Researchers trained 8 crows to use a vending machine, then removed the model they had been copying; 6 of 8 succeeded, suggesting crows can rely on memory alone

Have you ever tried to recreate a recipe from taste alone, days after a meal that stuck in your mind, with no notes or pictures to check against? A group of wild crows might be pulling off something very close to that, but with tools instead of food. In a 2018 study titled 'Mental template matching is a potential cultural transmission mechanism for New Caledonian crow tool manufacturing traditions' published in Scientific Reports, eight wild crows were trained to operate a tiny vending machine built just for them, by the final test phase, every visual cue they could have copied from was taken away. What the birds did offers a new clue about animal memory.

The vending machine that started it all

The birds in this study were wild-caught New Caledonian crows, temporarily housed in an outdoor aviary on Grande Terre, New Caledonia, for the length of the experiment, then released back to where they were caught. For these birds, the researchers built a little wooden box with an aperture in the top. Deposit something into the machine, and a reward is dispensed, much like a vending machine. The crows were first taught how to deposit square sheets of paper into the device. Next came the challenge: the machine would only give a reward for a particular-sized sheet of card, either small or large.


As soon as each crow figured out the right size, there was another change to the test. This time, instead of being supplied with pre-cut pieces, the crows were provided with uncut large sheets of paper and had to tear a piece for themselves and put it in the machine, without any size model present anywhere around. The catch was that during this phase, the machine rewarded them randomly. It didn't matter what size piece they tore. There was no model to imitate and no reward tied to size, which is what makes it notable that some crows still worked to match a size they could no longer see or be rewarded for: it suggests the behavior was driven by memory rather than by the immediate incentive.

What the crows actually built

Of the eight crows, six tore pieces that matched the size they had learned previously, not the newer size. The study notes that the ability of the birds to do so improved with practice, and they could rip the pieces more and more towards the correct size with each trial. The two crows that did not follow the above pattern were relatively young, less than two years old. One adult female, Emma, stood out. In several instances, the researchers noted that she tore a piece of paper and continued tearing it until it better resembled the memory of the correct size, and then dropped it in. Overall, out of 40 pieces she created during the experiment, 39 were closer to the correct template. This is unlikely to be explained by mere guessing; it suggests a bird working from a mental picture, adjusting until the piece matched.

Why "copying" isn't the right word here

This matters since New Caledonian crows have a reputation problem in science. These crows are known for making complex tools, including hooked twigs and pandanus-leaf barbs, as documented in earlier research on the species' tool-making behavior. However, past studies have shown that these animals do not copy one another's actions directly. In a separate study titled 'How New Caledonian crows solve novel foraging problems and what it means for cumulative culture' published in the journal Learning & Behavior, this theory was tested through the use of a foraging task. It showed that crows who observed a trained crow spent more time exploring the particular area of the foraging task but did not imitate their solution technique.

So, if crows aren't copying actions, how do wild populations end up making the same tool shapes for generations? The vending machine study offers one possible answer. Rather than imitating a particular action, a crow could form a mental image of the desired tool and rebuild it using its own technique. Scientists liken this to the process of songbirds singing songs. A baby bird does not imitate the way its parents move their throats. It listens, recalls the melody, and then later figures out how to make the sound itself.

How this plays out for real, in the wild

None of this happened in a laboratory vacuum. This is consistent with what is known about the development of young crows in the wild. The studies conducted on wild crow families titled ‘Social learning in New Caledonian crows’ have found that the offspring remain with the parents throughout the whole year, using the tools made by the adults to feed until the offspring learn to produce them. This gives young crows time to form a concept of the right tool long before they begin building one themselves.

Why this should matter to you

We often believe that tool-making skills require either teaching or copying to survive across generations. However, this study suggests that a mental image stored in memory and checked later may be enough to pass on the tradition. It means that a mental image alone, held in memory, and compared with what comes later, can be enough to keep a tradition alive. It’s the sort of discovery that makes you wonder how much of what we think is uniquely human; remembering a goal and working backward to reconstruct it, might already be tucked away inside a bird’s brain. As the researchers note, this was just one experiment using an artificial task with only eight crows. It suggests crows have the cognitive ability to do this task. However, how tool designs spread across wild crow populations over generations is still being studied. But for a species already known for beating puzzle boxes, it's one more reason to stop underestimating what's going on in that black-feathered head.