To make collective decisions, ants behave like individual neurons in a larger brain

Solitary ants might be insignificant in the big scheme of things, but together they can do incredible things. That’s the crux of the movie Antz (now streaming on Peacock!), not to mention a whole host of other stories reinforcing the idea that we’re stronger together than we are alone. It also turns out to be true of ants in the real world.

An ant alone isn’t particularly smart. They mostly function by way of chemical stimuli, using smells to detect food and navigate their way to and from the colony. Ants together, however, exhibit emergent behaviors greater than the sum of their parts. In a new paper published in the Proceedings of the National Academy of Sciences, researchers from the Laboratory of Social Evolution and Behavior at The Rockefeller University found that colonies of ants behave similarly to networks of neurons, allowing them to make collective decisions they couldn’t make alone.

An individual ant’s brain only has about a quarter of a million neurons, as compared to roughly 86 billion in humans. But an average colony can have hundreds of thousands of individuals. That’s a lot of computing power if you can get it to work together, and it turns out that ants can.

To test the ways in which ant colonies make decisions, scientists set up an arena in which colonies of varying sizes were exposed to rising temperatures. The question they set out to answer was when the colony would decide to leave the area and why. Making the decision to leave involves balancing two opposing forces, the threat of rising temperatures and the cost of leaving home. In order for a colony to abandon their nest, the threat of staying has to outweigh the cost of pulling up stakes.

If the ants were leaving home individually or as a sort of scattered evacuation, that could be explained away as individuals making choices for their own safety and well-being, but that’s not what researchers saw. Instead, individuals tended to stay put even as temperatures increased, until a threshold was met. Then they all moved out together in a coordinated fashion. It appears, for all intents and purposes, as if they’re operating as a single unit.

Experimental observations revealed that when it comes to ants evacuating their homes, there are two conditions at play: the severity of the temperature increase and the size of the colony. Changes in behavior as a function of temperature make a sort of intuitive sense. The higher the temperature the more quickly you might abandon ship. However, the difference in response as a function of colony size was something of a surprise. Researchers found that the larger the experimental colony was, the longer they waited to pack up and move. That’s especially interesting because an individual ant is likely unaware of the overall size of their colony.

Researchers believe this might be a consequence of the way ants communicate with one another. In larger colonies, it might simply take longer for information to spread and reach the required threshold for action. There could also be a more practical element at play, a simple matter of logistics. Moving a few dozen ants isn’t all that difficult while moving thousands is more cumbersome. Smaller colonies might simply have more fluidity in their movements and are thus able to be choosier about the conditions they’ll accept.

In future studies, researchers hope to better define the mechanisms through which ant colonies transmit information between themselves and emerge at computational abilities beyond the ability of the individuals. In the meantime, it seems clear that they benefit from open lines of communication and listening to their peers. Maybe we could learn something from that.