  Humans refer to objects in their environments all the time, especially in
dialogue with other people. We explore generating and comprehending natural
language referring expressions for objects in images. In particular, we focus
on incorporating better measures of visual context into referring expression
models and find that visual comparison to other objects within an image helps
improve performance significantly. We also develop methods to tie the language
generation process together, so that we generate expressions for all objects of
a particular category jointly. Evaluation on three recent datasets - RefCOCO,
RefCOCO+, and RefCOCOg, shows the advantages of our methods for both referring
expression generation and comprehension.
