 Bigfin reef squids and the common octopus ( Octopus vulgaris ) were studied to resolve a century @-@ long debate over whether cephalopods can hear . Unlike fishes , cephalopods do not possess air @-@ filled swim bladders , which might amplify sound waves travelling in water . The results were published in 2009 . It showed that bigfin reef squids and octopuses utilise their statocysts for detecting vibrations , an organ primarily used for maintaining spatial orientation . The common octopus can hear sounds between 400 Hz and 1000 Hz . Bigfin reef squids have a slightly better hearing range of 400 Hz to 1500 Hz . Both hear best at a frequency of 600 Hz . Relatively , their hearing is comparable to prawns and some other invertebrates but is less sensitive than that of most fishes . 
