In this work, we use explainability tools to understand the causes of poor performance better and present an alternative fine-grained, compositional approach for ranking spatial clauses. We combine the evidence from grounding noun phrases corresponding to objects and their locations to compute the final rank of the spatial clause. We demonstrate the approach on representative VLMs (such as LXMERT, GPV, and MDETR) and compare and highlight their abilities to reason about spatial relationships.