Rethinking Consciousness and Ethics in the Animal Kingdom
of all animal species are invertebrates
of all individual animals are invertebrates
In the vast tapestry of animal life on Earth, invertebrates account for approximately 95% of all species and an astounding 99.9% of all individual animals. Yet, despite their overwhelming numerical dominance, these spineless creatures have largely been excluded from moral consideration and welfare protections.
The common perception of insects, spiders, and other invertebrates as simple biological automatons is being challenged by groundbreaking scientific discoveries that reveal sophisticated cognitive abilities and possibly even consciousness in these evolutionarily distant relatives.
The exclusion of invertebrates from moral consideration stems from what philosophers Irina Mikhalevich and Russell Powell identify as "anachronistic readings of evolution," which view invertebrates as lower in the natural hierarchy, alongside persistent assumptions that small brains cannot support cognition or sentience1 5 . As we'll discover, these assumptions are increasingly difficult to maintain in light of growing evidence that arthropods have converged on cognitive functions comparable to those found in vertebrates1 .
Philosophers and scientists have long debated what qualifies as "mindedness" in animals. According to philosopher Peter Carruthers, there are several competing theories about what constitutes a mind2 :
Some argue that language is essential for thought, but this would exclude human infants and aphasic patients from moral consideration.
Others suggest existence in a "space of reasons" subject to norms of rationality, but human reasoning often relies on quick-and-dirty heuristics.
Another view emphasizes creative concept combination, which may be unique to humans through capacities for creative supposition.
Carruthers proposes that what matters morally is not merely the capacity to feel pain, but whether a creature possesses a belief-desire psychology and is capable of having its desires frustrated2 . On this view, what makes pain morally significant is that the creature "very much wants the pain to go away, and is frustrated in this desire"2 .
We readily attribute consciousness to other humans because they share our anatomy and behavior and can describe their subjective experiences. Nonhuman mammals, with their humanlike behavior and anatomy, are also widely accepted as sentient, though Cartesian doubts remain possible. But invertebrates present a special challenge—they lack both neurological similarity to humans and the language to describe their experiences3 . This combination makes their sentience particularly difficult to assess.
Despite their small size and different neural architecture, many invertebrates display cognitive abilities that rival those of vertebrates. The tiny brains of insects, containing approximately 1 million neurons compared to our 100 billion, nevertheless facilitate sophisticated behaviors6 .
Cephalopods like octopuses exhibit exceptional problem-solving skills, memory, and even play behavior—traits typically associated with higher vertebrates6 .
With no consensus on how to determine whether invertebrates are conscious, philosopher Jonathan Birch proposes a middle path between theory-heavy and theory-neutral approaches6 . The theory-light approach centers on a minimal hypothesis: "phenomenally conscious perception of a stimulus facilitates, relative to unconscious perception, a cluster of cognitive abilities in relation to that stimulus"6 .
Instead of beginning with a complete theory of human consciousness or relying solely on behavioral analogies, this approach systematically searches for consciousness-linked cognitive abilities, their relationships to each other, and their sensitivity to masking6 . This provides a practical framework for investigating invertebrate consciousness while acknowledging the limitations of our current theories.
| Approach | Methodology | Key Challenges |
|---|---|---|
| Theory-Heavy | Apply established theories of human consciousness to animals | Theories of human consciousness are controversial and may not apply to different neural architectures |
| Theory-Neutral | Build lists of behavioral similarities and use analogical reasoning | Risks being overly permissive or restrictive without theoretical guidance |
| Theory-Light | Search for cognitive abilities linked to consciousness in humans | Requires careful study of multiple cognitive abilities and their relationships |
One of the most compelling demonstrations of complex cognition in invertebrates comes from experiments on social learning in bumblebees. This experiment revealed that these insects are capable of behaviors previously thought to be limited to vertebrates with much larger brains.
First, researcher "demonstrator" bees were trained to solve a puzzle involving an artificial flower. The flower required a specific sequence of manipulations to access a sugar solution reward.
"Observer" bees were allowed to watch the demonstrator bees successfully solve the puzzle multiple times through a transparent partition.
The observer bees were then presented with the same puzzle themselves, without any additional training or reinforcement.
A separate group of naive bees with no exposure to demonstrators was also presented with the puzzle to establish baseline solving rates.
The experiment was repeated with different puzzle configurations to determine how generalizable the learning was.
The findings were striking. Observer bees that had watched demonstrators solved the puzzle at significantly higher rates than control bees. Even more remarkably, some observer bees developed novel methods for solving the puzzle that differed from what they had observed, demonstrating cognitive flexibility rather than mere mimicry.
This experiment provides strong evidence for social learning in bumblebees—a capacity that requires sophisticated cognitive processing and was previously thought to be limited to vertebrates with much larger brains. The ability to learn through observation and then innovate upon what was learned suggests a level of cognitive flexibility that many theorists associate with conscious processing.
| Experimental Group | Puzzle Success Rate | Time to Solution | Behavioral Innovation |
|---|---|---|---|
| Observer Bees | Significantly higher | Faster | Present - developed novel approaches |
| Control Bees | Baseline low | Slower or no solution | Absent |
| Demonstrator Bees | High after training | Fast after training | Limited to learned method |
Bumblebees demonstrated not just imitation but innovation, developing novel solutions to puzzles they observed being solved.
The growing evidence for sophisticated cognition in invertebrates presents what Peter Carruthers calls "a challenge for ethical theory"2 4 . If we extend moral concern to vertebrates based on their capacity for cognition and potential for suffering, what principled reason can we give for denying similar consideration to invertebrates who demonstrate comparable cognitive abilities?
Mikhalevich and Powell argue that the exclusion of invertebrates is motivated not only by scientific uncertainty but also by cognitive-affective biases that covertly influence moral judgment1 5 . We tend to favor animals that are larger, more attractive, longer-lived, less numerous, and less disgust-provoking—biases that work systematically against invertebrates.
When scientific uncertainty exists about sentience, how should we err? Mikhalevich and Powell suggest that the same standards of evidence and risk management that justify policy protections for vertebrates also support extending moral consideration to certain invertebrates1 5 . If there's a reasonable possibility that these creatures can suffer, and we wouldn't knowingly cause suffering to them, then a precautionary approach would suggest including them within our moral circle.
| Bias Type | Description | Impact on Invertebrates |
|---|---|---|
| Aesthetic Bias | Preference for more attractive animals | Works against many insects and "creepy crawlies" |
| Size Bias | Tendency to favor larger animals | Disadvantages most invertebrates |
| Numeracy Bias | Difficulty valuing very numerous species | Affects insects and other highly populous invertebrates |
| Similarity Bias | Preference for animals similar to us | Disadvantages evolutionarily distant species |
| Disgust Response | Aversion to certain animals | Impacts worms, insects, and other "disgusting" creatures |
Research into invertebrate cognition employs several sophisticated methods to probe these tiny minds:
Carefully designed puzzles and challenges that test cognitive abilities like problem-solving, memory, and social learning.
Recording from invertebrate nervous systems to understand how their neural architecture supports complex behaviors.
Using substances like morphine to test pain pathways—research shows morphine suppresses the motivational aspect of pain in vertebrates while leaving sensory discrimination intact2 .
Testing similar cognitive abilities across diverse species to identify convergent evolutionary solutions.
Adapting methods from human consciousness research, such as backward masking, to study differences between conscious and unconscious perception6 .
The study of invertebrate minds challenges not only our scientific understanding but our ethical frameworks as well. As evidence accumulates for sophisticated cognition in everything from bees to octopuses, we're compelled to reconsider the moral boundaries we've drawn between species.
This research invites us into what philosopher Thomas Nagel called "what it is like to be" another creature—even one as alien to us as a bee or spider6 . While we may never fully comprehend the subjective experience of a creature with a radically different neural architecture, we have increasing reason to believe that there is something it is like to be them.
The project of understanding invertebrate minds is not merely an academic curiosity—it has profound practical implications for how we treat the overwhelming majority of Earth's animals. As we continue to develop a more comprehensive animal ethics, one that responds to novel scientific evidence while acknowledging the philosophical challenges, we move closer to a moral framework worthy of the complex world we inhabit.
As Mikhalevich argues, we need an ethics that responds to "these 'alien' minds on Earth"—not by excluding them from moral concern, but by recognizing their intrinsic value and potential for experiences that matter to them. In doing so, we may finally move beyond a vertebrate-centered conception of welfare that has arbitrarily limited our moral compassion.