How bumblebees can help us understand the evolution of human memories
Researching the way other animals’ minds work can deepen our understanding of the human mind, especially when there are differences. For example, our new study has shown that bumblebees can forget basic information within minutes, though they can still make complicated decisions. But to understand how bees’ memories differ from ours, let’s first talk about ice cream.
The other week, I visited a new ice cream shop and the sight of two flavours made my belly rumble: pistachio and chocolate brownie. I’ve had both, but never side by side. It was a tough decision. To make this choice I had to access separate memories of the two flavours. Did I recall how rich the brownies had been? Or did I remember just that I liked pistachio more than the lemon flavour I had on that spring day earlier this year?
Whether it be two ice creams or two flowers, humans and bumblebees face similar decisions. Many people think of animals as creatures which run only on instinct. But my ice cream dilemma is an example of the decisions animals of all kinds make. My PhD project explores how bumblebees make decisions and if their tiny brains come up with similar solutions to problems as we do.
Inner workings of the mind
Humans use a combination of memories to solve problems. Some memories for absolute information (say, how sweet an ice cream is), and others for comparative knowledge (such as whether it was better or worse than another option).
We aren’t the only animals who do this. A study showed that starlings remember and use both absolute (how long it took to obtain a worm) and comparative insights (whether the waiting time was shorter or longer) when deciding between new combinations of food options. But our study showed this isn’t the case for bumblebees.
I’m fascinated by how bumblebees can solve complex tasks, like cross-modal recognition (learning an object using only touch or vision and then discriminating between objects using other sensory information) and negative patterning (learning that two stimuli are rewarding but a combination of the two is not).
My colleagues and I designed a series of experiments to see what bees remembered about flowers. We trained bumblebees (Bombus terrestris) to forage from “flowers” in the lab. By flowers, I mean little coloured plastic chips propped up on vials, on which we placed little droplets of sugar water.
In the first training session, bumblebees foraged on two different coloured flowers which offered nectar of two different sugar concentrations. They quickly learned the green flower was sweeter than the yellow flower.
They then went through a second training phase with two new flowers, orange and blue. It didn’t take long for them to realise orange flowers were sweeter than blue flowers.
Finally, each bumblebee explored two flowers they hadn’t experienced together, yellow and orange, and both without nectar. This time they had to rely on two separate memories. We watched which flower type the bees landed on the most to see which they thought was better.
After just a few minutes, the bees we studied lost all memory of absolute information. They couldn’t remember anything about how sweet any of the flowers were. All they could remember is whether a flower had been better or worse.
Good things in small packages
Bees have minuscule brains with less than one million neurons, (similar in size and weight to a sesame seed) compared to our 1.3-kilogram brain with around 85 billion neurons. However, research shows tiny brained invertebrates and large brained animals aren’t that different in their brain structure. It might sound like bees have poor memories. But the way their brains evolved to store information is simply different to ours.
Diet offers one explanation. Just like humans, starlings eat a varied diet with many types of foods including fruits, worms and seeds. But adult bumblebees, like all bees, live on sugar water (and a bit of pollen) from flowers.
Perhaps the early ancestors of humans and birds, long after breaking away from the evolutionary branch bumblebees followed around 500 million years ago, needed to retain memories for absolute information to compare the varied foods they ate. But to succeed in their nectar world, bumblebees don’t need to remember anything more than which flower was sweeter.
In the wild, bumblebees tend to forage only a short distance from their nest and search for the sweetest flowers around. We know bees quickly learn where to find food, which flowers are rewarding, and how to extract nectar and pollen from them. They remember these things for the rest of their lives.
Bumblebees tend to find one good flower source and stick to it. Think about it: if you planned to only live off a diet of salted caramel ice cream you wouldn’t need comparative memories of food.
Investigating these questions in other animal species may help us learn about how important food is for memory development. For example, we could gain valuable insight if we looked at how the honey possum (a small cute mammal which drinks almost entirely nectar), and the paper wasp (a pollinating insect like bumblebees, but with a much more varied diet), remember options.
But for now, if you are ever in a predicament involving choices of ice cream flavours, my advice is: get both.
This research is funded by the National Nature Science Foundation of China (NNSFC), Templeton World Charity Foundation (TWCF) and China Scholarship Council (CSC).
source: The Conversation: How bumblebees can help us understand the evolution of human memories