Bumblebees can be muddled by false memories, study finds

Ciaran Burke

Bumblebees can be muddled by false memories in the same way as humans, a study has found.

It is the first time the phenomenon has been demonstrated in a non-human species.

The fact that it can affect an insect suggests that distorted or fabricated memory is not just a problem for police investigations but widespread throughout the animal kingdom.

Lead scientist Dr Lars Chittka, from Queen Mary, University of London, said: "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.

"Stimuli that have actually never been viewed before, but are a combination of the features presented in training, are chosen during memory recall."

Bumblebees may be blessed with tiny brains but they have good memories. Not only do they remember the patterns, colours and scents of various kinds of flower, but they can navigate to the blooms over long distances and find their way home again.

For the study, the first to investigate false memories in non-humans, Dr Chittka's team first trained bumblebees to expect a sweet reward when visiting artificial flowers in a particular sequence.

One group of bees learned to go to a yellow flower first, followed by one marked with black and white rings. Another group was trained to visit the flowers in the opposite order.

In subsequent tests, the same bees were given a choice between those flowers and a third type with yellow and white rings, representing a mixed up version of the two they had seen before.

At first, the bees were not fooled by the addition of the yellow striped flowers and continued to prefer the flower that most recently rewarded them during training - either yellow or black and white.

Between one and three days later, however, confusion set in. Half the time the bees selected the flower with yellow and white stripes, even though it had not formed part of their training.

Their long term memories of being rewarded by different kinds of flower had "merged together", said the researchers, whose findings are reported in the journal Current Biology.

The bees' behaviour mirrored that of humans experiencing memory errors, they pointed out. Rather than exposing a "bug" in the memory system, it was a side effect of a quite sophisticated adaptive recall mechanism.

The same team has recently found that people who are particularly good at learning rules to classify objects are also prone to false memories.

Dr Chittka said: "There is no question that the ability to extract patterns and commonalities between different events in our environment is adaptive.

"Indeed, the ability to memorise 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."

With their limited brain capacity, bees might find the pressure to "economise" by storing general features of a class of objects rather than details of each individual object to be even more intense, he added.

The researchers are now using radar tracking to follow bees and their flower choices over the whole of their lives.