Visual Acuity in Octopus Pallidus and Octopus Australis

Specimens of Octopus pallidus and 0. australis were trained to discriminate vertical from horizontal rectangles, vertical from horizontal gratings, and vertical and horizontal gratings from uniform grey. In the discriminations that involved gratings a conditional simultaneous discrimination procedure was used, in which the two stimuli to be discriminated were presented stationary at the two ends of the tank, and a moving white disc was shown in front of each of them. Attacks on a disc were then rewarded or punished depending on the background against which it was shown. Animals rapidly reached performance levels of better than 80% correct responses on all discriminations.