An international team of neuroscientists has discovered how cuttlefish see in three dimensions. First of all, 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 humans. By studying a brain very different from ours, they hope to gain new insights about how all brains work.

Of course, it's pretty easy to ask a person whether they can see in three dimensions, but you can't ask a cuttlefish. Neuroscientists had to think of another way to answer the question.

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.

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.

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 rely on these cues to target their strikes accurately. They hope the discovery will help tell us about how vision works in the brain.