Even bumblebees ‘merge’ their memories
Bumblebees are just as guilty of merging memories as NBC anchor Brian Williams, it turns out.
A new study, published online Thursday in the journal Current Biology, suggests that Bombus terrestris is prone to a type of memory error common among humans -- melding information from two episodes into one.
Bees may not be able to tell tales about being under fire in flights over Iraq, but they do demonstrate remarkable memory ability. And because they have a mere 960,000 neurons compared with the human complement of about 85 billion, they probably need to economize on storage and processing.
That’s what makes them valuable models to researchers trying to find the roots of complex brain functions in the simpler structures preserved across species over many millions of years of evolution. After all, many studies have demonstrated that memory is formed on a cell-by-cell basis.
Lars Chittka, a behavioral ecologist at Queen Mary University, London, has been probing the limits of bees’ memories in the lab. He and colleague Kathryn Hunt were curious about how bumble bees processed episodic memory. So they trained bees to respond to rewards doled out by artificial flowers: one yellow, another with black and white concentric circles.
Afterward, the bees were given three choices -- the same flowers on which they were trained and a third that merged characteristics of both.
Not surprisingly, bees tested soon after the trials tended to remember the last reward (the order of the test flowers was swapped between groups). So, if a bee was trained on yellow most recently, the bee flew to the yellow flower at rates far higher (77%-79%) than would be explained by chance alone.
But as time went on, the bees started showing a greater propensity to choose the hybrid flower -- yellow concentric rings, for example.
The researchers added complicated choices and varied colors and combinations, testing whether bees were just generalizing for such factors as “yellowness,” whether certain patterns were inherently more attractive, and whether memory and learning were stronger for certain colors or patterns.
The result that stood out most was that bees seemed to prefer a merged stimulus over the long haul. Their long-term memory, in other words, seemed to meld two separate events.
“Such memory errors are quite well established in humans,” Chittka said. “We tend to think that our memory is, in general, accurate, and where it’s inaccurate we have a perception that it just fades and we might have forgotten something. But there is a quite a lot of complete mis-remembering, merging, mixing things up. In the courtroom this can have serious consequences.”
Beyond sinking a career, such errors can prove deadly. So, it’s a bit of a stretch to think that evolution would have selected for the trait, Chittka said.
“But it’s very possible that these errors are a byproduct of useful memory processes,” he said.
Extracting common elements from various episodes helps us learn rules that govern our environment, preparing us for similar experiences. That ability is fundamental to higher cognition, in fact.
“In itself such rule-learning isn’t wrong,” Chittka said. “It just produces errors when it’s applied too generally.”
Psychologists theorize that “conjunction errors” occur on retrieval, not in the formation of episodic memory.
So Williams’ brain might have made a useful, space-saving shortcut to “remind” him that traveling in a helicopter in a war zone can get you shot down. It just didn’t happen in one episode.
Or Williams could just be lying.
I won’t lie: I’m not a scientist. But follow me on Twitter anyway: @LATsciguy
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