Polarization contrast vision in Octopus

While the ability to analyze polarized light is widespread among animals, its contribution to form vision has not yet been documented. We tested the hypothesis that polarization vision can be used for object discrimination, by training octopuses to distinguish between targets on the basis of the presence or absence of a pattern produced by a 90° polarization contrast within the target. Octopuses recognized a 90° contrast pattern within a single target, when presented either on a horizontal/vertical axis or on a 45°/135° axis. They were able to transfer their learning to new situations and to detect a polarization contrast when the orientations of the e-vector of light passing through the target center and background differed by as little as 20°. Polarization vision may provide information similar to that available from color vision and thus serve to enhance the detection and recognition of objects.