A little fish has sophisticated self-awareness only previously seen in humans.
A little fish has high levels of self-awareness
The finger-sized bluestreak cleaner wrasse has become the first fish to pass the "mirror test" which shows that it knows when it is looking at itself and is capable of using the reflection to compare its size to that of a predator.
Taiga Kobayashi, who led the study at Osaka Metropolitan University in Japan, told New Scientist: "Our study established cleaner fish as the first non-human animal to be demonstrated to possess private self-awareness.
"This was unexpected because we had an image that this fish always shows aggression against rivals, regardless of size.
"These findings suggest that cleaner fish would likely possess two mental states: a mental image of their body and internal standards for comparing body size."
Kobayashi continued: "The results that fish can use the mirror as a tool can help clarify the similarities between human and non-human animal self-awareness and provide important clues to elucidate how self-awareness has evolved."