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A new study attempts to measure how knowledge gleaned from Wikipedia may play out in one specific realm: the courts.

A team of researchers led by Neil Thompson, a research scientist at MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL), recently came up with a friendly experiment: creating new legal Wikipedia articles to examine how they affect the legal decisions of judges. They set off by developing over 150 new Wikipedia articles on Irish Supreme Court decisions, written by law students. Half of these were randomly chosen to be uploaded online, where they could be used by judges, clerks, lawyers, and so on — the “treatment” group. The other half were kept offline, and this second group of cases provided the counterfactual basis of what would happen to a case absent a Wikipedia article about it (the “control”). They then looked at two measures: whether the cases were more likely to be cited as precedents by subsequent judicial decisions, and whether the argumentation in court judgments echoed the linguistic content of the new Wikipedia pages.

It turned out the published articles tipped the scales: Getting a public Wikipedia article increased a case’s citations by more than 20 percent. The increase was statistically significant, and the effect was particularly strong for cases that supported the argument the citing judge was making in their decision (but not the converse). Unsurprisingly, the increase was bigger for citations by lower courts — the High Court — and mostly absent for citations by appellate courts — the Supreme Court and Court of Appeal. The researchers suspect this is showing that Wikipedia is used more by judges or clerks who have a heavier workload, for whom the convenience of Wikipedia offers a greater attraction.
“To our knowledge, this is the first randomized field experiment that investigates the influence of legal sources on judicial behavior. And because randomized experiments are the gold standard for this type of research, we know the effect we are seeing is causation, not just correlation,” says Thompson, the lead author of the study. “The fact that we wrote up all these cases, but the only ones that ended up on Wikipedia were those that won the proverbial ‘coin flip,’ allows us to show that Wikipedia is influencing both what judges cite and how they write up their decisions.”

“Our results also highlight an important public policy issue,” Thompson adds. “With a source that is as widely used as Wikipedia, we want to make sure we are building institutions to ensure that the information is of the highest quality. The finding that judges or their staffs are using Wikipedia is a much bigger worry if the information they find there isn’t reliable.”

The paper describing the study has been published in ” The Cambridge Handbook of Experimental Jurisprudence.”