Understanding the concept of zero is surprisingly difficult. The honey bee has joined the ranks of dolphins, parrots, primates and preschool children, in demonstrating the ability to distinguish zero on the numerical spectrum. This finding raises questions of how a species that differs so much from humans – with fewer than one million neurons in its brain, compared to a human’s 86,000 million neurons – can share such a complex skill, and how it benefits the tiny insect in its environment. By demonstrating that even tiny brains can comprehend complex, abstract concepts, the surprise finding opens possibilities for new, simpler approaches to developing Artificial Intelligence.
While intuitive to modern humans, the full understanding of zero is an advanced numerical concept that’s challenging to grasp; several ancient human civilizations lacked the full understanding of zero in their numeric systems. Recently, scientists have shown that some vertebrates can understand the concept, and now, Scarlett Howard and colleagues present evidence that honey bees – though remote from the mammalian branch of evolution – are also part of this “elite club.” Turns out that honey bees can rank numerical quantities and understand that zero belongs at the lower end of a sequence of numbers
Free-flying bees were lured to a wall containing white squares each with a different number (from two to five) of black shapes. The bees were trained on “greater than” and “less than” concepts with food rewards (the “less than” group was rewarded for flying toward the display with fewer items, for example).
The researchers then introduced two numbers the bees hadn’t yet seen in their training – one and zero. The bees were consistently able to distinguish zero as lower than one. Interestingly, they were more accurate when zero was presented with a more distant number choice – a trait also seen in humans.
Associate Professor Adrian Dyer, from RMIT University in Melbourne, Australia, said the number zero was the backbone of modern mathematics and technological advancements. “Zero is a difficult concept to understand and a mathematical skill that doesn’t come easily – it takes children a few years to learn,” Dyer said. “We’ve long believed only humans had the intelligence to get the concept, but recent research has shown monkeys and birds have the brains for it as well. What we haven’t known – until now – is whether insects can also understand zero.”
As well as being a critical pollinator, the honey bee is an exceptional model species for investigating insect cognition, with previous research showing they can learn intricate skills from other bees and even understand abstract concepts like sameness and difference.
PhD researcher Scarlett Howard set out to test the honey bee on its understanding, marking individual honey bees for easy identification and luring them to a specially-designed testing apparatus. The bees were trained to choose an image with the lowest number of elements in order to receive a reward of sugar solution.
For example, the bees learned to choose three elements when presented with three vs. four; or two elements when presented with two vs. three.
When Howard periodically tested the bees with an image that contained no elements versus an image that had one or more, the bees understood that the set of zero was the lower number – despite never having been exposed to an “empty set.”
Dyer, a researcher in the Bio Inspired Digital Sensing-Lab (BIDS-Lab), said the findings opened the door to new understandings of how different brains could represent zero. “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?
“How does a brain represent nothing? Could bees and other animals that collect lots of food items, have evolved special neural mechanisms to enable the perception of zero?
“If bees can learn such a seemingly advanced maths skill that we don’t even find in some ancient human cultures, perhaps this opens the door to considering the mechanism that allows animals and ourselves to understand the concept of nothing.”