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Like People, Bees Can Be Fooled by False Memories

Bumblebees gravitate toward unfamiliar flowers that merge two patterns they know—a classic error of long term memory

(Jef Meul/NiS/Minden Pictures/Corbis)
smithsonian.com

Memory is a notoriously slippery ally. It’s alarmingly easy to purposely distort recall, even in people with the unusual ability to remember minute details, going back to childhood. Absent manipulation, it is still extraordinarily difficult to be a reliable witness. Studying faults in memory, though, can reveal how it functions—even in such seemingly simple organisms as bees.

The latest work, published in Current Biology, looks at how bees, like humans, can be prone to false memories. Previously, researchers had manipulated the electrical zings of specific mouse brain cells to give rodents a false memory of an event that never happened. But naturally occurring false memory hasn’t been shown in non-humans before. 

Honeybees and bumblebees are favorite subjects in the study of learning and memory because they rely on color, scent and taste to help them find flowers and, therefore, food. They forage, so they are also good at using sensory cues to map their surroundings. In the new study, U.K.-based researchers tested bumblebees’ false memory formation using differently colored fake flowers.

The researchers first trained their bees (Bombus terrestris) to know which flowers contained a droplet of nectar. All the bees learned that two types of flowers contained a reward: For example, for one group tested, the flowers worth visiting were solid yellow ones and flashy ones sporting alternating rings of black and white. (Other bee groups learned different patterns, such as a black grid over white, to avoid any sort of innate bee preferences that might obscure the results.) Then, the researchers gave the insects a chance to choose from a wide array of different flowers. 

Right after they had been trained, the bees knew exactly which flowers to visit—the solid yellow and the black and white ones. But when they were tested three days later, they started to gravitate toward a third type of flower that hadn’t been present during training.

This flower represented a merged version of the two they had been trained to recognize. For our example group, yellow and white concentric circles now seemed most exciting. As the experimental trials proceeded on that third day, the bees apparently got more and more mixed up: Just 34 percent preferred the merged blooms during the first ten trials, but 50 percent did during the last ten. These bees seemed convinced that the hybrid fake flower was the one they remembered carrying nectar.

The preference change shows that bumblebees are vulnerable to a memory error that also crops up in people, the researchers write. Research in humans shows that we make similar merging mistakes when asked to recall faces, nonsense words and simple sentences. 

Since the bees and humans do fine with tests right after training, the problem isn’t with short term memory, but when the memory is moved into long term storage. During that move, information is lost and details glossed over. (The "mind palace" that Sherlock Holmes uses is a strategy that to try and avoid just that.)

This tendency to come up with false, merged memories isn’t a bad thing, though. It’s proof that our memory system is flexible. "There is no question that the ability to extract patterns and commonalities between different events in our environment [is] adaptive," Lars Chittka of Queen Mary University of London says in a press release. "Indeed, the ability to memorize the overarching principles of a number of different events might help us respond in new situations. But these abilities might come at the expense of remembering every detail correctly." His team has also found that people who are good at learning to classify objects are particularly susceptible to this kind of memory glitch.

It’s probably good for bees (and other creatures) to make these kind of "mistakes" because they’re likely to at least investigate objects or locations they’ve never seen before. If it is anything like something they do remember seeing, it might worth checking out. After all, unfamiliar flowers carry nectar, too.

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