Chimps and bees can also perform “uniquely human” behaviour
Comparative psychologists are abuzz with excitement as bees and chimpanzees show evidence of a capability previously thought to be exclusive to humans.
27 March 2024
By Emma Young
Every day, we benefit from accomplishments and inventions that are far too complicated for any single person to have developed from scratch. Evidence of this so-called 'cumulative cultural evolution' is everywhere — from the cars on our roads to the TVs in our homes.
Our ability to learn from other people is key to this, and it's been argued that such 'social learning' is unique to humans. However, two recent studies provide strong evidence that other species can, in fact, learn complex, helpful behaviours from others that they wouldn't have developed on their own. The first study was on chimps, and the second was on a much more distantly related, but also highly social, species: bumblebees.
Edwin Van Leeuwen at Utrecht University led the research on chimps, published in Nature Human Behaviour. In it, team created what was essentially a peanut vending machine. In order to get the peanuts, a user had to follow a series of steps: pick up a ball, pull open a sprung drawer in the side of the plastic box to reveal a hole, and place the ball inside said hole. Then, they had to allow the drawer to spring shut. This triggered the release of peanuts into a compartment beneath the drawer.
The team put a vending machine device, as well as plenty of suitable balls, into the forested enclosures of two groups of a total of 66 semi-wild chimpanzees, all housed in a centre in Zambia. After three months, despite hundreds of attempts by the animals to get at the peanuts (including two instances of the lid being wrenched off), not a single one had managed to crack the steps needed to get the reward. This suggests that they were unable to acquire the knack without being shown.
The researchers then took one mid-to-high-ranking adult female from each group, trained them in how to use the machine (a process that required eight twenty-minute training sessions), and put them back into their groups. The trained animals were quick to put their newly acquired skill into use — and this was not lost on their fellow chimps.
By watching the trained 'instructor', a total of 14 other chimps learned how to perform the correct sequence of steps to obtain peanuts. This wasn't a rapid process. Typically, an observer had watch the machine being used at least nine times before they successfully used the technique themselves. But it did happen, and the researchers also observed that the more times chimpanzees watched the task being solved, the faster they were to start interacting with the box, and the more rapidly they solved it themselves. Here, then, is evidence of social learning among chimpanzees.
Given past scepticism about social learning in non-human animals, this finding is clearly important. But, perhaps even more remarkably, Alice D. Bridges at Queen Mary University of London and colleagues recently observed something very similar for bumblebees.
In their paper, published the same day in Nature, this research team created a box containing a sugary reward. To get access to it, a bee had to push a blue tab on the box away from the path of a red tab, before pushing the red tab in. (Video of this can be seen here.)
The team left this box, with its sweet and tempting contents, with two bumblebee colonies for 12 days and another colony for 24 days. Sometimes they left the box shut, other times it was left open. During the periods that it was shut, "no bee came close to opening even a single box," the team writes, "and their interest in the closed boxes plummeted with time."
The team then trained individual bees in how to do it. This wasn't easy. To help the bees to grasp the sequence, the researchers had to temporarily offer a sweet reward for the first step of pushing the blue tab out of the way. But, after two days of training, these bees got it.
Next, trained bees were paired with 15 untrained observers, and together, they were given access to the closed puzzle boxes. The researchers found one third of the observers learned how to open the box. Three of these bees were successful on their first attempt, while the other two took three goes. As the team notes, these observer bees had never been exposed to any kind of puzzle box before, they had not learned either of the two steps before watching the trained bee perform them, and, unlike the trained instructors, they had never been rewarded for pushing the blue tab. "Yet they were able to acquire the entire behaviour sequence through social learning."
These new studies represent the first experimental (rather than anecdotal) evidence for social learning in animals. In theory, this type of learning could, as Van Leeuwen and colleagues write, "catapult" cumulative cultural evolution. This has clearly happened for humans. And yet, as the bumblebee team notes, among this species, at least, there is no evidence for any cumulative culture at all. "Why," they write, "they are capable of such a feat, if it is not something necessary in their natural lives, remains an unanswered question." It's surely one, though, that teams will now be pursuing with interest.
