One of the most enjoyable facets of studying other species is discovering the amazing things they’re capable of. As humans, the things we tend to find most amazing are the abilities that remind us the most of, well, us—parrots that can speak, bonobos that play Pac-Man, monkeys that use rocks like hammers to crack nuts, and so on. That can create a bit of a bias when we evaluate human intelligence in comparison to other species. As Robert Brault put it, “If a rabbit defined intelligence the way man does, then the most intelligent animal would be a rabbit, followed by the animal most willing to obey the commands of a rabbit.”
The better we get at examining intelligence in other species on their own terms, the richer the picture of their cognition becomes. In many cases, the idea that some human trait or ability is utterly unique among the animals is cut down in the process. Chimpanzees and bonobos, our closest relatives, are most similar to us and do the majority of the humbling. There are, however, much more distantly related species that have joined in the game. One such group is the crows (and the corvid family in general), which can use tools—including traffic patterns—and solve complex problems.
Studies have demonstrated that crows can learn to recognize human faces, and hold onto that memory (and sometimes a grudge) for a long time. Researchers from the University of Washington wanted to go deeper and understand how they do so at the level of the brain. They were interested to find out whether crows recognized faces using the same neural processes as humans, or in another way with which we were not yet familiar.
To find out, the researchers captured twelve wild American crows while wearing a particular mask of a human face. For four weeks following their capture, they fed and cared for the crows while wearing a different mask. The idea was to see if the birds would recognize one face (mask) as the “threatening” one that captured them, and the other face as the “caring” one that brought them delicious food.
One by one, they took the crows and presented them with a view of one of the two faces, or simply an empty room. Since you can’t keep a crow calmly strapped inside a brain scanner while this is going on, they gave the crows a chemical that functions as a sort of dye or marker. When a part of the brain becomes active, it takes in this chemical from the bloodstream. Afterward, they anesthetized the crow and placed it in a PET scanner. The areas of the brain that contained the chemical marker showed up clearly, allowing the researchers to see what parts of the brain had been busy while the crow was checking out the sights they were shown.
From the images (as well as the crows’ behavior), they were able to tell that the crows recognized the “threatening” and “caring” faces as just that—no surprise there. Interestingly, they did so by using the same regions of the brain that humans do when they process images of faces and associate them with the relevant emotions.
Why is this useful information? The researchers explain, “Understanding how wild animals integrate perception, memory, and emotion to behave adaptively may allow researchers to generalize important findings across species and sensory modalities, develop strategies to lower stress in captive animals, shape animal actions to reduce human-wildlife conflicts, and engage the public to appreciate the cognitive capacity of other species.”
The name’s Detective Crow
Facial recognition not good enough for you? Another recent study takes on a much more complex cognitive task—reasoning that some agent is responsible for an observed action, even when that agent is nowhere to be seen. (No, the crows are not developing government conspiracy theories surrounding their capture and interrogation…)
The researchers give an example: Say you’re a bird sitting high in a tree. If you see a monkey swinging through the branches of a neighboring tree, shaking the leaves in the process, there’s no mystery here. But what if you only see the shaking leaves, with nary a glimpse of a responsible monkey? It may seem like a simple step to recognize that the movement must be caused by a hidden monkey, but think about how complex that thought really is. You have to recognize the pattern of leaf movement as different from the usual rustling in the wind, call up possible explanations abstracted from your memories, and select the one that fits best.
Researchers have tried to elicit this type of thinking from nonhuman primates, but haven’t had much success. “However,” the authors of this recent study argue, “no studies have attempted to recreate ecological situations… where the ability to make inferences about hidden causal agents would be highly adaptive.” In other words, we’ve been asking them to demonstrate these abilities in very artificial situations, rather than in their element.
In this experiment, the researchers used eight New Caledonian crows—famous for their use of sticks as tools to procure meals. The crows were placed in a room with a box from which they could retrieve food by using a stick. Near the box was a blind behind which researchers could hide. A hole in the blind near the food box allowed the researchers to poke a stick through that would hit any crow trying to use the box in the back of the head. (Don’t worry—the researchers expressly avoided doing so.)
First, two researchers entered the room—one went behind the blind and one stayed in plain sight. The one behind the blind would push the stick through the hole a number of times, and then both the humans would leave the room. In the second version, one researcher would enter the room and stand in plain sight while the stick was manipulated from outside the room (via pulleys) and then leave the room. In each case, the behavior of the crow was monitored after the humans left. They watched to see how many times the crow eyeballed the hole to make sure a stick wasn’t coming out while it used the food box. (Watch the video below to see this in action.)
The idea was this: if the crows were capable of thinking of the stick as being manipulated by a hidden human, they wouldn’t worry about the stick once the human behind the blind left. When the stick did its thing, but no human walked out, on the other hand, they’d be very suspicious that the stick would start moving again at any moment.
That’s exactly what happened. When no human emerged from behind the blind, the crows were clearly nervous. They inspected the hole much more frequently, and retreated from the box without successfully getting the food on several occasions (which never occurred in the first scenario).
This indicates that though the crows could not see the person behind the blind, they knew that person was moving the stick. They didn’t trust the food box to be safe until they saw somebody leave the blind.
“It is, therefore, possible,” the researchers write, “that the ability to reason about hidden causal agents is far more widespread in the animal kingdom than has been thought previously.”