Can Fish Recognize Themselves in a Mirror (CER)

fish worksheet

How do you know if an animal can recognize itself in a mirror? Scientists have performed many experiments to answer this question. These self-recognition tests involve placing a mark on an animal that can be viewed in a mirror. If the animal responds by trying to touch or remove the mark on themselves, it is evidence for self-awareness. The mirror test is a method used to determine whether an animal possesses the ability of visual self-recognition, which is considered a marker of self-awareness.

This short activity explores research on cleaner wrasse fish. The full study can be accessed on PLOS Biology. Fish seem an unlikely animal to be self-aware, but evidence shows that these little fish can recognize themselves in a mirror.

I’ve reduced the amount of information for students and focused simply on the way the test was conducted and the outcome. The data shows that fish will scrape their body on a substrate when they see a mark in the mirror.

fish mirror test

The data includes several controls to eliminate other variables, such as the fish feeling the mark and responding to that sense, rather than seeing it in the mirror.

Students read about the study and examine the data. Then they complete questions following a CER format (Claim, Evidence, Reasoning). The claim is that fish do exhibit self awareness because they respond to changes on their body that they view in a mirror (reasoning). Evidence from the graph shows that scraping behavior only occurs when the mark is visible in the mirror, so fish aren’t responding to the sensation.

Self awareness is one aspect of animal behavior that is often explored in Ecology, where chapters on behavior explore nature vs nurture.

Follow-Up Activities

For a lively class discussion, follow up with several other self-awareness questions:

  • How would you test other animals? *
  • Why is self-awareness important?
  • Is this behavior learned behavior or is it genetic?
  • How early do humans exhibit self-awareness?
  • Can wrasse fish recognize themselves in photographs?**

* Elephants have been studied extensively, using the same techniques. You can find research on elephant self-awareness at PNAS.

**Another study shows photographs of fish with a mark on them, those fish also exhibit scraping behavior. This suggest that wrasse fish can even recognize photos of themselves! You can access this study plus a video of the fish at PNAS.