by Suzanne Bouffard
Most of us can think of a time we forgot something important. But many people don’t realize that the opposite can happen: we sometimes create false memories of things that never occurred, even important things like whether we witnessed a crime. Although researchers have known about false memories for decades, cognitive neuroscientist David Gallo has been shedding light on why they happen; and on factors that may help prevent them.
“It used to be assumed that inaccurate memories happen because memory fades over time. That’s true, but there’s more to it,” according to Gallo. Our brains constantly try to make connections among things we are experiencing so that we can make sense of our world and solve problems. But that can also “generate misinformation that can later confuse us,” Gallo explains. This is why laboratory subjects who are asked to remember words from a list often falsely remember words that weren’t there but are similar to those that were.
The good news, according to Gallo’s research, is that the brain also has mechanisms built in to help us prevent false memories. When people are asked to remember pictures, the accuracy of their recall is dramatically better than when they are asked to remember text. Gallo has shown that this is true regardless of age, even for people in their 80’s. In fact, he finds, older adults are as accurate in remembering pictures as college students are; which is not the case with text.
It’s not just that pictures are inherently easier to remember than words, but that they activate different parts of the brain, according to studies Gallo has conducted with functional magnetic resonance imaging (fMRI). Picture memories are stored in regions at the back of the brain associated with vision, while text memories rely more heavily on the right prefrontal cortex (PFC), which is associated with analytical thinking. Because the PFC declines with age more rapidly than other regions, older adults are “more likely to distort information they read or heard.” The same is true of first graders, Gallo has found, likely because the visual part of their brains develops earlier than the PFC.
Gallo has also found that the accuracy of memories is affected by our strategies for remembering and our expectations. Like juries who have to consider the accuracy of a witness’ testimony, we judge the accuracy of our own memories, often subconsciously. We typically rely on our ability to recall vivid details, assuming that if we can’t picture such details, the event didn’t happen, says Gallo. But his studies suggest that people sometimes use another process of searching for circumstantial evidence that does or does not corroborate the memory, and that this process may also help to prevent false memories.
These findings may be able to illuminate whether and how much memories can be trusted, especially in high stakes situations like picking a criminal out of a line-up or testifying on the witness stand. The more distinctive the event, the more likely people are to remember it accurately, Gallo says, and whether they saw or heard it could affect the reliability of their recall. His research also suggests that detectives and lawyers can increase the accuracy of recall by explicitly prompting people for corroborating information such as what else they were doing and who was with them at the time of an event. There is no foolproof strategy for ensuring the accuracy of memories, Gallo concludes, but one thing is for sure: when it comes to memory, small factors can make a big difference.
David Gallo was recently honored with the Federation of Associations in Behavioral & Brain Sciences (FABBS) Foundation Early Career Investigator Award during the annual meeting of the Psychonomic Society.