By Dr. Ken Broda-Bahm:
Witnesses make mistakes. And for the adversary, those mistakes can make for useful and entertaining cross-examination. We expect that to occur with fact witnesses who might be naive to the legal process and the attorney's goals, but is there less opportunity to pounce on those mistakes when examining an expert? New research suggests that, in contrast, there might even be greater opportunity. The study (Greene, 2016) finds that subject-area experts are more rather than less likely to make mistakes about their specialty. Indeed, knowing a great deal about a subject doubles the risk of false memories about that subject. As reported in a review in Telegraph, researcher Ciara Greene from University College Dublin, looked at 489 subjects who were measured based on their interest in a number of topics (like politics, science, and sports) as well as their knowledge in those topics. Then they were given a list of four events, three of which were true and one of which was fictional. Having a high level of interest or knowledge in an area increased the chances of true memories, as we would expect, but increased the chances of false memories as well. One fourth of those responding reported a false memory within their area of greatest interest, and those who had significantly greater knowledge on a topic were nearly twice as likely to remember incidents about that topic that never happened. As Ciara Greene noted in LiveScience, "Most people are pretty confident in their own memory for events, but this research shows that false memory is a lot more frequent than many people realize."
Social scientists have long been aware that false memories are common. But why would it be the case that expertise, in the form of greater knowledge and interest in an area, would correlate with more rather than fewer false memories? The author theorizes that such false-positives are the result of greater familiarity. In other words, new information, whether true or false, has a better chance of feeling familiar to the expert because it relates in some way to something that is already known. As the author told LiveScience, "This can result in a sense of familiarity or recognition of the new material, leading to the conviction that the information has been encountered before and is in fact an existing memory." More knowledge means more possible connections and more possible mistakes. All of that means that experts are prone to error too, possibly more so.