Fish passes mirror test for signs of self awareness

Fish may be self-aware, scientists have said, after the first species passed the so-called “mirror test” that demonstrates recognition of the self.

Only a few animals such as humans, apes, dolphins and some birds can recognise themselves in a mirror, and will attempt to remove marks on their skin after noticing them in the reflection.

The ability suggests a level of cognition not shown by children until they are about 18 months old.

Until now, no fish has demonstrated the ability, but experiments by the Max Planck Institute for Ornithology, show the cleaner wrasse will try to remove marks placed on its body by researchers, after viewing itself in a mirror.

Dr Alex Jordan, senior author of the study, said: “This fish behaviourally fulfils all criteria of the mirror test as originally laid out.”

The fish never tried to remove the marks when no mirror was present. Unmarked fish also did not attempt to remove marks from themselves when interacting with a marked fish on the other side of a window.

However, scientists are not sure if fish are self-aware or if the goldstandard test used to denote higher intelligence may be flawed.

Commenting on the research, Professor Frans de Waal, a primatologist at Emory University, said: “Only with a richer theory of the self and a larger test battery will we be able to determine all of the various levels of selfawareness, including where fish fit in.” The finding was published in the journal PLOS Biology.