Discover Novel Visual Categories From Dynamic Hierarchies Using Multimodal Attributes

Learning novel visual categories from observations and experiences in unexplored environment is a vitally important cognitive ability for human beings. A dynamic category hierarchy that is an inherent structure in a human mind is a key component for this ability. This paper develops a framework to build dynamic category hierarchy based on object attributes and a topic model. Since humans trend to utilize multimodal information to learn novel categories, we also develop an algorithm to learn multimodal object attributes from multimodal data. The new multimodal attributes can describe objects efficiently and can generalize from learned categories to novel ones. By comparison with a state-of-the-art unimodal attribute, the multimodal attributes can achieve 4%-19% improvements on average. We also develop a constrained topic model, which can accurately construct category hierarchies for large-scale categories. Based on them, the novel framework can effectively detect novel categories and relate them with known categories for further category learning. Extensive experiments are conducted using a public multimodal dataset, i.e., color and point cloud data, to evaluate the multimodal attributes and the dynamic category hierarchy. The experimental results show the effectiveness of multimodal attributes to describe objects and the satisfactory performance of the dynamic category hierarchy to discover novel categories. By comparison with state-of-the-art methods, the dynamic category hierarchy achieves 7% improvements.