Mirror test hints at surprising cognitive abilities in fish

Thu, 2019-02-07 19:00

WASHINGTON: A small tropical reef fish was able to recognize
itself in a mirror, scientists said on Thursday in a finding that
raises provocative questions about assessing self-awareness and
cognitive abilities in animals.
The study involved experiments in which the fish species Labroides
dimidiatus, called the bluestreak cleaner wrasse, was given a
mirror self-recognition test, a technique developed in 1970 for
gauging animal self-awareness.
In aquarium experiments at Osaka City University in Japan, the
researchers applied a brown-colored mark on the fish’s body in a
place that could be seen only in a mirror reflection.
The fish tried to remove the marks by scraping their bodies on hard
surfaces after watching themselves in a mirror, but never tried to
remove them without a mirror present, indicating they understood
the reflection was of them, the researchers said. When a
transparent, rather than brown, mark was applied, the fish never
tried to remove it.
The four-inch-long (10-cm) species consumes parasites and dead
tissue off skin of other reef fish in a relationship benefiting
both. The brown mark’s color resembled the color of these
The fish “shows behaviors during the mirror test that are
accepted as evidence for self-awareness in many other species,”
said evolutionary biologist Alex Jordan of the Max Planck Institute
for Ornithology in Germany, who led the study published in the
journal PLOS Biology.
Jordan, however, questioned whether the test represents a reliable
measure of animal cognitive abilities.
“I don’t claim that fish lack self-awareness, but rather that
the minimal required explanation for the behaviors we observe in
the mirror test does not require invocation of self-awareness,
self-consciousness, or theory of mind,” Jordan said.
The test has been passed by great apes including chimpanzees,
bonobos, gorillas and orangutans as well as dolphins, killer
whales, an elephant and a magpie species, but failed by some other
animals. Humans pass it at around 18 months old.
“I consider that there is a spectrum of animal consciousness,
with some animals, likely primates, showing abilities closer to
human consciousness,” Jordan said. “My point with this paper is
not that fish are as smart as chimpanzees, but that the way we ask
that very question across taxa (animal groups) needs to be
University at Albany evolutionary psychologist Gordon Gallup, who
pioneered the mirror test, called the new study “not
methodologically sound” and faulted the researchers for a “zeal
to undermine the integrity” of the technique to appraise animal
Emory University primatologist Frans de Waal, who has studied
mirror self-recognition in mammals, called the findings
“interesting and provocative.”
“The hope is that this study will throw open the discussion about
self-awareness in animals. Instead of the black-and-white
distinction we have had thus far, that some animals have it and
most of them don’t, we need to develop a more gradualist
perspective,” de Waal said.

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Mirror test hints at surprising cognitive abilities in fish