Whether browsing a pet store or snorkeling on vacation, you may have wondered: can fish smile? At first glance, it might seem impossible. After all, their faces look so different from ours. But scientists have discovered that fish do make facial expressions, and some of them resemble human smiles and frowns.
If you’re short on time, here’s a quick answer to your question: While fish don’t have the facial musculature to make expressions like humans do, researchers have found that some species of fish can make expressions with their mouths and body language that resemble human emotion.
Certain stimuli even provoke responses in parts of a fish’s brain analogous to where emotions are processed in humans.
In this approximately 3000 word guide, we’ll dive deeper into the evidence around fish facial expressions and what they might mean. You’ll learn about scientific discoveries on how fish communicate, along with insights from experts on fish behavior and anatomy.
We’ll also explore some of the implications around recognizing fish as sensitive, communicative beings.
What Studies Reveal About Fish Facial Expressions
Fish Make Mouth Shapes Resembling Human Smiles and Frowns
Recent studies have shown that fish make distinct mouth shapes that resemble human facial expressions like smiles and frowns. Researchers at the University of Liverpool found that archerfish make different facial expressions when looking at food compared to conspecifics.
The archerfish made their lips into an “O” shape which resembled a human smile when looking at food, while they pressed their lips together in a frown-like shape when looking at other fish.
Another study from 2021 discovered that zebrafish make smile-like expressions by turning up the corners of their mouths when they are in a positive environment. These smile-like expressions were associated with the release of dopamine, suggesting an emotional response.
The researchers believe these facial expressions help zebrafish communicate positive emotions.
According to Dr. Sonja Wild, an ethologist from the University of Konstanz, “Fish do make faces”. While fish facial muscles operate differently than human ones, they appear capable of conveying basic emotional states through facial expressions.
Fish Show Emotion-Like Responses to Stimuli
In addition to making facial expressions, studies show fish demonstrate complex behaviors that suggest they experience emotion-like states. Zebrafish have been found to show signs of anxiety, reacting with alarm to frightening stimuli.
They also demonstrate curiosity and show signs of excitement when exploring new environments.
Dr. Becca Franks, an animal behavior professor at New York University, notes that fish behavior meets many of the same criteria used to identify emotions in mammals. For example, fish behavior is flexible, meaning they change their behavior based on their environment.
Their behaviors also motivate future actions, such as seeking rewards or avoiding threats.
Fish Have Specialized Brain Structures for Facial Muscles
How are fish able to make meaningful facial expressions if they don’t have faces like mammals? Research has found fish have specialized brain structures dedicated to controlling their facial muscles and conveying expression.
For example, a 2020 study discovered a region of the zebrafish brain that contains over 7,000 neurons wired to control the complex muscle movements of the fish’s mouth and jaws. This connects to facial muscles that allow zebrafish to change their mouth shape.
Other teleost fishes have sections of their hindbrain that control their facial muscles. According to Wild, this suggests that “making faces is not a trivial action for a fish.” Their brains have evolved structures dedicated to facial movement and expression.
The Evolutionary Origins of Fish Facial Expressions
Shared Evolutionary Origins With Humans
Research shows that fish facial expressions likely share an evolutionary origin with human facial expressions. Humans and fish are both vertebrates and share a common ancestor from over 420 million years ago.
This means the capacity for facial communication evolved early on and has been retained in both fish and humans over evolutionary time.
Like humans, fish faces contain important sense organs and structures used for eating and breathing. They also have muscles that allow movement to form different facial expressions. For example, tilapia have 58 individual facial muscles that allow them to create complex facial movements.
The capacity for facial communication and expression conveys evolutionary advantages. According to a 2022 study published in Proceedings of the Royal Society B, facial muscles allow fish to communicate vital information related to aggression, courtship, and responding to predators and competitors (https://royalsocietypublishing.org/doi/10.1098/rspb.2021.2599).
This type of visual communication helps with survival and reproduction.
Differences in Fish Facial Anatomy
While fish share common origins for facial expression with humans, there are also important anatomical differences:
- Fish have a more distributed nervous system, so facial expressions may originate from different neural regions compared to humans.
- Many bony fish species have rigid skulls, so their capacity for facial movement focuses more on specialized regions like the jaws, cheeks, and gill covers compared to the whole human face.
- Fish lack some musculature that humans use for facial expressions. For example, fish don’t have muscles to move their eyebrows up and down.
- Some fish species like electric eels and rays lack paired appendages, which can limit fin-related communication seen in other fish.
While fish facial anatomy has evolved differently from humans in some regards, researchers believe their faces still play a vital role in visual communication. Interpreting unique fish facial expressions offers an intriguing window into understanding their behaviors and emotional states.
| Facial Anatomy Aspect | Fish | Humans |
|---|---|---|
| Skull Rigidity | Often rigid skulls | Malleable facial bones |
| Musculature | 58 muscles in tilapia | 43 muscles in humans |
| Neural Control | Distributed nervous system | Facial expressions linked to defined brain regions |
What Do Fish Facial Expressions Communicate?
Indicating Stress, Excitement and More
Studies show that fish do make facial expressions to communicate different emotional states. For example, when a fish is stressed or afraid, its eyes may appear larger and more rounded as a way to take in more visual information.
On the other hand, excited or aggressive fish often flare out their gill covers to appear bigger. This signals dominance or readiness to fight.
According to researchers at the University of Liverpool, fish also show more subtle expressions around their eyes and mouth to indicate more nuanced emotions. Increased eye swelling and quicker mouth movements can signal higher stress or alertness.
More relaxed fish exhibit smaller eyes and slower jaw movements. Detecting these signs can help better understand and meet the welfare needs of fish in human care.
Communication Between Fish
Fish don’t just make facial expressions randomly – often, the displays are used to communicate with other fish. For example, when defending a territory from intruders, a fish may flare its fins or gills to signal aggression and scare others away.
Male fish also use facial cues like swollen jaws during mating displays to attract potential female partners.
According to animal behavior studies, fish can even recognize other specific individual fish based on their characteristic facial features and color patterns. This shows that fish are capable of more complex social interaction and communication than previously thought.
Their facial signals likely convey a variety of information beyond just aggression and courtship.
Responses to Environmental Stimuli
Aside from social communication, fish facial movements also serve as reflexive responses to smells, tastes, temperatures, and other stimuli from their external environment. These involuntary expressions can provide insight into a fish’s moment-to-moment experience in its aquatic habitat.
For example, upon tasting desirable food or scent cues, the facial muscles around a fish’s mouth will activate to begin feeding behavior – similar to the involuntary response when humans smell something delicious.
Fish may also make defensive expressions like widening their eyes or mouths when confronted by sudden bright lights, loud noises, or unfamiliar objects in their enclosures.
Noting these reflexive fish “facial” reactions to stimuli gives aquarists and researchers indications of the captive fish health and wellbeing at a precise moment. Monitoring fish faces can help ensure their environments provide a low-stress, engaging experience.
Facial Recognition and Emotional Lives of Fish
Evidence for Complex Inner Lives
Recent studies provide mounting evidence that fish possess surprisingly complex inner lives. Facial recognition research shows that fish can distinguish between individuals by subtle differences in facial characteristics.
In one experiment, archerfish were trained to spit at images of particular fish faces when prompted. The archerfish demonstrated an ability to recognize faces of fish they knew, compared to unfamiliar fish (Newport et al., 2021).
Further evidence comes from studies exploring emotional states in fish. Stress levels in zebrafish were measured when exposed to threatening stimuli. Zebrafish showed elevated cortisol levels and greater erratic movement when presented with a simulated predatorial threat, compared to a non-threatening stimulus (Speedie & Gerlai, 2008).
This suggests zebrafish have some capacity for emotional arousal.
Cleaner wrasse fish provide a particularly striking example of complex social behavior. They appear to understand cooperation, cheating, and reconciliation – their helping behaviors follow calculated rules to optimize outcomes (Bshary & Grutter, 2002).
Such strategic social maneuvering implies a strong intellect. As Bshary and Grutter (2002) state: “It takes two to tango – even for fish! “
Implications for Fish Welfare
The inner lives of fish have welfare implications. If fish are sentient beings capable of experiencing positive and negative emotional states, this ethically compels us to ensure humane treatment of farmed and wild fish.
However, the commercial fishing industry largely disregards fish sentience. Common angling practices often inflict intense stress, exhaustion and physical injury on fish. And overcrowded aquaculture pens restrict natural behaviors, denying fish the ability to thrive (Huntingford et al., 2021).
Fortunately, reforms are underway. Novel tracking tools enable comparison of stress levels across aquaculture environments, identifying optimal stocking densities and systems design (rollo et al., 2021).
And the development of humane slaughter methods, such as electric or percussive stunning, can minimize suffering at death. However, continued research into fish sentience and welfare is essential to inform evidence-based reforms.
Unanswered Questions and Next Steps in Research
While exciting advancements have been made in understanding fish facial expressions, many questions remain unresolved. Researchers are still working to decipher the full range of fish emotions and what subtle variations in facial muscles may communicate.
There is also much to learn regarding how factors like environment, social dynamics, and human intervention impact fish emotion and expression.
Quantifying Complex Emotions
To date, most research has focused on identifying basic emotional states like fear, aggression, or pleasure. However, fish may experience far more nuanced and complex emotions that have yet to be quantified. Do fish feel complex social emotions like jealousy, empathy or love?
How do emotions differ between various species and what significance might minute muscular differences hold?Fish likely experience a panoply of feelings that science is only beginning to grasp.
Environmental and Social Impacts
Researchers are interested in how environment, social dynamics, and human activity affect fish facial muscle usage and emotional state. For example, how do captive versus wild settings impact expression? Do dominant fish emote differently than subordinates?
And importantly, how do common fishing and aquaculture practices influence emotions? Understanding such impacts could meaningfully inform ethical fishing and fish farming protocols.
Cross-Species Communication Possibilities
Perhaps the most intriguing opportunity is exploring if humans could learn to “read” fish facial expressions, essentially achieving cross-species communication. Researchers speculate that with enough study, subtle differences in muscular activation could form a comprehensive “vocabulary” of fish emotion.
If humans could learn this language, captive fish could nonverbally communicate feelings like pain, fear or distress regarding environmental conditions. Mastering this ability would revolutionize animal welfare and profoundly reshape human-fish dynamics.
| Key Unanswered Questions | Potential Research Approaches |
| – Full emotional range of fish | – Monitoring facial muscle movements |
| – Impacts of environment/captivity on emotion | – Comparing wild & captive fish expressions |
| – Nuances of social fish communication | – Recording interactions of fish groups |
| – Possibilities for cross-species understanding | – Cataloging/decoding muscle variations |
Clearly, the science of fish facial expressions remains wide open with great potential to reveal surprising new insights about our aquatic cousins. As emotion decoding and ethology technology improves, researchers are extremely enthusiastic about advancing this burgeoning field.
Such progress could profoundly impact animal welfare policies, aquaculture practices and even interspecies relationships.
Conclusion
While fish don’t smile in precisely the same way humans do, scientific evidence shows they have evolved complex forms of facial communication. Researchers have identified fish facial expressions corresponding with stressful and pleasant situations.
And parts of fish brains are analogously wired to process emotions.
Understanding fish as sensitive beings with their own ways of expressing themselves could transform how we interact with them. Future research will continue uncovering the nuances of fish facial expressions and cognition.
But what we know already challenges old notions of fish as primitive, unfeeling animals. Perhaps the next time you see an aquatic creature open its mouth, you’ll wonder if it’s smiling back.
