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Pi, like 3.141592653589. Each of those 13 digits has a month devoted to it in this awesome calendar.

You can find it for a limited time at ComplexlyCalendars.com. [♪ INTRO] While you will never catch a fish with a calculator in its fin or at a chalkboard writing complex equations, that doesn’t mean they can’t perform some basic math functions. Yes, math. Researchers have found that several species of fish can estimate quantities and maybe even count… to four.

And now, scientists are especially interested in using one fish species, the zebrafish, to better understand how brains are capable of estimating in the first place. Because if they can figure out how zebrafish brains work when it comes to basic math, it could help diagnose and address learning disabilities in humans in the future. Even if you aren’t doing calculus on the regular, basic math comes in handy.

And you don’t have to be human to have math skills. Being able to estimate quantities is super useful when other animals are figuring out whether it's better to face down a group of predators or run away. Like, fish often school together in large groups, and the bigger the group, the less likely every individual is to be eaten.

So, if they have to choose between different-sized schools, it’s in their best interest to be able to tell which is bigger. And scientists have seen this happen. They’ve tested mosquitofish and guppies, and found that they can tell when one group of fish is twice as large as the other.

When presented with two groups of fish, where one was at least twice as big as the other, they reliably picked the bigger squad. When the large groups were closer in size, these fish weren’t as accurate. But in other experiments, researchers have had fish choose between two small groups.

And there, things got interesting. Researchers have presented several species, including angelfish, guppies, and mosquitofish, with a choice between groups of other fish buddies that varied by one. So, an angelfish might be asked to choose between a group of two or three friends, or three or four, and so on.

Then, they watched to see which group the fish would choose. An angelfish could reliably choose the larger group if the number of fish in the bigger group was three or less. They could distinguish between two fish and three, or two fish and one.

And mosquitofish could discriminate between three and four fish, but that was their limit. According to the researchers, because these groups of fish were so small, the results suggest that the fish might not just be estimating group size: they may be doing some sort of counting to compare them. And this was true even when researchers removed other variables, like sounds, smells, or other visual cues that would tell the fish, “Hey, we’re the bigger group over here.” Researchers have even gone so far as to teach mosquitofish to discriminate between groups of two or three, using shapes.

They trained fish to recognize that picking a door with the number of shapes they’d been trained on, either two or three, would always lead to finding their social group behind it. Then, they tested the fish to see how they were differentiating between the group of two symbols and the group of three. They slowly removed all the things the fish could have been using to tell them apart without counting, like the overall area of the shapes or their size.

In the end, the fish could reliably pick the number of shapes they’d been trained to recognize, even when all the other variables were equal! The researchers concluded this indicated they probably had some basic ability to count, rather than just estimate which door had more shapes. Which is no small feat!

This isn’t even a universal ability among humans. Most likely, though, fish aren’t swimming around counting every individual in a school before they join up. Fish usually school in groups larger than four, so they probably estimate more.

And you might do the same thing when quickly picking between groups. Like, in the cafeteria line, you’re not going to count every french fry in the pile to figure out which pile is bigger. You’d rely on your estimating skills.

But for fish, estimating is even more important for survival than getting the best basket of fries. Picking a big school helps them avoid predators, and estimating can also help them make snap decisions about which group of prey is big enough to be worth the energy to pursue. All that said, scientists don't currently know a lot about what's happening in a fish’s brain to help them estimate.

But they suspect that whatever it is, it’s also happening in human brains. And that’s partly because of what they’ve seen in zebrafish. These little striped fish are great model organisms, meaning they’re often used by researchers because they have a lot in common with other vertebrates.

For example, zebrafish have all the same major neurotransmitters, hormones, and receptors as mammals, including humans. And they have complex behaviors that can mimic mammal behaviors, including having math skills. Also, as a bonus, zebrafish babies are transparent, so researchers can literally peer into their brains and see how their neurons work.

And it turns out, these fish aren’t so different from us. Studies found these fish use similar parts of their brains as mammals and birds to estimate quantities. Researchers even suspect that the human ability to estimate may have evolved in an ancient ancestor, dating back long before our ancestors left the aquatic realm.

So, understanding what’s happening inside fish brains could help researchers get a better idea of what’s going on in our brains. This could even help them understand and treat learning disabilities that can cause people to struggle with basic math functions. So while fish in that nearby pond aren’t solving complex equations, they are using basic math and estimating skills to help them survive.

And by digging into the way fish brains work, researchers may be able to better understand the human brain along the way. Because really, basic math can be life-changing, even if you’re just a fish! Fish have joined the club of animals that recognize just how much numbers can tell us.

Now, we don’t have evidence as to whether or not they know about numbers like pi, but we humans sure are better off with pi in our lives. And to keep it a present part of your daily life, we’ve created a pi calendar for sale now! Yes, pi day is a holiday highlighted in this calendar on March 14th.

And that day is also the International day of mathematics! And if you want to be notified when these and other equally important holidays are coming up, you can get your very own pi calendar at ComplexlyCalendars.com or through the link down below in the description. Some of the people who worked on this video also worked very hard to make this calendar.

So if you like SciShow videos, you’ll probably like this as well. And thank you for your support! [♪ OUTRO]