Bumblebees, like humans, can also create false memories, researchers have found for the first time.
The new study is the first to explore false memories in any non-human animals, the researchers said. They now suspect that the phenomenon may be widespread in the animal kingdom.
"We discovered that the memory traces for two stimuli can merge, such that features acquired in distinct bouts of training are combined in the animal's mind," said Lars Chittka of Queen Mary University of London.
As a result, "stimuli that have actually never been viewed before, but are a combination of the features presented in training, are chosen during memory recall," said Chittka.
The bees can remember the patterns, colours, and scents of various kinds of flowers. They can also navigate to those flowers and back home again over long distances.
Most times when people have studied memory in animals, errors in performance have been taken to mean that the animals failed to learn the task or perhaps learned it and then forgot.
Chittka and his colleague Kathryn Hunt first trained bumblebees to expect a reward when visiting a solid yellow artificial flower followed by one with black-and-white rings or vice versa.
During subsequent tests, bees were given a choice between three types of flowers. Two were the yellow and the black-and-white types they had seen before.
The third type of flower had yellow-and-white rings, representing a mixed-up version of the other two.
Minutes after the training, the bees showed a clear preference for the flower that most recently rewarded them. Their short-term memory for the flowers was good.
One or three days later, however, something very different happened when the bumblebees' memory was put to the test.
At first, the bees showed the same preference displayed in the earlier tests, but as the day wore on, they appeared to grow confused.
Half of the time, they began selecting the flower with yellow rings, even though they had never actually seen that one in training before.
Chittka and Hunt said that the insects' observed merging of long-term memories is similar to the memory conjunction errors humans sometimes make.
They do not think those false memories in either bumblebees or humans are simply "bugs in the system," but rather are side effects of an adaptive memory system that is working rather well.
The research was published in the journal Current Biology.
