Mantis shrimp have 16 types of photoreceptor cells compared to 3 in human eyes, but a 2014 study published in Current Biology found they correctly discriminated colors only 36% better than random chance when wavelengths were 25nm apart, a performance far worse than human color vision. The viral claim that mantis shrimp see a richer, more colorful world than humans gets the biology exactly backwards.
The Viral Claim: 16 Photoreceptors, 16 Times the Colors
Somewhere around 2013, a popular webcomic published a strip about mantis shrimp that described their 16 photoreceptor types as granting them access to a visual world unimaginably richer than anything humans experience. The strip went viral. It has been shared millions of times. Science educators repeated it. Social media amplified it. A fact about photoreceptor count got transformed into a claim about color experience, and that transformation turned an accurate anatomical observation into one of the most persistent myths in popular biology.
The underlying anatomical fact is real. Mantis shrimp (stomatopods, particularly the peacock mantis shrimp Odontodactylus scyllarus) do have 16 types of photoreceptor cells in their eyes. Humans have 3 types of cone photoreceptors. The logical leap the myth makes is that more photoreceptor types equals a richer or more detailed color experience. That leap is wrong, and the science showing it is wrong has been published and peer-reviewed for over a decade.
What the 2014 Discrimination Test Actually Showed
Hanne Thoen and colleagues at the University of Queensland published a controlled behavioral study in Current Biology in 2014, titled “A Different Form of Color Vision in Mantis Shrimp.” Their methodology was direct: they trained mantis shrimp to associate a particular color with a food reward, then tested whether the animals could distinguish that color from other colors at varying wavelength separations.
The results were striking and counterintuitive. When wavelengths were separated by just 1 to 5 nanometers, mantis shrimp performed at chance level, meaning they could not discriminate those colors at all. Even at 25nm separation, performance was only marginally above chance. Humans, with 3 cone types, routinely distinguish colors separated by 1nm or less. The animal with 16 photoreceptor types was being outperformed at color discrimination by an animal with 3.
This is not a small footnote. It is the central finding of the best behavioral study on mantis shrimp color vision to date, and it directly contradicts the viral claim in every meaningful way.
| Feature | Humans | Mantis Shrimp |
|---|---|---|
| Photoreceptor types | 3 cone types | 16 types |
| Spectral range covered | ~380nm to ~700nm (visible) | ~300nm to ~720nm (UV to near-IR) |
| Minimum discriminable wavelength difference | ~1nm | ~25nm |
| Color coding mechanism | Opponent-process (comparisons) | Spectral filter / barcode system |
| UV sensitivity | No (crystalline lens blocks UV) | Yes (4 UV receptor types) |
| Circular polarization detection | No | Yes (unique among animals) |
How Human Color Vision Works: Opponent Processing
To understand why mantis shrimp underperform at color discrimination despite more photoreceptors, you need to understand what makes human color vision so powerful. Human color perception does not simply read three independent channel outputs. The brain runs a comparison process called opponent-process color coding, a model first proposed by Ewald Hering in 1878 and confirmed neurophysiologically in the mid-20th century.
In opponent processing, the outputs of the three cone types (short-wavelength, medium-wavelength, and long-wavelength) are compared against each other. The brain generates difference signals: red vs. green (L-M), blue vs. yellow (S vs. L+M), and light vs. dark (luminance). These difference channels are analog, continuous, and the brain reads them as gradations. Even tiny differences in wavelength shift the balance of cone activation, and the brain detects that shift. This is why humans can detect a 1nm wavelength difference under optimal conditions, a resolution that requires only 3 receptor types because the computation extracting color information from those 3 types is powerful.
The key insight: color discrimination depends on the neural computation applied to photoreceptor outputs, not simply the number of receptor types. More inputs only help if the brain is set up to compare those inputs against each other.
How Mantis Shrimp Color Vision Works: The Spectral Barcode
The leading hypothesis from the Thoen et al. study, supported by subsequent modeling work, is that mantis shrimp use their 16 receptor types not as inputs into an opponent-process comparison, but as a parallel bank of narrow spectral filters. Each receptor type has a narrow tuning curve and fires when its specific wavelength band is present. Instead of comparing receptor outputs against each other, the brain reads which filters are active, essentially scanning a spectral barcode.
This system does something human color vision cannot: it performs extremely fast spectral identification without complex neural computation. A mantis shrimp does not need to compute “this is more red-shifted than that,” it simply reads “receptor band 7 is firing, receptor band 8 is not.” The identification is categorical and instantaneous. The cost is resolution within any given spectral region, since no fine comparison is happening. The benefit is speed and reliability in a noisy visual environment.
The reef environment where mantis shrimp live is characterized by dynamic lighting, high turbidity, motion, and an enormous number of competing visual targets. A color recognition system that operates like rapid barcode scanning rather than fine gradation comparison may be far better suited to that context than human-style opponent processing would be.
What Mantis Shrimp Vision IS Actually Extraordinary At
The debunking of the “richer color experience” myth should not obscure the genuine and remarkable features of mantis shrimp vision. Several of these are legitimately without parallel in the animal kingdom.
Ultraviolet Vision
Mantis shrimp have 4 receptor types tuned to ultraviolet wavelengths, spanning roughly 300nm to 400nm. Human lenses block UV light completely. Mantis shrimp use UV detection for mate selection (many stomatopods have UV-reflective markings visible only to UV-sensitive eyes) and for hunting (certain prey items are UV-reflective against UV-absorbing reef backgrounds).
Circular Polarization Sensitivity
This is the most genuinely unique feature of mantis shrimp vision. Most animals, including humans, can detect linear polarization to varying degrees. Circular polarization, in which the plane of polarization rotates as the wave propagates, is detected by almost no animals at all. Mantis shrimp detect circular polarization and have markings on their bodies that reflect circularly polarized light, creating a private signaling channel invisible to virtually all predators and competing species. This circular polarization communication system has no known parallel in the animal kingdom.
Trinocular Vision in Each Eye
Each mantis shrimp eye has three distinct scan regions, each with its own set of photoreceptors and each capable of forming an independent image. This gives each eye a form of depth perception on its own, independent of the other eye. The mantis shrimp can accurately judge distance with a single eye by comparing the images from its three scan rows, which is why it can strike prey with lethal precision using only monocular information.
Why Did They Evolve 16 Types If Not for Richness?
Evolution does not optimize for richness of subjective experience. It optimizes for survival and reproduction. The 16 receptor types in mantis shrimp vision appear to be an evolutionary solution to the specific demands of reef predation and stomatopod social signaling. The spectral barcode system allows rapid, reliable color categorization under the turbulent, dynamic lighting conditions of coral reef environments. Fast prey identification, fast threat assessment, and fast intraspecific signaling are all more adaptive in that environment than fine-grained color discrimination.
The 16 types also span a spectral range from UV to near-infrared, covering wavelength regions that human vision entirely misses. This gives mantis shrimp access to information channels in their environment that human eyes cannot even perceive, including the UV-reflective markings of conspecifics and prey, and circularly polarized light signals in reef environments. This is a different kind of visual superiority than “seeing more colors” but it is genuine and significant.
Just as the bombardier beetle’s chemical defense system is extraordinary for what it actually does rather than what myths claim, mantis shrimp vision is remarkable precisely where the science confirms it, not where viral simplification invented capabilities it does not have.
How the Myth Spread and Why It Stuck
The sequence of events behind the mantis shrimp myth is a case study in how accurate science gets distorted through progressive simplification. Marshall et al. published accurate anatomical work on stomatopod photoreceptors in 1996, correctly noting 16 types and their spectral ranges. Science writers then reported this accurately for years. The claim “mantis shrimp have 16 photoreceptor types vs. human 3” was always true.
The distortion happened at the translation step, when a popular webcomic circa 2013 extrapolated “more photoreceptors” into “richer visual experience.” The original comic was created with genuine enthusiasm for science and included no malicious intent, but the leap from “more receptor types” to “sees more colors” is scientifically incorrect and the comic’s viral reach cemented the incorrect version into popular consciousness far more effectively than any correction has managed since.
This same pattern appears across popular science. The Bajau people’s underwater vision adaptation is another case where a genuine biological phenomenon gets amplified into claims that outrun the actual evidence. The pattern is consistent: an accurate finding gets simplified for accessibility, the simplification introduces an error, and the error spreads faster than the correction because it is more emotionally resonant and shareable.
The behavioral evidence from Thoen et al. 2014 has been widely discussed in the scientific press, but the viral comic continues to be shared. Corrections rarely achieve the reach of original viral content. For anyone drawn to unusual animal biology, capybara social behavior offers another example of how the accurate story is often just as interesting as the mythologized version, without requiring distortion.
FAQ: Mantis Shrimp Vision Explained
Can mantis shrimp see more colors than humans?
No. Despite having 16 photoreceptor types compared to human 3, mantis shrimp discriminate colors significantly worse than humans. A 2014 Current Biology study found they could not reliably distinguish colors separated by less than 25nm, while humans can distinguish colors just 1nm apart. They see a broader spectral range (including UV) but with less color discrimination resolution.
How many colors can a mantis shrimp actually see?
Mantis shrimp do not appear to see more discrete colors than humans in the way that question implies. Their 16 receptor types function as a spectral barcode system, categorizing colors quickly rather than discriminating fine gradations. Humans with 3 cone types and opponent-process neural coding can distinguish approximately 10 million color variations. Mantis shrimp likely distinguish far fewer.
What are mantis shrimp photoreceptors actually used for?
The 16 receptor types allow rapid spectral identification (barcode-style color recognition), UV detection for mate and prey identification, and coverage of a broader wavelength spectrum than human vision. The system is optimized for speed and reliability in chaotic reef environments, not for fine-grained color discrimination. Circular polarization detection is an additional function unique to stomatopods.
What animal actually has the best color vision?
By color discrimination resolution, humans and other trichromatic primates perform extremely well. Some butterfly species have 5 or more photoreceptor types with opponent-process coding that may give genuinely superior color discrimination. For breadth of spectral detection including UV and polarization channels, stomatopods cover more of the electromagnetic spectrum but with lower discrimination precision within each region.
Is the 2014 mantis shrimp study the final word?
Thoen et al. 2014 is the most rigorous behavioral study on mantis shrimp color discrimination published to date and its findings have not been contradicted by subsequent research. The spectral barcode hypothesis remains the leading mechanistic model. Further work on neural processing in stomatopods may refine the picture, but the core conclusion that mantis shrimp do not see “more colors” than humans is well-supported.
What This Means for How You Read Science News
The mantis shrimp vision story is worth holding onto as a reference point. The next time a viral science claim leads with “X has more Y than humans, so it experiences Z more richly,” apply the same scrutiny that the Thoen lab applied. More receptors, more neurons, more connections do not automatically translate into richer experience. The architecture of the system and the computations applied to its outputs matter at least as much as the raw count of inputs.
Mantis shrimp remain genuinely extraordinary animals. Their strike speed (the peacock mantis shrimp can accelerate its dactyl clubs to 23 meters per second, generating cavitation bubbles that strike prey even when the clubs miss), their circular polarization communication, their trinocular depth perception, and their UV signaling systems are all real and all remarkable. The actual biology is worth more than a myth built on a misread of a receptor count.
For a broader look at how pharmacological and biological systems can be misunderstood through simplified popular accounts, see the full archive at DLMethod.com, where every claim links to the primary source that supports it.