The act of remembering may cause us to forget. So suggest the results of many an experiment which has demonstrated our retrieval of some facts from memory seems to prevent the recollection of other facts. However, a new study illustrates the power of reward to reverse that process. Researchers at Brown University discovered by giving volunteers a small prize, they could overcome "retrieval-induced forgetting" and remember what they likely would have forgotten on a simple memory test.

The Mysteries Of Memory

“Using our memories shapes our memories,” says Dr. Robert A. Bjork, a UCLA professor of cognitive psychology, who describes retrieval-induced forgetting (or RIF) in this way: “as we retrieve some information in response to cues, other things become inaccessible.”

An easy example of RIF, then, would be this: Say you are studying two separate categories of information, vegetables and sports. If you make an effort to learn some facts about broccoli (from the vegetable category), you will be worse at remembering facts about kale and other vegetables you didn’t study than you would be at remembering facts from the sports category you also didn’t bother to study. Neuroscientists believe this so-called "retrieval-induced forgetting" is actually a type of active mental filter that prevents us from becoming confused between data we've made an effort to learn and closely-related information we chose not to learn.

For a new study of memory, a team of Brown University neuroscientists performed an experiment with 91 student volunteers to understand whether or not reward influences RIF. They presented volunteers with some facts from two categories: fish and animals. Next, they asked the volunteers to practice only select fish facts. Then, the researchers asked the volunteers to identify both practiced and unpracticed fish category and animal category facts in a simple memory test.

However, the researchers had introduced a twist into this simple experiment. During the practice sessions, some but not all the volunteers received a small reward — sips of apple juice — whenever they completed their practice tasks successfully.

So what happened when all the volunteers, those rewarded and those not, were asked to remember information? After all, the phenomenon of RIF suggests the volunteers who practiced select fish facts would remember unpracticed animal category facts better than unpracticed fish category facts.

Surprisingly, the use of rewards erased RIF effects and improved volunteers recall of all the unpracticed facts in the fish category. In fact, reward group volunteers recalled unpracticed fish facts as well as unpracticed animal facts. Rewards, then, undermined RIF’s helpful filtering effect.

"Reward seems to activate anything, whether it is relevant or irrelevant,” said senior author Dr. Takeo Watanabe, a professor of cognitive, linguistic and psychological sciences at Brown.

Memory Storage Is Limitless, Memory Access Not So Much

Watanabe and his colleagues are not the only scientists to discover our brains function as complex, sometimes counter-intuitive recorders of data. “Whereas there’s no limit on storage, there does appear to be limits on the retrieval side [of memory],” says Bjork in a video he made for GoCognitive. Essentially, he and his co-researchers have demonstrated access to particular memories depends on certain “clues.” It is, in fact, particular “social clues, environmental clues, even body state clues,” which “select out what information is available and recallable of all this vast amount that’s in our long-term memories.”

Among his many experiments, Bjork tested student volunteers on information studied twice at intervals. One group studied the information two times in the same room, while another group studied two times in two separate rooms. All participants took a test in a new room. Those who studied in two separate rooms did better on the test than those who studied in the same room. More importantly, participants took the test in the same room where they had studied, they did better than when tested in a new room. Seemingly, the environmental cue contributed to retrieval strength of the information learned and enabled students to remember better.

Source: Imai H, Kim D, Sasaki Y, Watanabe T. Reward eliminates retrieval-induced forgetting. Proceedings of the National Academy of Sciences. 2014.