A cleaner wrasse interacts with its reflection in a mirror. A study, which suggests that fish might possess far higher cognitive powers than previously thought, has ignited an intense debate over how we assess the intelligence of animals

Do fish really possess higher cognitive powers?

Mirror self-recognition test

The standard method for testing whether an animal is self-aware is placing a mark on its body that cannot be viewed directly and then letting it have a look in a mirror. If the animal responds to its reflection and attempts to remove the mark it is considered evidence that the animal is self-aware.