Bumblebees have tiny brains but they can solve problems like chimps and elephants

Bumblebees figured out how to get to an out-of-reach reward in a new study, proving they can problem-solve on the fly. Mikko Törmänen/University of Oulu hide caption

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Over a century ago, the German psychologist Wolfgang Köhler conducted what became a classic experiment. He suspended a banana to keep it just out of reach of a chimpanzee, placing a pile of boxes and crates nearby. The chimp soon stacked up the boxes, climbed them and grabbed the treat.

This was evidence, Köhler believed, of spontaneous problem solving by the chimpanzee; no training was required. It was the kind of thing that humans do all the time.

Since Köhler's early work, researchers have conducted similar experiments involving an out-of-reach reward and an object to stand upon in birds and elephants . And both have solved the problem successfully.

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Olli Loukola , a behavioral ecologist at the University of Turku in Finland wondered whether bumblebees — short-lived creatures with miniscule brains — might be capable of the same task. And in a paper recently published in the journal Science , he and his colleagues present evidence that they are.

Untrained bumblebees consistently managed to roll a small Styrofoam ball into a position that allowed them to climb atop it to reach a rewarding stimulus overhead.

"I wasn't expecting that high success rate," Loukola says. He concludes that "very tiny brains can solve super complex problems."

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Expecting greatness in the smallest of packages

After studying bumblebees for about a decade, Loukola has come to expect the unexpected. If you don't have limitations on what's possible for them, he says, "you can go wild and crazy and find completely novel stuff."

His early work proved him right. He showed that bumblebees appeared able to " learn to use tools ," he says. "They learn socially from each other; they even understand the role of their partner in cooperative tasks."

Loukola has been drawn to studying tasks long considered the domain of animals with backbones. So he decided to see whether his bumblebees might be capable of a variation on Köhler's classic experiment of the banana and the box.

But he had to replicate the experiment for an organism that could easily fly to reach its reward.

Loukola, who was at the University of Oulu in Finland at the time, first trained the bees to associate a small blue circle with a sweet treat. "Bees are super fast in associating things together," he says. "They will learn immediately that blue means reward. Then they start searching for blue stuff."

He then placed just the blue circle without any sugar water on the ceiling of a hollow puck-shaped container that was about an inch high.

"We designed the arena so that it's just annoyingly [a] little bit too high for them to stand and reach the ceiling," he says, "but too tiny for them to fly."

Loukola video recorded his experiments. "With the videos, you can clearly see what is going on," he says.

In a recording of the first experiment, a bumblebee is inside the puck alongside a small Styrofoam ball. Remarkably, bee after bee in the video grabs on to the little ball and starts moving it around.

"Bumblebees, they love rolling balls," says Loukola. "Some of them needed more time and made more errors. But then they continued."

Eventually, almost three-quarters of the bees moved the ball beneath the blue dot. They then climbed atop the ball, using it like a stepstool to touch the ceiling and reach the otherwise unreachable reward.

"I planned the experiment so that it's challenging for the bees," he says. "They really need to understand the task in order to solve it."

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Cognitive flexibility

There's an alternative explanation to what motivated success in that first experiment, however. Maybe the bee wasn't purposely directing the ball towards the reward.

"It's possible that the bees don't need to understand anything," Loukola allows. "Is this really goal-directed behavior or is this just playing with the balls and solving these tasks by chance?"

So in a subsequent experiment, Loukola and his colleagues introduced barriers within the arena to block the blue dot from view. The bee could no longer see the dot unless it maneuvered around the barrier. The ball was then introduced in a different part of the enclosure.

This time, some 80% of a new batch of bees rolled the ball under the blue circle, convincing Loukola that the bees had solved the problem spontaneously. It's a first, he says, for an insect with a brain the size of a sesame seed.

"We had this underlying assumption that somehow bigger brains means more powerful computations," says Cat Hobaiter , a primatologist at the University of St. Andrews who wasn't involved in the research. "And so demonstrating this in the bumblebees is really wonderful."

Hobaiter says that this study does a good job replicating similar experiments conducted on animals across the animal kingdom. "Intelligent brains come in really diverse shapes and sizes," she concludes.

The cognitive flexibility that Loukola's individual bees demonstrated may pay off in the wild when environmental conditions change suddenly and the insects must collect pollen and nectar no matter what.

"Today they might find flowers from here, but tomorrow those flowers are not blooming anymore," says Loukola. "If the workers can flexibly find new ways to get food for the colony, that's the skill that they need to have."

And, Loukola says he has all sorts of future research ideas with bumblebees. He wants to examine their body movements, microgestures and grooming behaviors to see if the insects have a tell preceding their moment of insight. One day, it may even be possible to image the bumblebee brain while it's solving a problem like the one it was presented with here.

Loukola knows that more surprises await. The bumblebee continues to impress him.

"When I started, the [cognitive] limit was somewhere here," he says, indicating a low point with his hand. "And now it's much higher."

"We have to be smarter to develop or design experimental setups where we can test their real limits," he adds.

He's not sure what those limits are, but he knows that he hasn't reached them yet.