Like Humans, Bumblebees May Create Mental Images in Their Brains

Say a friend or a spouse hands you a bag of groceries and asks you to grab an orange. Because you’ve seen an orange before, you’d probably still be able to dig through the bag without looking and find the citrus fruit using just your hands.

Based on information gleaned through sight alone, our brains are capable of cooking up mental versions of our surroundings with features that can be experienced by all of our senses—not just the one we used to detect an object in the first place.

This impressive, brain-bending feat is called cross-modal sensory transfer, or the ability to recognize something through one sense, like touch, after experiencing it only through another, like sight. Given its complexity, this trait was long thought to be exclusive to a few cognitive A-listers, including humans and a handful of other vertebrates like rats and dolphins.

But a new study may now be turning that assumption on its head. Even with a brain smaller than a sesame seed, the humble bumblebee appears to pass this test, too—hinting that, like us, these fuzzy, buzzy insects can generate elaborate representations of their surroundings in their minds, and stow them away for future use. The findings, published this week in Science, are a stark reminder that invertebrates and other presumably “simple” organisms are a lot more clever than we think.

“This contributes to our understanding of the inner world of an animal, to what's going on in its mind, so to speak,” study author Lars Chittka, a biologist at Queen Mary University of London, tells Sofia Quaglia at Inverse.

Plenty of previous studies have hinted at the braininess of bees. Despite having fewer than one million neurons in their brains—a paltry sum compared to humans’ 86 billion—they can add and subtract, understand the concept of zero and play soccer. Bees can recognize faces, and may even experience their own buggy versions of emotions. If any insect were a good candidate to surmount the challenge of transferring intel from one sense to another, bees would likely be it.

To test the limits of these insects’ mental acumen, Chittka and his colleagues trained bumblebees to recognize sets of spheres and cubes, some of which contained a tantalizing treat of sugar water. Some of the bugs were allowed to explore the objects through sight alone, gazing at them in well-lit conditions, but barred from making physical contact. Others experienced just the opposite, exploring their targets with touch in complete darkness. In both cases, the bees spent more time cozying up to the shapes that harbored sweets, reports Viviane Callier for Scientific American.

The researchers then performed a sensory switcheroo, exposing the dark-trained bees to illuminated conditions and vice versa. Despite only experiencing the cubes and spheres through touch, bees exposed to the light were still able to identify the most rewarding objects through sight alone. The same also held true for bees fumbling in dark, even though they’d only glimpsed the shapes from afar in previous trials.

“Bees don’t process their senses as separate channels,” study author Cwyn Solvi, a biologist at Macquarie University in Sydney, says in a statement. “They come together as some sort of unified representation.”

For us humans, skills like these come in handy when we’re grabbing a jar on a high shelf, or fumbling for our keys at the bottom of a bag. But the utility of this unusual mental ability for bees still isn’t clear, Gerhard von der Emde, a biologist at the University of Bonn who wasn’t involved in the study, tells Inverse. What’s more, mental volleying between sight and touch might not translate to communication between other senses, like smell or taste, Ludwig Huber, a zoologist at the University of Veterinary Medicine in Vienna who wasn’t involved in the study, points out in an interview with Scientific American.

Still, making use of multiple senses across space and time has likely played a role in the bugs’ evolutionary success, von der Emde says.

In humans, integrating intel across the senses is thought to play a major role in consciousness. The researchers’ findings don’t prove that’s the case in insects, whose brains are wired very differently than ours. That’s no buzzkill for the bees, though. The fact that they’ve accomplished a cognitive feat that’s even comparable to ours, von der Emde says, is “remarkable.”

Katherine J. Wu | | READ MORE

Katherine J. Wu is a Boston-based science journalist and Story Collider senior producer whose work has appeared in National Geographic, Undark magazine, Popular Science and more. She holds a Ph.D. in Microbiology and Immunobiology from Harvard University, and was Smithsonian magazine's 2018 AAAS Mass Media Fellow.