Fish Can Detect Fear in Others, Study Finds.

A new study published in the journal Science shows that fish can detect fear in other fish and become afraid too, and this ability is regulated by oxytocin, the same brain chemical that underlies the capacity for empathy in humans. The study also showed that zebrafish will pay more attention to fish that have previously been stressed out, a behavior the researchers likened to consoling them. The research illustrates the ancestral role of oxytocin in transmitting emotion, which may have already been in place around 450 million years ago when fish and mammals last had a common ancestor.