Without any prior training, the bees flew more often to the empty card - thereby demonstrating that they understood that "zero" was a number less than the others, according to the study published Thursday (June 7) in the journal Science.
Their brains are about the size of a sesame seed, and they have fewer than one million neurons - compared with the 86,000 million that humans have.
It was thought that only humans, or species with similarly complex brains, could understand zero, which according to the researchers, is the backbone of modern mathematical and technological advancements.
"Zero is a hard concept to understand and a mathematical skill that doesn't come easily - it takes children a few years to learn", Adrian Dyer, an associate professor at RMIT University, Australia, and one of the authors behind the latest work, said in a statement.
Bees could be smarter than us in the understanding of "zero".
They learned to choose three elements when presented with three versus four, or two elements when presented with two versus three.
To put their hypothesis to test, they trained two groups of 10 bees to first understand the twin concepts of "less than" and "greater than" by rewarding each correct answer with sugar. And, when the surprise test, with a completely blank image or "empty set", was conducted for the first time, the bees already knew that it was at the lower end in a sequence of elements and made a decision to fly toward it.
"This is a tricky neuroscience problem", he said.
'It is relatively easy for neurons to respond to stimuli such as light or the presence of an object but how do we, or even an insect, understand what nothing is?
Dyer, a researcher in the Bio Inspired Digital Sensing-Lab (BIDS-Lab) in RMIT's Digital Ethnography Research Centre, said the findings opened the door to new understandings of how different brains could represent zero.
That said, as zero forms the core of maths and binary code, the researchers think that the neural model mechanics in bees could be used in the development of robotics and machine intelligence.
The researchers hope they can use the results to improve artificial intelligence. The bees were more accurate when zero was presented with a more distant number choice: a trait also seen in humans.
Previous researches revealed that animals with big brains like birds and monkeys grasp the idea of zero, and now, in the latest study, the scientists have shown that insects, particularly bees, are also included in that category.
"Their brains are probably processing information in a very clever [i.e., efficient] way" Dyer said.
A research team comprised of scientists in France and Australia were interested to learn what else, if anything, the insects could do, mathematically speaking. Large brains are thus not necessary to play with numbers.