Joyful Leaping Dolphins, Brooding Crows… Consciousness in Animals

How does consciousness emerge from a physical world? Why do some neural events result in conscious experience while others do not? And most importantly, what exactly is this thing we call consciousness?

The famous thinker Descartes identified consciousness with “thinking” and coined his famous phrase: “Cogito, ergo sum” (I think, therefore I am). The concept of consciousness has long been debated, capturing the attention of both philosophers and scientists. In the broadest sense, consciousness can be defined as an individual’s awareness of their existence and environment. This concept encompasses elements such as sensitivity, awareness, subjectivity, qualia (subjective experience), the ability to experience or feel, wakefulness, and a sense of self.

But what about animals? Can we speak of consciousness in non-human animals? How much do we know about the inner worlds of animals? Have you ever wondered what might be hidden in a dog’s “loyal” gaze, an elephant’s “sad” eyes, or a dolphin’s “joyful” leaps? For example, elephants can recognize themselves in mirrors, which is considered a sign of self-awareness. But how deep is this awareness? Can a dog understand its owner’s emotional state? Can a bird plan for a future event?

The question of whether animals are conscious, and the extent of their consciousness has been debated for a long time. Answering this question requires examining the complex behaviors and brain structures of animals.

The “New York Animal Consciousness Declaration,” signed this April, reviews numerous studies conducted over the past decade. It suggests that consciousness is now a “realistic” possibility not only in birds and mammals but also in reptiles, amphibians, fish, cephalopods like octopuses and cuttlefish, crustaceans like hermit crabs and crayfish, and insects like bees and fruit flies.

Signed by 288 researchers so far, the declaration states that they focus on a significant concept referred to as “phenomenal consciousness” or “sentience.” They describe it on their website as follows: “The question here is which animals can have subjective experiences. These sensory experiences (for example, the experience of a particular touch, taste, sight, or smell) and experiences that feel good or bad (for example, pleasure, pain, hope, and fear) can be included.”

This was also what American philosopher Thomas Nagel had in mind in his famous essay “What Is It Like to Be a Bat?” when he argued that every creature has its unique conscious experience that cannot be fully understood from the outside.

Consciousness is a subjective experience and more than just the ability to perceive stimuli. However, the requirement for consciousness is not the use of “language” or complex abilities like “reason” as in humans. Phenomenal consciousness is raw sensations. The use of language in humans allows for some experiences that animals do not have. For example, we can talk to ourselves about a topic that occupies our minds, make decisions, and feel happy or sad as a result of this internal conversation. An ant cannot experience this, but what if it has different forms of experiences that we do not possess?

Let’s take a look at a few of the studies that led scientists to sign this declaration, revealing the “realistic” possibility that animals also have consciousness.

Crows

Crows are among the smartest creatures in the animal kingdom. They can solve complex problems, such as puzzles that require following specific steps in the correct order to achieve a goal. They can also make and use tools, such as hunting with sticks and hooks. According to one study, they have an innate neurological brain structure for distinguishing quantities, i.e., numerical cues. In short, these unique birds are believed to possess remarkable cognitive abilities. Moreover, there are emerging clues that they might have the capability for subjective experiences, a trait previously observed only in humans and primates. A 2020 article published in the journal Science claims that crows are as cognitively skilled as primates.

Andreas Nieder and his team at the University of Tübingen conducted a study suggesting that what we call ‘consciousness’ may not be limited to humans and primates. During the experiment, various shapes were shown to crows on a screen. Some shapes were bright and clear, while others were very faint and barely noticeable. The crows were trained to peck at a red light when they saw a shape and a blue light when they did not. In some trials, they were taught to respond when the blue light was shown if they did not see a shape on the screen, while no action was required when the red light was shown. After the training, electrodes were attached to the NCL region of the crows’ brains, which is thought to be associated with high-level cognitive processes, and the experiment began.

When the crows answered ‘yes,’ intense brain activity was observed during the short period from the presentation of the visual stimulus until the point they responded. However, in cases where the answer was ‘no,’ no brain activity was observed. The researchers could predict the crows’ responses with certainty by monitoring their brain activity. Whether the shapes were bright or dark, clear or faint, the crows’ neural responses to visual stimuli were of varying characteristics. According to Nieder, neurons responded not to the stimuli shown to the crows but to what the crows perceived after being exposed to these stimuli. In other words, this is claimed to be definitive evidence that nerve cells capable of generating subjective experiences exist in the brains of crows.

Octopuses

The name ‘octopus’ is derived from the Greek word for ‘eight-footed’ and is considered one of the most peculiar animals on the planet. These invertebrate sea creatures have blue blood due to a copper-based protein called hemocyanin, three hearts that pump blood to their organs and gills, the ability to change skin color and texture for camouflage, the highest brain-to-body ratio after mammals, and are known to be quite intelligent. In fact, some experiments show that each arm has its own mini-brain governed by a central brain system. They have roughly as many nerve cells as dogs (about 500 million), two-thirds of which are located in their arms and one-third in their doughnut-shaped brain.

Octopuses can escape from mazes, perform sneaky operations like escaping from their jar to eat fish in another jar and then returning to their jar without forgetting to close the lids and use tools such as building shelters with stones, shells, and similar materials. Thanks to their excellent vision, they can recognize and remember even human faces.

In addition to all this, a study conducted in 2021 determined that octopuses can make conscious decisions to avoid pain. Cephalopod expert Robyn Cook applied a method called ‘conditioned place preference,’ originally developed for lab mice, to octopuses by creating two separate compartments in a water-filled aquarium and having the octopuses choose one. When an octopus entered a compartment, acetic acid was injected to cause physical pain, and it was noted that these octopuses subsequently avoided entering that compartment again. Then, when one of these octopuses entered the other compartment, local anesthesia (lidocaine) was injected to relieve the pain. The octopuses that were first (unfortunately) injected with acid and then had their pain relieved began to show a preference for the compartment where anesthesia was applied. It was also noted that this behavior pattern did not develop in octopuses that were injected only with seawater for control purposes of the experiment. Previous experiments on mammals revealed a pattern where the physical pain caused by acid injection was alleviated by lidocaine, and it was understood that octopuses behaved in the same pattern, thus experiencing persistent subjective pain and choosing to avoid a specific location as a result.

Cuttlefish

Cuttlefish are mysterious sea creatures; they have eight legs, blue blood, three hearts, and high intelligence like octopuses, and are renowned for their strong memory. According to studies that monitor brain activity while they sleep, it is believed that they might even dream.

Cuttlefish can remember where, when, and what they ate, and shape their future feeding decisions based on these memories. If they know they can find a delicious meal later, they can skip a less tasty one, exhibiting behavior known as ‘delayed gratification,’ which is only known from primates and is considered a sign of self-control and intelligence. In experiments, cuttlefish were presented with two different types of food: one they didn’t prefer much but was part of their diet (king prawn), and the other, a type they loved (grass shrimp). The subject could only reach its preferred prey if it refrained from eating the king prawn. The experiment concluded that cuttlefish could wait for more than two minutes, which is almost the same duration observed in experiments conducted with chimpanzees.

However, this behavior might have originated from another behavior. Cuttlefish can camouflage and remain motionless for a long time to protect themselves from predators and go for brief feeding excursions meanwhile. So they know what it means to wait. But of course, the level of self-control, patience, and intelligence varies from species to species among cuttlefish. Additionally, it is worth noting that while it was waiting for its preferred food, it turned its back on the other prey in order not to see it, possibly trying not to succumb to its temptation.

Another study conducted in 2020 to test this behavior in cuttlefish that know the taste of a good meal claims that this invertebrate sea creature can remember not only where, when, and what it ate but also how it experienced it. Researchers exposed cuttlefish to the sight or smell of a crab, fish, or shrimp and trained them to indicate whether they remembered these creatures by their appearance or smell three hours later. After training, repeated tests with an unfamiliar creature (a mussel) showed that cuttlefish could recall details of an experienced event (whether they smelled or saw it).

Moreover, the memory of cuttlefish does not deteriorate as they age. Another experiment found that cuttlefish in the final weeks of their lives had as strong a memory as younger adults. Experts suggest that this might be because cuttlefish do not have a hippocampus, the brain region associated with memory in humans and other vertebrates.

The ability to recall past memories with various details and relive them is called episodic memory, and the ability to make future decisions based on this skill could mean having a complex brain structure and signs of consciousness.

Cleaner Wrasse

The mirror test is a method used to test an animal’s self-recognition capability. It was developed in 1970 by American psychologist Gordon Gallup Jr. to determine whether animals (and infant humans) can recognize themselves in a mirror. Essentially, a mark (such as a smudge of soot) is placed on the animal being tested, and if the animal touches or tries to remove the mark when faced with its reflection, it is considered to recognize itself. So far, primates, killer whales, bottlenose dolphins, some magpies, and elephants have passed the test successfully. Those of us who have cats or dogs at home probably know that our pets fail the mirror test. Although the test gives an idea of whether an animal can recognize itself in the mirror, it does not provide a definitive answer about self-awareness because self-awareness actually encompasses an animal’s awareness of its own mental state, emotions, thoughts, and physical appearance. Self-recognition is a concept limited to recognizing physical appearance only.

Interestingly, another animal that has successfully passed this test is a fish. Researchers from Osaka City University, led by Masanori Kohda, first tried the test on a species of cichlid. Although cichlids are very intelligent and can individually recognize their family members, they failed the mirror test. Kohda then tried his luck with the cleaner wrasse (Labroides dimidiatus), a tiny tropical marine fish known for feeding on dead tissues and parasites on other sea creatures. Kohda placed ten wild cleaner wrasse in an aquarium with a mirror. Initially, most of them perceived their reflection as another fish entering their territory and trying to attack it, but soon the events took an interesting turn. Behaviors such as approaching the mirror belly-up or rushing towards it and stopping at the last moment showed researchers a spark of perception that the reflection might be their own. In the second phase of the experiment, a harmless dye was used to mark the fish’s throat. The cleaners, who had practiced in front of the mirror, tried to remove the mark by rubbing against surfaces after they saw their marked reflection. They even checked in the mirror to see if the mark had disappeared afterward. The marked subjects exhibited this behavior only after looking in the mirror (those who did not encounter the mirror continued with their lives unaware of the mark), showing researchers that the fish might have understood that the reflection in the mirror was their own. Kohda said, “I actually fell off my chair when I watched the videos.”

Some experts argue that this behavior might stem from the fish’s feeding habits; the fish, which needs to successfully detect similar marks on other fish to feed, might be exhibiting such behaviors as part of its normal habits rather than as an indication of self-awareness or self-recognition. In other words, it is possible that the fish is rubbing against surfaces to encourage the ‘other fish’ in the mirror to remove the parasite it sees on itself.

Regardless, it is a significant possibility that self-awareness and self-recognition traits might be present in more organisms than we think in the animal kingdom.

Snakes

Self-recognition in animals has been studied for many years. However, the mirror test conducted on Lapin fish was based on vision, so it could not be used in more odour-dependent creatures such as snakes.

In a groundbreaking study from Wilfrid Laurier University in Canada, three psychologists, Troy Freiburger, Noam Miller, and Morgan Skinner, found evidence that at least one species of snake might possess self-recognition abilities. Published in April 2024, the study tested snakes using their sense of smell instead of sight.

The researchers selected two easily accessible snake species: garter snakes and ball pythons, involving 36 garter snakes and 18 ball pythons in total. They collected scent samples from each snake using a cloth and then presented five scented pads to each snake. These pads included the snake’s own scent, its own scent mixed with olive oil, the scent of a different snake species, and plain olive oil. The researchers closely observed the snakes’ reactions, particularly their tongue flicking behavior.

The results were surprising! Garter snakes showed more tongue flicking in response to their own scent and the altered scent compared to other scents. Ball pythons, on the other hand, did not show significant differences in their reactions to the various scents.

The researchers believe that the increased tongue flicking in response to altered scents indicates that garter snakes can recognize themselves through their smell. This suggests that garter snakes can detect changes in their own scent. The researchers also noted that garter snakes are more social than ball pythons, which might explain the behavioral differences. This study offers exciting evidence of self-recognition abilities in snakes.

Zebrafish

Zebrafish are small, colorful freshwater fish popular in home aquariums and frequently used in scientific research to study behavior. A recent study explored the curiosity of zebrafish.

Researchers housed groups of zebrafish in semi-natural tanks and introduced 30 new objects to each group. They measured the time it took for the fish to approach the objects, their interest in the objects, social dynamics, and diving behavior (a stress response in zebrafish).

The results showed that zebrafish approached all objects easily and displayed neophilic behavior, meaning they were interested in new stimuli. The fish also maintained an interest in some objects at the beginning of the study, indicating their motivation to explore and examine new things.

Additionally, researchers observed that zebrafish groups displayed specific interest in new objects at the start of object presentations, showing that the fish could distinguish and show special interest in individual new objects. This study suggests that curiosity in fish, like in other animals, is linked to seeking out information and could be important for their well-being. Curious fish might be more motivated to explore their environment and learn new things, making them less stressed and more adaptable.

Bumblebees

Play is not just for humans; it is observed in many animal species and is believed to contribute to the healthy development and maintenance of cognitive and motor skills. Play can benefit vital functions like foraging strategies and is considered an important indicator of animal welfare.

It is well known that various animals interact with and manipulate inanimate objects “just for fun.” The most evident examples of object play come from mammals and birds. But can insects also play with inanimate objects? A new study provides an answer.

Scientists at Queen Mary University of London discovered that bumblebees (Bombus terrestris) in a lab environment engaged in surprising behavior: rolling wooden balls. This finding suggests that bees might have complex behaviors and even experience enjoyment, highlighting the importance of protecting bees in the wild and improving their care in hives.

Researchers quantitatively assessed the bees’ ball-rolling behavior, noting that while some bees rolled balls once or twice, others repeated the activity up to 44 times a day. This high frequency suggests the bees enjoyed the activity.

To confirm that ball rolling was a preference, a new experiment was conducted with a different bumblebee nest. Bees had to pass through a room to access food, which initially contained wooden balls for the first 20 minutes. The room’s color was then changed, and the balls were removed. The colors were alternated six times, training the bees to associate the color with the presence of balls. Finally, the bees were given a choice to enter either a yellow or blue entrance without visible balls. According to the researchers in Animal Behaviour, bees preferred yellow, likely associating it with the enjoyable ball-rolling activity. When the colors were reversed, similar results were obtained. This suggests that bees might spend time rolling balls for enjoyment rather than solely for essential functions like foraging.

Crayfish

Crayfish, freshwater crustaceans from the class of arthropods, might seem like simple creatures you notice in aquariums or under river rocks. But can these fascinating animals experience anxiety and stress like us?

To understand crayfish’s response to stress, researchers subjected one group to mild electric shocks and placed them in a specially designed water tank. This tank had two illuminated and two dark arms. Stressed crayfish avoided the illuminated arms, while non-stressed crayfish hesitantly explored them, driven by their foraging instinct.

In another part of the experiment, researchers found elevated serotonin levels in stressed crayfish, the same neurotransmitter that increases in stressed humans. Injecting crayfish with serotonin alone also triggered protective behaviors. Additionally, injecting them with chlordiazepoxide, a human anxiety medication, calmed them down. Subsequently, stressed crayfish behaved more like non-stressed ones, showing more willingness to enter the illuminated areas.

Scientists suggest that while crayfish may not feel anxiety and stress exactly like humans, the underlying mechanisms are quite similar, pointing to a common evolutionary origin. These findings help us better understand the emotional similarities between animals and humans and could lead to more effective treatments for stress and anxiety in the future.

Crabs

Crabs are arthropods belonging to the class of crustaceans. There are hundreds of crab species worldwide, inhabiting oceans, freshwater bodies, and land. Crabs are generally known for their hard shells and claws, and they exhibit various feeding habits; some are herbivorous, others carnivorous, or omnivorous.

The idea that invertebrates feel pain is often dismissed with the claim that their responses to harmful stimuli are merely reflexes. Reflexes do not require higher-level processing, whereas the experience of pain does. One way to test this claim is to investigate whether animals respond solely to harmful stimuli or if these responses are influenced by other motivations.

Robert Elwood and his colleagues from Queen’s University Belfast in Ireland conducted a study, published in the journal Animals, to understand if crabs possess pain perception and how they make decisions when faced with risk.

The team placed shore crabs (Carcinus maenas) in a lighted environment, providing a dark refuge for them to escape to. However, the twist was that some crabs received mild (6 volts) or more intense (12 volts) electric shocks when they entered the refuge. This allowed the researchers to observe the crabs’ preference between avoiding bright light and avoiding electric shocks.

When crabs received an electric shock, they began to use the dark refuge less and preferred to stay in the bright light. However, their preferences varied depending on the brightness of the light and the intensity of the electric shock. Bright light and high-voltage shocks led to crabs avoiding the refuges. Additionally, crabs that received shocks showed signs of anxiety during the decision-making process.

These findings indicate that crabs act through a more complex decision-making process rather than simple reflexes. Pain is generally considered a vital warning mechanism to avoid harmful situations. The behaviors observed in crabs provide significant clues that they may indeed feel pain.

Fruit Flies

Fruit flies (Drosophila melanogaster) are one of the most commonly used model organisms for genetic and biological research. Measuring about 3 mm in length, Drosophila are popular among scientists due to their rapid reproductive cycle, ease of care, and suitability for genetic manipulation. The genome of Drosophila has been fully sequenced, playing a crucial role in understanding the genetic and molecular mechanisms of many human diseases. Fruit flies are ideal models for research in neuroscience, developmental biology, and genetics, and they have significantly contributed to the scientific community.

Researchers from the University of Queensland, the University of Melbourne, and the University of Washington conducted a study, published in eLife, focusing on the sleep habits of fruit flies. A previous study published in Nature in 2021 demonstrated that sleep in fruit flies is disrupted by social isolation and that they sleep best in the presence of other flies.

This new study examines how experimentally induced active and quiet sleep in fruit flies triggers independent transcriptional programs. Sleep is generally divided into two main physiological categories: rapid eye movement (REM) sleep and slow-wave sleep (SWS). REM and SWS are two distinct types of sleep thought to fulfill different functions. But do similar sleep stages exist in Drosophila?

The study compared two methods for inducing sleep in fruit flies: first, the activation of sleep-promoting neurons with light (optogenetic activation); and second, the administration of a sleep drug called gaboxadol. Both methods showed similar effects in increasing sleep duration but had different impacts on brain activity. Gene analyses revealed that drug-induced deep sleep (‘quiet’ sleep) primarily appears to slow metabolism and regulate stress, while optogenetic ‘active’ sleep increased many genes related to normal wakefulness functions and appeared to support cognitive function.

These are just a few of the standout studies. All these scientific investigations into animal consciousness reveal that animals may possess more complex minds than we previously thought.

The New York Declaration on Animal Consciousness aims to clarify the message emerging from the research conducted over the past decade. The first goal of the declaration is to encourage more high-quality research on animal consciousness. While uncertainty persists about the nature of consciousness and which animals are “conscious,” the declaration hopes that additional studies will help reduce this uncertainty.

The second goal of the declaration is to promote greater consideration of animal welfare. If we accept that animals have conscious experiences, what changes does this require regarding their rights and welfare?

This may necessitate reevaluating our relationship with animals and how we treat them. Studies on animal consciousness have implications for our ethical and legal approaches, suggesting a need for greater emphasis on animal rights. Researchers argue that if there is a realistic possibility of consciousness (e.g., octopuses feeling pain), then this possibility deserves consideration in decisions affecting these animals, such as whether to support octopus farming.

Improving the living conditions of animals and showing them respect emerges as both an individual and a societal responsibility. With increased awareness of animal consciousness, we can take significant steps toward building a more compassionate and just world.