If someone calls you a zero, you know it’s a diss without even having to think about it. You know right away that it means they think you’re nothing, smaller than any number. But humans aren’t the only ones who know what zero means. Scientists have found that chimps and monkeys, as well as Alex the African grey parrot, can grasp the abstract mathematical concept. And according to a study published this week in the journal Science, bees can understand what zero is, too.
In the new paper, a team of researchers led by Scarlett Howard, a Ph.D. candidate at Royal Melbourne Institute of Technology in Australia, outlined how they observed whether bees could demonstrate that zero is less than a number.
To do this, they tested bees’ understanding of a couple different numerical concepts before leading up to the big Z. First, they trained two groups of 10 bees to recognize either the concept of “less than” or “greater than” by rewarding them with sugar for correctly flying to the white card with either more or fewer black shapes, depending on which group they belonged to. Once they trained the bees, they tested how well the bees could apply the concepts they’d been trained on.
After training, about 75 percent of bees in the “greater than” group could correctly identify a card with five shapes as greater than a card with two or three shapes, and the “less than” group did the task with about 68 percent accuracy. Not honor students by any means, but not too shabby. But then the researchers threw zero into the mix as a card with no shapes, an “empty set.” When they did this, they found that the bees trained to “less than” were almost as good at discriminating an empty set from a greater number as they were at identifying two from five.
This concept, that zero is smaller than another number, sounds dumbfoundingly simple, but it’s actually a pretty abstract concept. Even as human developed numbers and math thousands of years ago, the concept of zero was not a given. It wasn’t until around 5,000 years ago that the Sumerians started using a symbol to indicate nothingness in math. Mesopotamians started using zero around 3 BCE, whereas Mayans came up with it on their own around 4 CE. India was about 400 years later, and western Europe didn’t use zero until the 12th century.
This is all to say that zero is a much more complicated thing than it appears. And with that being said, there were some situations in the experiment in which it wasn’t clear whether the bees fully grasped the concepts behind what they were being asked to do. For instance, bees in the “less than” training group sometimes chose a card with two shapes over the empty set because they were used to being rewarded for choosing two. The researchers note that this is a problem inherent in training animals to do a task: They become used to the training situation, so instead of applying the concept at-hand, they just stick to the very literal thing they were trained to do. As such, more research will be needed to tell exactly how thoroughly bees understand that nothing is smaller than something.
That being said, this research opens up new questions about whether different animals understand the concept of zero in the same way. For instance, the authors note that primate and crow brains process numbers in different regions, suggesting that their math skills arose independently, not from a common ancestor.
“An open question remains as to whether such advanced numerical understandings may be wide-spread across many animals that deal with complexity in their environments or if our findings are the result of independent evolution in honey bees,” write the study’s authors.
Abstract: Some vertebrates demonstrate complex numerosity concepts — including addition, sequential ordering of numbers, or even the concept of zero — but whether an insect can develop an understanding for such concepts remains unknown. We trained individual honey bees to the numerical concepts of “greater than” or “less than” using stimuli containing one to six elemental features. Bees could subsequently extrapolate the concept of less than to order zero numerosity at the lower end of the numerical continuum. Bees demonstrated an understanding that parallels animals such as the African grey parrot, nonhuman primates, and even preschool children.