Researchers have discovered that a small fish known as the cleaner wrasse will check its own body size before deciding whether to attack other fish or not.
The findings have been published in the journal Scientific Reports by a team at Osaka Metropolitan University in Japan.
As The Irish Examiner reports, Osaka Metropolitan University researcher Taiga Kobayashi has said that proof that fish can use the mirror as a tool can “help clarify the similarities between human and non-human animal self-awareness."
Chimpanzees, dolphins, elephants, pigeons and magpies are among a handful of species that have already pssed the mirror self-recognition (MSR) test, used for determining self-awareness.
This test involves putting paint or sticker marks on the body and placing the animals in front of the mirror to see whether they examine these marks.
Previous research has shown that cleaner wrasse can pass the MSR test, and the team wanted to know whether they can construct a mental image of their body after looking at themselves in the mirror, and then making decisions based on this mental representation.
A total of 15 cleaner fish were used in the test, seven of which had access to a mirror inside an aquarium .These fish were then presented with cut-out photos of a different group of fish that were either slightly (10%) bigger or slightly (10%) smaller.
The team found that the cleaner wrasse previously exposed to mirrors were less aggressive towards larger and same-sized fish in the photos but were more hostile towards the smaller fish.
The scientists conclude that cleaner wrasse may be capable of metacognition, as in an individual's ability to reflect on their thought process to plan and make decisions.
They suggest that further research is needed to confirm this.
Read The Irish Examiner here
