"What happens when people witness an event, say, a crime or accident, and are later exposed to new information about the event? Two decades of research have been devoted to the influence of new information on the recollections of such witnesses. An all-too-common finding is that after receipt of new information that is misleading in some way, people make errors when they report what they saw. New, post-event information often becomes incorporated into a recollection, supplementing or altering it, sometimes in dramatic ways. New information invades us, like a Trojan horse, precisely because we do not detect its influence. Understanding how we become tricked by revised data about a witnessed event is a central goal of this research. Current research showing how memory can become skewed when people assimilate new data utilizes a simple paradigm. Participants first witness a complex event, such as a simulated violent crime or automobile accident. Subsequently, half the participants receive new, misleading information about the event. The other half do not get any misinformation. Finally, all participants attempt to recall the original event. In a typical example of a study using this paradigm, participants saw a simulated traffic accident. They then received written information about the accident, but some people were misled about what they saw. A stop sign, for instance, was referred to as a yield sign. When asked whether they originally saw a stop or a yield sign, participants given the phony information tended to adopt it as their memory; they said they saw a yield sign. In these and many other experiments, people who had not received the phony information had much more accurate memories. In some experiments, the deficits in memory performance following receipt of misinformation have been dramatic, with performance differences as large as 30% or 40%."