How Tiny Brains Accomplish Amazing Stuff
Posted by Richard Conniff on July 1, 2014
Here’s a conundrum: Insects have microscopically tiny brains and yet manage some astonishingly intelligent behaviors. Human brains, on the other hand, are massive enough to make our heads fall forward onto our desks, and yet we seem to use them mainly to find new ways to be stupid. (I am going on personal experience here.)
Honeybees, for instance, have only a million neurons in their brains, versus an estimated 85 billion neurons in a human brain. And yet the bees in a colony have to forage over an area of several square kilometers, according to the authors of a 2009 study in Current Biology, memorizing the location of flowers, sorting out which ones are more rewarding at particular times of day, then linking them in a flight pattern that’s stable and repeatable. It requires “learning landmark sequences and linking vector instructions to landmarks,” as well as “cognitive abilities previously attributed exclusively to ‘higher’ vertebrates, including, for example, simple forms of rule learning and categorization.” Meanwhile, on a typical morning the average human is still struggling to lift that massive brain off the pillow.
A honeybee must manage its daily foraging even when it isn’t driven by hunger, because its job is to gather nectar not just for itself but for the entire colony. When it comes back to the hive, fully burdened, it may need to do a waggle dance to communicate the location of a new food source to its mates. Having done all this, it may also need to tend to the housework—building, maintaining, and defending a large, complex hive.
So how do they manage it? For a new study in the Journal of Experimental Biology, Vivek Nityananda and his coauthors set up a chamber with six tiny perches, three of them containing the sugar reward honeybees crave and three containing quinine, which makes honeybees gag. To find the reward, a bee had to choose among the signals posted behind each perch. That could mean recognizing that a simple diagonal line indicated sugar, or it might entail distinguishing between two similar colors or shapes—one for sugar, the other for quinine. Just to keep things interesting, the researchers flashed these signals briefly on an LCD computer screen for 100 milliseconds, 50 milliseconds, or 25 milliseconds.
With the simple diagonal, the bees did just fine at finding the sugar, even when they had only 25 milliseconds to make their choice. But with the more complicated signals, they were befuddled at high speed. Humans and monkeys, by contrast, are capable of “ultra-fast categorization” of complex scenes, even with a glance lasting just six milliseconds. In other words, we win. (Just don’t ask us to find the honey.)
The difference suggests something about how our brains and theirs work.
We can take a single snapshot of a scene, then analyze it “off-line,” using the parallel processing powers of our larger brains. Insects don’t have that capacity, so they need to do their analysis by continuous “on-line” sampling of the scene. When approaching a target, a bee has to engage in “systematic side to side scanning movements” of its entire body, a behavior known as “peering.” Bees that are immobilized become visually impaired.
“Bees can see images quickly, and store them in memory,” writes Jamie Theobald, a biologist at Florida International University, “but may be required to physically move their eyes around in order to explore the subtle spatial content. This is a limitation, but may better accommodate an insect brain.” Sampling one slice of an image at a time may be “an important strategy that allows bees to solve complex visual problems” through serial processing, even though they lack the brain capacity to analyze a whole stored image through parallel processing.
The new study doesn’t tell the whole story. We still don’t know how honeybees map out those complex foraging routes. But what we know is impressive enough, and it reminds us that being really smart—“I’m a member of Mensa International,” “I scored genius level on the IQ test,” “I had a perfect score on the SAT”—isn’t something to brag about.
What matters is how you use what you’ve got.