  Change captioning aims to describe the difference between a pair of similar
images. Its key challenge is how to learn a stable difference representation
under pseudo changes caused by viewpoint change. In this paper, we address this
by proposing a self-supervised cross-view representation reconstruction
(SCORER) network. Concretely, we first design a multi-head token-wise matching
to model relationships between cross-view features from similar/dissimilar
images. Then, by maximizing cross-view contrastive alignment of two similar
images, SCORER learns two view-invariant image representations in a
self-supervised way. Based on these, we reconstruct the representations of
unchanged objects by cross-attention, thus learning a stable difference
representation for caption generation. Further, we devise a cross-modal
backward reasoning to improve the quality of caption. This module reversely
models a ``hallucination'' representation with the caption and ``before''
representation. By pushing it closer to the ``after'' representation, we
enforce the caption to be informative about the difference in a self-supervised
manner. Extensive experiments show our method achieves the state-of-the-art
results on four datasets. The code is available at
https://github.com/tuyunbin/SCORER.
