Artificial intelligence “e-discovery” software can analyze documents in a fraction of the time for a fraction of the cost of the traditional platoon of lawyers and paralegals who work for months at high hourly rates.

E-discovery technologies generally fall into two broad categories that can be described as “linguistic” and “sociological.”  The most basic linguistic approach uses specific search words to find and sort relevant documents. More advanced programs filter documents through a large web of word and phrase definitions. A user who types “dog” will also find documents that mention “man’s best friend” and even the notion of a “walk.”

The sociological approach adds an inferential layer of analysis, mimicking the deductive powers of a human Sherlock Holmes.

Engineers and linguists at Cataphora, an information-sifting company based in Silicon Valley, have their software mine documents for the activities and interactions of people — who did what when, and who talks to whom. The software seeks to visualize chains of events. It identifies discussions that might have taken place across e-mail, instant messages and telephone calls.

The Cataphora software can also recognize the sentiment in an e-mail message — whether a person is positive or negative, or what the company calls “loud talking” — unusual emphasis that might give hints that a document is about a stressful situation. The software can also detect subtle changes in the style of an e-mail communication.

Automation of higher-level jobs is accelerating because of progress in computer science and linguistics. Mike Lynch, the founder of Autonomy, is convinced that “legal is a sector that will likely employ fewer, not more, people in the U.S. in the future.”

See how well you can do against the computer in a game of Rock-Paper-Scissors.