"The goal of memory is to leave you with a coherent story of what happened," says Mark Reinitz, a psychologist at the University of Puget Sound. And if the information is incomplete, he finds, the brain will do whatever it takes to assemble such a story— even generate false memories.
How did she fall? Your brain knows.
To explore this process, Reinitz and his colleague Sharon Hannigan showed 48 college students a series of slides depicting everyday activities containing one anomalous event, such as a trip to the supermarket in which the shopper passes a pile of fallen oranges. After 48 hours, the subjects saw the slides again, this time with an additional frame explaining how the event occurred— for instance, a photo showing a woman pulling an orange from the bottom of the stack. On second viewing, 68 percent of the students remembered seeing the explanatory image, even though it wasn't in the original sequence. This false memory, called causal-inference error, apparently results from the brain's efforts to find a cause to explain an observed effect. "Memory isn't just a record of external events but also a record of our interpretation of events," Reinitz says. Such mental tale-telling can be problematic in eyewitness testimony months after a crime.