Researchers have found that bluestreak cleaner wrasse (Labroides dimidiatus) look at their size in a mirror before deciding whether to attack other fish that are either a bit larger or smaller than them. This marks a significant discovery, as it suggests that a non-human animal can exhibit some mental states related to private self-awareness.
What if the fish had its own reflection to consider? Would that influence its behavior? According to a research team from Osaka Metropolitan University, the answer is yes.
In a study published in Scientific Reports, the researchers claimed that it’s the first evidence showing a non-human animal, specifically the bluestreak cleaner wrasse (Labroides dimidiatus), displaying mental states such as body image, standards, intentions, and goals—elements associated with private self-awareness. These fish examined their size in a mirror before deciding whether to strike at fish slightly larger or smaller than themselves.
The research team included graduate student Taiga Kobayashi, Specially Appointed Professor Masanori Kohda, Professor Satoshi Awata, Specially Appointed Researcher Shumpei Sogawa, and Professor Redouan Bshary from the University of Neuchâtel in Switzerland. Last year, they discovered that the cleaner wrasse could recognize itself in photographs by identifying its facial features through mirror self-recognition.
In this new study, the wrasse’s behavior of regularly checking its reflection suggested that the fish was using the mirror to compare its size to that of other fish and anticipate the results of potential confrontations.
“Our findings indicate that fish can utilize mirrors as tools, helping to clarify the connections between human and animal self-awareness, and providing vital insights into how self-awareness may have evolved,” stated doctoral candidate Kobayashi.
This research received funding from JST SPRING (JPMJSP2139 to T.K.), JSPS KAKENHI (23KJ1829 to T.K., 19F19713 and 20K20630 to M.K., 22H02703 to S.A., and 20K20154 to S.S.), the Swiss Science Foundation (310030_192673 to R.B.), and an OCU Strategic Research Grant for 2018-2019 (to M.K. and S.A.).
