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.

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.

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What Really Happens When Food Goes Down the 'Wrong Pipe'?

The dreaded 'wrong pipe' calamity can strike at any time.
The dreaded 'wrong pipe' calamity can strike at any time.
Photo by Adrienn from Pexels

Your average person isn’t expected to be well-versed in the linguistics of human anatomy, which is how we wind up with guns for biceps and noggins for heads. So when swallowing something is followed by throat irritation or coughing, the fleeting bit of discomfort is often described as food “going down the wrong pipe.” But what’s actually happening?

When food is consumed, HuffPost reports, more than 30 muscles activate to facilitate chewing and swallowing. When the food is ready to leave your tongue and head down to your stomach, it’s poised near the ends of two "pipes," the esophagus and the trachea. You want the food to take the esophageal route, which leads to the stomach. Your body knows this, which is why the voice box and epiglottis shift to close off the trachea, the “wrong pipe” of ingestion.

Since we don’t typically hold our breath when we eat, food can occasionally take a wrong turn into the trachea, an unpleasant scenario known as aspiration, which triggers an adrenaline response and provokes coughing and discomfort. Dislodging the food usually eases the sensation, but if it’s enough to become stuck, you have an obstructed airway and can now be officially said to be choking.

The “wrong pipe” can also be a result of eating while tired or otherwise distracted or the result of a mechanical problem owing to illness or injury.

You might also notice that this happens more often with liquids. A sip of water may provoke a coughing attack. That’s because liquids move much more quickly, giving the body less time to react.

In extreme cases, food or liquids headed in the “wrong” direction can wind up in the lungs and cause pneumonia. Fortunately, that’s uncommon, and coughing tends to get the food moving back into the esophagus.

The best way to minimize the chances of getting food stuck is to avoid talking with your mouth full—yes, your parents were right—and thoroughly chew sensible portions.

If you experience repeated bouts of aspiration, it’s possible an underlying swallowing disorder or neurological problem is to blame. An X-ray or other tests can help diagnose the issue.

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