What do fish see when they look in the mirror? Not themselves. Since the 1930s, studies have shown that fish will fight their own reflections. And it turns out that they hate themselves more than they hate other fish. When researchers placed African cichlid fish in a tank, the fish showed identical aggressive behavior whether their opponent was their reflection or another fish across a clear barrier, ramming and biting at both. But their brain activity differed markedly with each foe, the team reports  online today in Biology Letters. The fish facing off with their own reflections showed greater activity in an area of the brain tied to fear and negative emotional learning, which suggests they find themselves scarier than any real rival.
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