In popular culture crows are often portrayed as particularly intelligent animals. Over two millennia ago Aesop’s Fables depicted a crow that used pebbles to get a drink of water, while more recently stories have spread of birds that for generations remember the identities of people that have befriended them-or wronged them. This has led many people to ask: just how smart are these birds? They seem so different from us, is it possible that they think and view the world in a similar way? Researchers have begun to explore the striking cognitive abilities of crows and their relatives, with a recent study demonstrating that crows may possess a form of consciousness.

Episodic memory, tool use and more

Crows belong to a group of birds called the corvids, which also includes ravens, magpies and jays. Understanding cognition in corvids and other animals can be challenging, as we cannot simply ask them what they know or how they know it. Instead, researchers have used carefully designed behavioral tasks to reveal that corvids possess remarkable intellectual capabilities that may even rival those seen in primates. A classic study by Clayton and Dickinson (1998) investigated whether Western scrub jays could form episodic-like memories, meaning that they could remember the “what”, “where” and “when” of specific events. By allowing the birds to hide perishable and non-perishable foods in different locations and then return to find them sometime later, the researchers found that the birds could not only remember where they had hidden specific pieces of food, but also when they had hidden them and use this information to decide which foods to later retrieve.

Since then, more facets of corvid intelligence have been demonstrated. New Caledonian crows have shown a striking aptitude for problem solving and using tools, including a skill known as “metatool use” in which they use one tool to obtain another (Taylor et al, 2007). Their performance on this type of task was in fact comparable to that of great apes and surpassed that of several monkey species. Corvids also appear to possess a number of other abilities thought to be vital to complex cognition, including the capacity to simulate and consider the viewpoint of other individuals and the ability to learn about and apply abstract concepts to novel situations (Emery and Clayton, 2004).    

Sensory consciousness in crows

A recent study by Nieder and colleagues (2020) generated a considerable stir when it reported something even more incredible: evidence of sensory consciousness in crows. But what exactly does this mean? Are these birds “self-aware” or “capable of conscious thought” as headlines claimed? Well, not quite. Consciousness is a difficult concept to define, and its exact nature is still intensely debated. However, it has been argued that consciousness can be divided into two main types (Edelman and Seth, 2009). The first is primary or sensory consciousness, defined as the ability to integrate sensory information into a subjective experience. This subjective experience is essentially a reflection of how you as an individual experience an event. For example, you and I may go see the latest Star Wars film together, but our experiences as we leave the theater may be very different. Sensory consciousness is thought to lay the groundwork for abilities that we humans pride ourselves on, such as behavioral flexibility and reasoning. In contrast, secondary or higher-order consciousness comprises what we typically associate with self-consciousness, including self-awareness and self-reflection.

While tests of higher-order consciousness in animals remain elusive, Nieder and colleagues demonstrated that corvids may indeed possess sensory consciousness. Two carrion crows were trained on a task where for half of the training trials a visual stimulus was presented on a touchscreen, while for the other half of trials the stimulus was absent. Following a short delay, they received a cue telling them how to respond: a red cue told them to peck the screen if the visual stimulus had been presented, while a blue cue told them to peck the screen if the visual stimulus had been absent.

Of particular interest were trials in which the visual stimulus was presented but very faint, such that sometimes the birds correctly reported the stimulus as being present while other times they erroneously reported it as being absent. As a result, the animal’s subjective experience of these trials could vary even as the sensory information provided remain the same. As the birds performed this task researchers recorded from neurons within the nidopallium caudolaterale, a brain region linked to high-level cognition in birds. They found that during the delay between the stimulus presentation and response cue, cell activity tracked the animal’s perceived experience rather than the sensory information that had been presented. In other words, the patterns of cell activity during trials when the stimulus was actually absent resembled those of trials when the bird incorrectly perceived the faint stimulus as absent. Cell activity patterns were also similar between trials when the bird correctly reported the stimulus as present and “false positive” trials when the bird reported that the stimulus was there when it in fact was not. These findings suggest that crows have internal subjective experiences of events that are not just reflections of the environmental stimuli they receive.    

Are crows the “smartest” birds?

Does this mean that crows and other corvids are the most intelligent animals on Earth, behind humans and certain primates? Not exactly. There is increasing acknowledgement among scientists that attempting to compare “intelligence” across different species is an essentially futile endeavor (Colombo and Scarf, 2020). Intelligence takes many forms, and different animal species have developed unique behavioral and cognitive toolkits to adapt to the environmental challenges and evolutionary pressures that they face. So instead of asking which animals are as smart as us, it may be more worthwhile to consider what we can learn from animal species that are very different from ourselves.

 

References

Clayton, N. S., & Dickinson, A. (1998). Episodic-like memory during cache recovery by scrub jays. Nature, 395(6699), 272-274.

Colombo, M., & Scarf, D. (2020). Are There Differences in” Intelligence” Between Nonhuman Species? The Role of Contextual Variables. Frontiers in Psychology, 11, 2072-2072.

Edelman, D. B., & Seth, A. K. (2009). Animal consciousness: a synthetic approach. Trends in neurosciences, 32(9), 476-484.

Emery, N. J., & Clayton, N. S. (2004). The mentality of crows: convergent evolution of intelligence in corvids and apes. science, 306(5703), 1903-1907.

Nieder, A., Wagener, L., & Rinnert, P. (2020). A neural correlate of sensory consciousness in a corvid bird. Science, 369(6511), 1626-1629.

Taylor, A. H., Hunt, G. R., Holzhaider, J. C., & Gray, R. D. (2007). Spontaneous metatool use by New Caledonian crows. Current Biology, 17(17), 1504-1507.