Y: Hey Don, an international team of neuroscientists has discovered how cuttlefish see in three dimensions.
D: But, Yaël, why study vision in a fish?
Y: Well, a cuttlefish isn’t really a fish. The animals are closely related to octopuses and squids and part of a group called cephalopods. Neuroscientists are interested in cephalopods because they evolved a complex brain along a different evolutionary path from the one that led to complex brains in more familiar animals with backbones, like fishes and humans. By studying a brain very different from ours, they hope to gain new insights about how all brains work.
D: I see. But you can ask a person whether they can see in three dimensions, but you can’t ask a cuttlefish. So, how can neuroscientists know?
Y: Cuttlefish capture smaller animals, like shrimp, as food. They do this by striking with their tentacles, which are covered with gripping suckers. To properly target their strike, they need to precisely judge the distance to their prey.
D: Now I get it. The scientists think the cuttlefish compares information from the different vantage points of its two eyes to judge depth, like we do. They could test this hypothesis by altering those binocular cues.Y: That’s it exactly. The researchers put special glasses on cuttlefish, like the ones people wear to watch 3D movies. They showed cuttlefish 3D movies of shrimp prey. By changing the binocular cues in the movie so that the cuttlefish’s tentacles struck too short or too far, they found that cuttlefish rely on these cues to target their strikes accurately. They hope the discovery will help tell us about how vision works in the brain.