Scientists Put 3D Glasses on Cuttlefish and Find Out They Use Human-Like Depth Perception to Hunt Prey

Trevor Wardill
Trevor Wardill

Researchers at the University of Minnesota recently constructed a miniature underwater movie theater, outfitted a group of cuttlefish with 3D glasses, and proceeded to show them short movies of shrimp—all to see if humans and cuttlefish have more in common than we previously thought.

Cuttlefish, squid-like cephalopods with an internal shell, ensnare prey with one swift snatch of their tentacles. If they under- or over-estimate their distance from whatever unsuspecting marine animal they’re eyeing, however, they’ll fail to grasp their prey and give away their position, too.

To find out how cuttlefish estimate distance so accurately, Trevor Wardill, assistant professor in the University of Minnesota’s Department of Ecology, Evolution, and Behavior, and his team devised an innovative study, published in the journal Science Advances. After placing 3D glasses over a cuttlefish’s eyes, they set it in front of a screen that showed offset images of two different-colored shrimp on a leisurely walk.

cuttlefish in 3d glasses
Trevor Wardill

If you’ve ever briefly taken off your 3D glasses during a movie, you’ve seen the offset—or partially overlapped—images that filmmakers use to create the illusion of depth. The process by which we perceive depth is called stereopsis, where our brain receives different images from our left and right eyes and combines that information to help us understand when some objects are closer to us than others. When you’re watching a 3D movie, your brain is combining the offset images, as seen differently by your left and right eyes, to make you think that flat images have depth, and some are closer than others.

And, as demonstrated in the experiment, the same thing happens with cuttlefish. The researchers varied the positioning of the offset images so the cuttlefish would either perceive the shrimp to be in front of or behind the screen. When the cuttlefish then struck out at their would-be prey, their tentacles ended up grasping at empty water (if they thought the shrimp was in front of the screen) or colliding with the screen (if they thought the shrimp was behind it). In other words, stereopsis allowed them to interpret how far away the shrimp was, just like humans would have done.

"How the cuttlefish reacted to the disparities clearly establishes that cuttlefish use stereopsis when hunting," Wardill said in a statement. "When only one eye could see the shrimp, meaning stereopsis was not possible, the animals took longer to position themselves correctly. When both eyes could see the shrimp, meaning they utilized stereopsis, it allowed cuttlefish to make faster decisions when attacking. This can make all the difference in catching a meal."

But cuttlefish brains aren’t as similar to ours as their depth perception skills might imply.

“We know that cuttlefish brains aren’t segmented like humans. They do not seem to have a single part of the brain—like our occipital lobe—dedicated to processing vision,” Wardill’s colleague Paloma Gonzalez-Bellido said in the press release. “Our research shows there must be an area in their brain that compares the images from a cuttlefish’s left and right eye and computes their differences.”

Unlike squids, octopuses, and other cephalopods, cuttlefish can rotate their eyes to look directly forward, so the experiment isn’t suggesting that all cephalopods can use stereopsis. It is, however, suggesting that we may have underestimated invertebrates’ capacity for what we consider complex brain computations—and overestimated how unique humans actually are.

Wayfair’s Fourth of July Clearance Sale Takes Up to 60 Percent Off Grills and Outdoor Furniture

Wayfair/Weber
Wayfair/Weber

This Fourth of July, Wayfair is making sure you can turn your backyard into an oasis while keeping your bank account intact with a clearance sale that features savings of up to 60 percent on essentials like chairs, hammocks, games, and grills. Take a look at some of the highlights below.

Outdoor Furniture

Brisbane bench from Wayfair
Brisbane/Wayfair

- Jericho 9-Foot Market Umbrella $92 (Save 15 percent)
- Woodstock Patio Chairs (Set of Two) $310 (Save 54 percent)
- Brisbane Wooden Storage Bench $243 (Save 62 percent)
- Kordell Nine-Piece Rattan Sectional Seating Group with Cushions $1800 (Save 27 percent)
- Nelsonville 12-Piece Multiple Chairs Seating Group $1860 (Save 56 percent)
- Collingswood Three-Piece Seating Group with Cushions $410 (Save 33 percent)

Grills and Accessories

Dyna-Glo electric smoker.
Dyna-Glo/Wayfair

- Spirit® II E-310 Gas Grill $479 (Save 17 percent)
- Portable Three-Burner Propane Gas Grill $104 (Save 20 percent)
- Digital Bluetooth Electric Smoker $224 (Save 25 percent)
- Cuisinart Grilling Tool Set $38 (Save 5 percent)

Outdoor games

American flag cornhole game.
GoSports

- American Flag Cornhole Board $57 (Save 19 percent)
- Giant Four in a Row Game $30 (Save 6 percent)
- Giant Jenga Game $119 (Save 30 percent)

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Map Shows How Everyone Blamed Syphilis on Everyone Else

Portrait of Gerard de Lairesse by Rembrandt van Rijn. De Lairesse, a painter and art theorist, had congenital syphilis that deformed his face and eventually blinded him.
Portrait of Gerard de Lairesse by Rembrandt van Rijn. De Lairesse, a painter and art theorist, had congenital syphilis that deformed his face and eventually blinded him.
Gerard de Lairesse, Wikimedia Commons // Public Domain

The origins of syphilis may be one of the greatest (and grossest) health mysteries of our time. Some historians claim that Christopher Columbus and his sailors contracted the sexually transmitted disease in the New World and brought it back to Europe. Other experts believe that the disease, which is caused by the bacterium Treponema pallidum, existed in various forms around the globe but was simply misclassified as other conditions. (European writers, including Italian historian Niccolo Squillaci, first described syphilis in the late 15th century.) And in 2015, researchers announced that they had identified signs of congenital syphilis in 14th-century skeletons from St. Polten, Austria, adding new evidence to an ages-old debate.

One thing's for sure: As the map below illustrates, nobody wanted to take credit for originating the virulent condition. Created by Redditor masiakasaurus (and spotted by The A.V. Club), the map illustrates the various nicknames Europeans gave the disease before the name syphilis caught on. (Italian physician and poet Hieronymus Fracastorius coined the word in 1530 with his poem "Syphilis Sive Morbus Gallicus" ("Syphilis or the French Disease"). Not surprisingly, nearly every single moniker used for the disease places blame on another group for giving birth to what by then had become a continental scourge.

“Most physicians felt that this was a new disease, that it hadn’t been seen before in Europe, and that view tended to prevail for quite some time,” medical historian John Parascandola told The Atlantic in 2016. “There were certain tempting reasons for people to accept that—blame it on the others, blame it on the outsiders. Before that, the French were blaming it on the Italians, the Italians were blaming it on the French, et cetera.”

Masiakasaurus sourced the syphilis nicknames from nine scholarly books/journals, including The Early History of Syphilis: A Reappraisal,The rise and fall of sexually transmitted diseases in Sweden, and A Medical History of Persia and the Eastern Caliphate: From the Earliest Times Until the Year A.D. 1932. You can view the full list on Reddit—after giving silent thanks to Alexander Fleming for discovering penicillin, found to be an effective cure for syphilis in 1943.

[h/t The A.V. Club]