But then they got another test: The researchers presented the bees with a card that had a single symbol — and a blank card that had nothing on it.
The bees seemed to understand that “zero” was less than one, because they flew toward the blank card more often than you’d expect if they were choosing at random — although they weren’t that good at distinguishing between the two.
It got easier for them when they had to compare zero with a larger number. “When we showed them zero versus six, they did that at a much higher level than zero versus one,” Howard says. “So what tells us is that they consider zero as an actual quantity along the number line. They’re actually better at doing zero versus six because those two numbers are further apart.”
“We were very surprised and happy, excited, to see that actually the bees were choosing the empty paper,” says Aurore Avargues-Weber, a CNRS researcher with the University of Toulouse.
Even very young children, she points out, have trouble understanding that zero is a number. “It’s easy for them to count ‘one, two, three, four,’ but zero, it’s nothing, it’s not something to count. So it’s not the same category,” she explains.
She had expected that the bees would see a blank paper as something irrelevant that was completely different than what they had been trained on, because to understand zero, “brains need to represent something out of nothing. It’s not trivial.”
What’s more, the brains of bees are incredibly tiny brains compared with the brains of humans, Nieder notes. “Bees really have a mini-brain with fewer than one million brain cells,” he says, “compared to 86 billion nerve cells in our brain.”
Even so, the bees can understand the abstract concept of an empty set — the precursor or prerequisite to understanding the symbolic number zero — and he says he found that very surprising.