Octopus and squid can hear. The discovery resolves a century-long debate over whether cephalopods, the group of sea creatures that includes octopus, squid, cuttlefish and nautiluses, can hear sounds underwater. Compared to fish, octopus and squid do not appear to hear particularly well. But the fact they can hear raises the possibility that these intelligent animals may use sound to catch prey, communicate with one another or listen out for predators. The question of whether cephalopods can perceive sound has been controversial since the early 20th Century. Some experiments suggested that blind octopus seemed able to locate the sounds produced...