These fish are called cleaner wrasse (pronounced RAS), Labroides dimidiatus. They swim everywhere from the Red Sea to the coral reefs of French Polynesia. If I may overly personify for a bit, they’re scrappy little fellas with the capacity for advanced social behavior. You see, cleaner wrasse eat parasites that reside on other fish species. To pluck the small brown parasites and dead skin off of very large fish, you have to be charming or at least clever. Cleaner wrasse have demonstrated the ability to recognize old “client” fish from new comers. They’re also capable of determining what is or isn’t known by other conspecifics. 

And in Kohda et al.’s 2019 original research article, they are joining the ranks of other organisms who passed the MSR test. The smarty-pants club includes animals like elephants, dolphins, horses, magpies, higher apes, and two-year old humans, though some more stringent test administrators limit the admittance to chimpanzees and humans. 

Kohda and other authors in the Jordan laboratory reported these results to PLoS Biology for publication in July 2018. In January 2019, they were published in a paper titled If a fish can pass the mark test, what are the implications for consciousness and self-awareness testing in animals. It’s purely speculation, but since the Kohda paper was submitted to the PLoS Biology journal in July 2018 and not accepted or published until 2019, there might have been a hell of a lot of back and forth between the editors and researchers. This might be because the stalwart king of primate research, Frans de Waal, presides on the editorial board. After a life time of advocating for proper interpretations of animal cognitive research, Dr. de Waal was presented evidence that where monkeys, pigs, dogs, pandas, and parrots had all failed to pass the three stages of MSR… A fish past the mirror self-recognition test.

The authors go on to clarify that they’re not banging on the door to the Self-Recognition Club, demanding fish admittance. In fact, they don’t believe their findings “should be taken as evidence of self-awareness in the cleaner wrasse.” Instead, they take the hair of ‘self-awareness’ and split it into 1) a theory of mind called self-awareness and 2) observation of the physical self and perceiving it as part of the body of the observer.

Here’s a clumsy analogy: suppose an animal’s view of their body is blocked, accept for their tail protruding from the other side of the obstruction. The animal’s recognition of their tail as part of themselves, wouldn’t be theory of mind. Recognition of the tail or viewing oneself in the mirror would just be a form of incorporeal proprioception, connecting a visual input or a reflection with one’s body.

The fish scraping behavior is as self-directed as it can get in non-armed or -legged animals. And hey, if scraping behavior was good enough for everyone’s favorite sexy marine mammal, the dolphin, then saying it’s not good enough for fish would be “taxonomically chauvinistic” according to Kodah et al. Strengthening their finding’s bulwarks, they said resistance to their findings would “risk introducing subjective taxonomic biases, setting moving goal posts and precluding scientific comparisons among certain taxa.” These fish succeeded alongside other taxa in a behavioral arena heavily populated by mammals. Their little ‘o’ mouths charged their doubters of bearing the label of ‘anti-fish fascists’… … fishcists. 

Frans B.M. de Waal penned a primer to accompany the issue with the fish paper. In it, he gave ground by pointing out that the mark test is currently binary and suggested the need for “a more gradualist model of how animals construe the self and respond to mirrors” (de Waal, 2019). He then began slashing at the methodology and conclusions of Kohda et al.

Kohda et al. had equated the mirror adjacent abnormal behaviors with self-recognition, while de Waal saw this and other conclusions as “generous interpretations”. As quantified, de Waal was unconvinced these observations indicated the fish knowingly played with their own reflections.

De Waal believes these findings “suggests a more intermediate level of mirror understanding.” Even Gallup, who invented the MSR test using chimpanzees in 1970, was pulled out of cryostasis to write an article dissecting the continually flawed interpretations and applications of his test (Gallup, 2020). 

Kohda et al. 2022 Escape From the Planet of the Apes

Kohda et al. assiduously clapped back with an updated article presenting “further evidence” in February (2022). They ran a myriad of new tests where they “reiterate the conclusion of the previous study that either self-awareness in animals [YA BITCHES] or the validity of the mirror test need to be revised.” (Emphasis and “YA BITCHES” added).

“In no case is an animal activity to be interpreted in terms of higher psychological processes if it can be fairly interpreted in terms of processes which stand lower in the scale of psychological evolution and development.”

~C. Lloyd Morgan~

With the canon of the 19th-century psychologist C. Lloyd Morgan in mind, Kohda et al. addressed as many criticisms lobbed at them and then some, in their new publication. This included, but was not limited to:

1) They increased their sample size of fish and all mirror experienced fish attempted to scrape the fake parasite.

2) They diversified the implant colors. Critics found the evidence in the original Kohda et al. paper showing that clear injections did not increase scraping behavior unconvincing, perhaps because of the small sample size. One sticking point was that marks made on the fish could have a physical sensation that made them more salient than a truly tactile-less mark. If so, this sensation could drive the investigation and recognition of the mark in the mirror.  So, you know what Kohda et al. did? Yellow and blue as well as the ecologically relevant black/brown were now included in the study! Wrasses only scraped if it was the ecologically relevant brown color…. Wait, what’s the opsins expressed by these fish?… NEVER MIND! I’ve already read four papers on this subject, I’m not reading anymore!*

3) To further their evidence of marks being non-tactile, a group of wrasse received deeper implants. The deep marks made every fish itch, suggesting the superficial marks must not bother the animals enough to scrape. It’s the visual cue that’s necessary.So, get out of here with your criticism based on a rhesus macaque study with the electrophysiology head implants (Rajala et al., 2010)! Those implants were highly invasive and the study had only four subjects!

4) De Waal had postulated that the fish might believe their reflection is another individual who has a parasite mark. Like when you see someone with spinach in their teeth and you check your own, maybe seeing the mark triggers mark-area related behavior. In the new experiments, the mirror experienced fish were presented with other wrasse with markings. It didn’t initiate scrapping.

5) They, chant with me now, Moved! That! Mirror! If the mirror is moved to a different location, will the fish realize it’s still themselves or behave like a stupid macaque, unaware of spatial contingencies? Well, wrasse didn’t start attacking the newly moved mirror, out-preforming dumb old macaques (personal note, I hate macaques)!