Catching Gray Cygnets: an initial exploration

• Authors: Edwina L. Rissland;Xiaoxi Xu
• Venue: Proceedings of the 13th International Conference on Artificial Intelligence and Law
• Year: 2011

In this paper, we describe exploratory experiments for detecting potential "Gray Cygnet" cases that follow a known Black Swan. Gray Cygnets (GCs) are cases that are highly similar and subsequent to novel, surprising, provocative, exceptional cases, so-called Black Swans. They too are surprising, exceptional and provocative in the sense of continuing the change initiated by the Black Swan. Our experiments were carried out using a corpus of common law cases from the United States, particularly New York and Massachusetts, and the United Kingdom primarily in the era 1852-1916 during which there was dramatic change in the prevailing doctrine regarding recovery for damages by a remote buyer. It was provoked by the 1852 landmark case Thomas & Wife v. Winchester and elaborated in subsequent cases. Our methods use similarity measures from Case-Based Reasoning (CBR) based on classic claim lattice and nearest neighbor techniques. We also define and use "supreme on-point cases" (sopc's) that reside in the root node of a claim lattice. We define four simple tests to determine whether a problem case is a potential Gray Cygnet. The tests use the position of a known Black Swan in the analysis of a problem case, specifically whether it appears as a sopc, or mopc, and/or as a nearest neighbor. We also use the tests as an ensemble by using the decision of their majority vote. To evaluate the performance of our tests, we created an answer key based on a closed form definition of a GC in our domain.