Self-Awareness Test Passed by a Fish

One of the indicators that scientists use to measure evolutionary development is a test that determines whether an animal has an awareness of itself. The test involves placing a mirror in front of the organism and then observing the animal to see if it gives evidence that it recognizes that what it sees in the mirror is an image of itself. A recent report says that a fish can pass this self-awareness test.

Self-awareness has been used to categorize animals as having higher intelligence than others. Scientists have considered the mirror test to be the “gold standard.” Applying that test they have determined that great apes, bottlenose dolphins, killer whales, Eurasian magpies, and Asian elephants are all very intelligent and therefore highly evolved. Now a fish known as the cleaner wrasse passes the self-awareness test and must be added to the list.

Researchers in Germany placed a mark on the four-inch fish in a location that could only be seen in a mirror. The cleaner wrasses checked their reflection multiple times and then tried to remove the mark by rubbing their bodies on hard surfaces. With no mirrors, the fish didn’t try to remove the mark. When the mark was placed on the mirror, the fish ignored it.

We should note that the cleaner wrasse survives by inspecting larger fish for parasites and dead tissue. The larger fish waits patiently while the wrasse cleans it by eating what it finds. This mutual relationship protects the health of the larger fish while providing food for the wrasse. Symbiotic relationships like that can be more easily explained by design than by evolutionary theory. Since the wrasse is designed to look for unwanted detritus on the bodies of other fish, perhaps that is why it is keen to notice marks on its own body.

If self-awareness shows high intelligence, we must now add a fish to the list of intelligent mammals and birds. Dr. Alex Jordan reported that the fish “behaviorally fulfills all criteria of the mirror test.” Dr. Jordan says that either the species is self-aware or the gold standard test needs updating.

–John N. Clayton and Roland Earnst

Reference: The Week, March 1, 2019, page 20.