There's a scientific reason why you can remember exactly what you were doing on September 11. The traumatic nature of the event, partnered with the negative emotions it cues, enhances the memories triggered by its mention. It can be an unfortunate cycle: The more often you remember something, the better your memory of that thing becomes -- whether you care to remember it or not.
The human memory is a strange beast, and attempts to understand it often involve struggles to tame it. The results of a study published in the June issue of Psychological Science suggest that negative images enhance the ability to recall a memory. The results found their footing in a project initiated almost a year and a half ago by two Washington University scientists, Dr. Bridgid Finn and Dr. Henry L. Roediger III, who is also the university's dean of academic planning. The two tested Wash. U. students on their retention of Swahili vocabulary words after completing math problems, in what has to be the best way to spend your free time as an undergraduate ever.
When the students recalled a word's English equivalent correctly, a computer displayed one of three pictures: a blank screen, a neutral image (a bedspread, a spoon in a bowl) or a negative image (a gun pointed in your direction, a one-eyed cat). The scientists repeated the test ten times with 100 words, and capped the project with the equivalent of a final exam.
The results? The exposure to frightening or violent images helped students recall information.
"What we found is that those negative pictures do help to retrieve a memory and enhance it," Finn says. "They are negatively arousing. It's not just that you retrieve it, and it gets put back in, and that happens over and over again. Every time you retrieve a memory, you can change that information in some way."
Although the researchers published these results in June, they are already working on the project's follow-up. For the next step, the two flipped the study on its side by rewarding the wrong answers with images instead -- something they would never do in class, we bet. Students were still more likely to remember a correct answer on the final test if it had previously been paired with a negative image, even if they answered incorrectly.
"We're still finding the enhancing effect, and what that seems to suggest is that the retrieval itself is important in enhancing retention," Finn says. "When you give it a try and try to recall the item, that's when you get the enhancing effect. There seems to be something important about attempting to access that information and putting in the effort."
These results match those found in previous animal research on mice and crabs, but the length of the memory here is key. In the animal studies, long-term memory can mean days and weeks. In the human behavioral memory, it can be minutes. Does this enhancing effect persist in the extended long term?
"That's our next step," Finn says.