Cuttlefish viewing a movie of shrimp through 3D glasses properly positioned themselves to strike the "prey," suggesting these cephalopods hunt using a process called "stereopsis" to calculate depth based on the distance between overlapping images perceived by their left and right eyes. While cuttlefish have been known to possess binocular vision, this is the first study to reveal that they use their eyes in tandem (like vertebrates) to estimate the distance of prey before clutching it with the suckers of their tentacles and subduing it with toxins. However, the cuttlefish did not always appear to rely on coordination between their eyes--they moved their left and right eyes independently of one another, similar to chameleons, earlier in the hunt right up until the moment they chose to strike. Despite their impressive cognitive abilities, cephalopod brains are structured entirely differently from those of humans. However, their camera-like eyes are strikingly similar to those of vertebrates, leading scientists to wonder how cephalopod brains implement visual processes. To investigate whether cuttlefish use stereopsis to perceive depth, R.C. Feord et al. outfitted 11 adult cuttlefish from southern England with 3D glasses and showed them two overlapping images of a shrimp silhouette against a random pattern of bright and dark dots. The shrimp was hidden by the dots when the images were viewed individually, but when the wearer's eyes viewed them together they formed an illusion of a shrimp walking across a screen. Differently from both vertebrates and praying mantises, the cuttlefish could perceive depth through stereopsis regardless of whether the image was lighter or darker than the background.
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Journal
Science Advances