like you or I can when wearing polarising sunglasses – but they cannot conjure colours out of combinations of wavelength. The same colour blindness is true for the light-sensitive cells embedded throughout their skin: it turns out that octopuses can ‘see’ with their skin, as well as with their eyes. Added to this, octopus chromatophore control is thought to be ‘open-loop’, meaning that the neurons in the chromatophore lobe do not generate any obvious internal copy of the signals sent out to the chromatophores in the skin. The central brain might not even know what its skin is doing.
