The humble honeybee appears able to perceive abstract notions such as nothingness.Credit: Anand Varma/Getty

Honeybees understand the concept of zero, just like dolphins and people do. The insects can not only discern that ‘nothing’ is different from ‘something’; they’re also able to place zero at the low end of a positive numerical sequence, according to a study1 published on 7 June in Science.

Previous research has shown that honeybees (Apis mellifera) can count up to four objects2, but the new study is the first to suggest that the insects can deal with abstract concepts, says Lars Chittka, a behavioural biologist at the Queen Mary University of London. “I’ve repeatedly said I’m not surprised by any intelligent behaviour displayed by bees, but this one surprised even me,” says Chittka, who last year showed3 that bumblebees (Bombus terrestris) can learn to tug a ball into a goal by watching their fellow bees do it.

To work out whether honeybees are able to grasp the concept of nothingness, researchers lured free-flying bees to a screen with white cards, each displaying two to five dark shapes. Some bees received a drop of sweet water whenever they flew to the card showing fewer items, and others were rewarded whenever they chose the card showing more items. After a day of training, the researchers introduced cards with one or no object. Bees were consistently able to recognize blank cards as those with the lowest number of shapes. They got even better at the task when blank cards were presented alongside cards with four or five items.

“They understand there's some sort of numerical distance,” says lead study author Scarlett Howard, a biologist at RMIT University in Melbourne, Australia. “That's one very important stage of understanding zero.

It’s still unclear whether numerical competence is innate to bees or if the insects learn it through training, Howard says. Either way, she adds, the ability to understand and apply numerical rules might give bees an advantage in the wild, for example by allowing the insects to navigate or recognize different flower features.

The researchers now plan to peer into the brains of trained and naive bees to work out how neurons process the concept of ‘nothing’.