A diminutive aquatic creature has exhibited a substantial degree of cognitive ability during investigations involving mirror tests. This fish not only demonstrated recognition of its own reflection but also employed a morsel of sustenance to probe the reflective phenomenon.
The mirror mark test serves as a standardized scientific protocol for assessing self-recognition in animals, aiming to quantify the extent to which the intelligence of other species approximates our own.
The act of retouching smudged eyeliner upon observing one’s likeness in a mirror is a clear indicator of self-awareness. An individual comprehends that a blemish on their visage is misplaced and can utilize the reflection as a reference point to precisely identify the location requiring correction.
In principle, a behavioral response to an anomalous marking on one’s reflection is presumed to signify self-recognition in other animal species as well. Among those that have successfully navigated this mark test, often considered a benchmark for intelligence comparable to human levels, are chimpanzees, elephants, and dolphins.
The cleaner wrasse (Labroides dimidiatus), a marine fish approximately finger-sized, derives its moniker from its habit of consuming parasites and necrotic tissue from larger fish. Its capacity to pass the mirror test was initially documented in 2018.
It is not difficult to surmise why the cleaner wrasse would be considered a viable subject for such research. Its primary ecological function involves removing detritus from other fish, suggesting that if it perceived a parasite-like mark on its own body, it might be similarly driven to employ the mirror for a self-directed grooming action.
Although the 2018 study indicated that the fish had succeeded in the test, the progenitor of the mirror mark test, evolutionary psychologist Gordon Gallup, conveyed to New Scientist his conviction that the fish in those experimental conditions were misinterpreting the marks on their own bodies as external parasites affecting other fish.
Subsequently, a collaborative research unit from Osaka Metropolitan University in Japan and the University of Neuchâtel in Switzerland has refined the experimental methodology to further investigate the wrasse’s level of self-awareness.
“In preceding investigations of cleaner wrasse mirror behavior, the typical protocol involved exposing the fish to a mirror for several days, allowing them to acclimate and cease social responses, followed by the application of a mark,” elucidates Shumpei Sogawa, an animal behaviorist affiliated with Osaka Metropolitan University in Japan, as detailed in a university announcement.
“In the present study, the sequence was inverted; the fish were first marked, and then the mirror was introduced. It is probable that the fish were cognizant of an anomaly on their corporeal form, yet unable to visually ascertain it. Upon the introduction of the mirror, it promptly furnished visual data that corresponded with a pre-existing somatic sensation, thus accelerating the scraping behavior.”
While this modification does not represent an entirely flawless control, it significantly enhances the foundational experimental design by affording the fish the opportunity to identify the ‘parasite’ on its own body prior to encountering its reflection.
The scientists expressed astonishment at the rapidity of the fish’s response in these novel experimental conditions; on average, they attempted to dislodge the ‘parasite’ within approximately 82 minutes. This observation, according to the researchers, suggests the presence of self-awareness preceding exposure to the mirror.
Following a period of several days wherein the fish became accustomed to the mirror, the researchers observed some individuals engaging in a peculiar behavior. These fish would retrieve a small segment of shrimp from the tank floor, convey it to the mirror, and then release it.
As the mirrored shrimp descended in tandem with the actual object, the fish intently followed their reflection, making contact with the mirror’s surface using their oral appendages.
Sogawa and his research associates posit that this behavior represents the fish’s method of investigating the mirror’s properties, utilizing an external object to gain a more profound understanding of how corresponding visual representations function.
This form of ‘contingency testing’ and the utilization of the mirror as a tool have been documented in several other species that did not pass the mark-based mirror test, including pigs, rhesus monkeys, manta rays, and corvids.
“The implications of these experimental outcomes are likely to extend beyond academic discourse, encompassing revisions to evolutionary theory and the conceptualization of self, while also exerting a direct influence on practical domains such as animal welfare, biomedical research, and even the field of artificial intelligence studies,” according to biologist Masanori Kohda, who participated in both this recent investigation and the initial publication concerning cleaner wrasse self-recognition, as cited in a university press release.
The research team suggests that these findings indicate self-awareness, a trait once believed to be exclusive to great apes, is in fact a cognitive faculty that may have emerged in a considerably broader spectrum of the animal kingdom, including fish.
“Our findings suggest that self-awareness evolved at the very least with the advent of bony fishes (approximately 450 million years ago) and is likely prevalent across the vertebrate lineage,” the researchers state in their publication.
