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Today on the SciShow Talk Show, our Technical Director Nick Jenkins stumps Hank about how many frames per second the human eye can see, and Jessi from Animal Wonders shares Hara the Harris's hawk.

Learn more about Hara!
Want more animals? Check out Animal Wonders Inc. at or on YouTube at

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[intro music]

Hank: Hello, and welcome to another edition of the SciShow Talk Show. Today we have in the studio with me, my friend and technical director, Nicholas Jenkins.

Nick: Hello.

Hank: So, today on the SciShow Talk Show Nick is going to attempt to stump me, and then he's going to tell me something interesting, and then we're going to meet an animal. That's what we do here on the talk show. So, we're gonna start with the stumping. (0:33)

Nick: Yes.

Hank: What are you gonna do to me?

Nick: Okay, well, so bear with me here. Do you know what that is?

Hank: That's a piece of film.

Nick: Yes, this is one frame of 35 millimeter film. So that's one frame. How many of these are there- When you go to see a film, how many are there per second.

Hank: 23.97?

Nick: Not really. There's 24.

Hank: 24! Why does it say 23.97 when I'm exporting in Final Cut?

Nick: That's because you're shooting digitally, and there's a whole different thing that we won't get into there.

Hank: There's a whole different thing. Okay!

Nick: But-

Hank: 24

Nick: There's 24 of those. So here we have one second of 35 millimeter film. This is actually from a commercial that would play before the movies. This one was for a soda of some sort.

Hank: Yes, it looks like a Coca-cola. Which is what's in my mug right now.

Nick: And this is one minute.

Hank: Where did you get these?

Nick: I'm a filmmaker.


Hank: It comes with the diploma.

Nick: Apparently. So there's that. But all of this has a point and the point is, I wanna talk a little bit about our brains and how our brains process images.

When we watching these things, when we watch films or even video, we're not watching movement. We're watching the illusion of movement, right? Because we're watching still images back to back. We watch 24 frames of them or 30 frames or 60 frames, some places overseas for sports, are actually trying to do like 300 frames as a 'normal' thing, which is a lot of information. So the question becomes, if that works for film how does that translate to our eyes? The Stump Hank part is, what does the human eye see at, in terms of frame rate.

Hank: How many frames per second does my eye see?

Nick: Yes. Or, well, more technically your brain.

Hank: Ah, because I guess the brain would be equivalent to an analog. Or the eye would be the analog and then there's like a digital conversion basically.

Nick: Pretty much.

Hank: At the back of the retina.

I'm thinking of propellers and how you start to see the propeller go, and then it becomes a blur, and then it starts moving backward. I feel like from that information you could extrapolate an actual frame rate, but I don't have any idea what it would be. I know that I'm comfortable at 24 frames per second, but I know that you can detect the difference between 24 and 60.

Nick: Right.

Hank: So between those two somewhere, is my guess.

Nick: Okay, this is actually a lot more complicated. You might even call it kind of a trick question in some respects. Comparing what a camera does or what a projector does to what our eyes and brains do, it seems like a good idea. It seems like something that would be simple to compare, but actually they work on, like, almost completely different principles of how they function.

Hank: Yeah, so it's like that episode we did on brains versus computers and it was like, "The brain versus the"

Nick: Exactly. The ways our eyes work is not in a term of click, click, click, click, click, image, image, image, image, image. It's a constant stream of information coming into us, so it's very very fast that we actually get the information. Now where the slow down comes is when your brain has to make meaning out of those images. But that all happens in a steady stream. It's not really like image, image, image, image. It's always getting information in different ways, different light, you know all kinds of stuff, different parameters. You know, you have the straight on view and then you have the peripheral vision. So the question of how many frames per second do we see, and this is a very common question on the internet. A lot people ask this question and you get a lot of different answers and most the of time you see people sort of, "well let's change the question because that doesn't quite work." And the question you want to change it to is actually, "How many frames per second does it take to achieve movement in what we're seeing?" We sort of arbitrarily came up with 24 frames, way back, but it turns out, in order to see movement in a film image, in photographic images, it's about 16 frames per second. That's where we stop.

Hank: Right, that makes sense to me. I mean, back in the day, on the internet there would be 15 frame per second videos.

Nick: Really?

Hank: People used to do that to save information.

Nick: To save like bandwidth and stuff?

Hank: Yeah, because there just wasn't enough bandwidth and so you'd have like 120p videos at 15 frames per second. That was like back, back, back, back in the day if you remember those-

Nick: just making GIFs

Hank: -CompuServe. Well, it was when GIFs were hard to download. And sometimes people do make GIFs at a lower frame rate so they can get them down below one megabyte to upload them to Tumblr. But this is making me think of a thing called the second hand illusion. I don't know if you've heard of that.

Nick: I haven't.

Hank: But, so when you move your eyes, there's a space, you don't see the blur like if you moved a camera you'd see this blur across the screen, but when you move your eyes you don't see that blur.  There is information taken out by your brain. Your brain is like, "That information is not useful or interesting."

Nick: Extraneous. Get rid of it.

Hank: And so what it does is it keeps your- Your brain only sees that thing and it stays on there and then transports what you end up on in your consciousness into like, ya know, the past. And so if you look at a second hand, and you catch it at the right time, it will actually stay where it, like, it'll stay for longer than a second before it clicks over and that's the only way that you can like detect this in your brain. And it's crazy that our brains are just doing these things without our permission and we have no idea.

Nick: [laughter] Yeah, but it's interesting because it's not that you didn't see it, your brain just decided it didn't need the information.

Hank: Right, to filter it out. I mean, it came to the retina but then for whatever- at whatever step down the path- And so probably what I should have answered when you asked this question was- I probably could have, if I thought about it long enough, said, "Not relevant."

Nick: Exactly!

Hank: That's what I should have said.

Nick: That's what I had for my Stump Hank.

Hank: And I was pretty much stumped. I should have done better on that one. But I appreciate it and it was very interesting and I love that you have props.

Nick: I always have props

Hank: So now, we're going to have a better prop which is something. I don't even know what it is yet. It's going to come-

Nick: I think we're going to see something big that flies.

Hank: Oh, he knew!

 Special Guest

Hank: We have a very special guest here today. Jessi tell us about this animal.

Jessi: This is Hara, the Harris's Hawk. She comes from the desert. She is not going to be found in the Northwest, up here in Montana. Um, she's going to be found in the deserts of the, Southern United States, through Mexico, through Central America, all the way down to, Argentina, basically. Through South America. Any desert you'll find the Harris's Hawk.

Hank: This is why I have not seen this hawk before.

Jessi: Yeah, yeah.

Hank: Yeah, ever. This is not a familiar species.

Jessi: Woah, that little thing! She's saying is there some place I can fly off to? 

Hank: Yeah

Jessi: She's looking around.

Hank: No, that's just the ceiling.

Jessi: Not much, huh. [laughter] So Hara here, um, let's talk about some of the interesting things these guys do. They're pretty neat hawks. They're a lot different than other hawks, that you might find, in the Americas. They, you know, they look really neat, but it's not what they look like that makes them neat, it's what they do. 

Hank: Their behavior.

Jessi: Yep, that's what makes them neat.

Hank: Yeah, but the tail feathers seem larger to me.

Nick: Yeah.

Hank: But that might be because I don't have very experience of looking at hawks close up.

Jessi: Their tail feathers, maybe it's that white that's kinda highlighting them. She's spreading her tail just a little bit. Um, she's just using it for balance, you can see how she can move her tail up and down to help her balance as I move my glove here.

Nick: Awwww, that's cool.

Jessi: Yeah, so let me tell you about their behavior, about these guys. So they live in the desert. And there is not a lot to eat in the desert, and the food that can find, lizards, and rabbits and other tiny little rodents and stuff like that. They're pretty smart. They know the game. They're not going to be out in the sunshine during the day, cruising around in the desert, they are just going to get spotted real easy. So they're all going to try and hide. 

So these guys are hanging out. Now the first thing that makes them unusual, is they hang out in groups. Most hawks it's either single, or it's just their mate, that they hang out with. These guys will hang up in like groups of five. A lot of times it's just one female and four males. And, there is like five of them cruising around in the sky looking for food, they can't find anything. So she'll send down a couple of her friends down to the ground. What they'll do is, they'll land on the ground, then they will storm in to a bush, as fast as they can.

Hank: Like pack hunters.

Jessi: And try and flush out anything that's hiding in that bush. So say some mice and a rabbit flush out of that bush. Um, so then Hara is up in the sky, and she will come down and she'll grab a hold of whatever prey she can. Now if it's a mouse, she'll grab it. And she's not going to grab it with her mouth or her beak here. The most dangerous part of a raptor is those talons there.
Amazing feet. Wanna show off those feet. (bird flaps) There you go, there you go.

Hank: ooofff

Jessi: Amazing talons. You're looking at them to?

Nick: She knows what's up.

Jessi: yeah. So she will grab them with those feet and she is going to squeeze them as hard as she can. Now she can actually eat a full grown mouse in one bite. She can just swallow it on down. 

Hank: So, so her co-conspirators aren't going to get a piece.

Jessi: What she's going to do, is she will try and hide it from them. She'll hold on to it until it stops breathing. And she is actually going to do this neat behavior, where she mantles over it. She'll take her wings and kinda hide the food as she finishes eating it.

But if it's a rabbit, say that's the only thing they flush out the bush, she can't take down a rabbit herself, a rabbit would actually weigh more than she does, even though it might be smaller.
So she'll dive down and she'll grab on to the rabbit, and one of her friends will come over and grab onto it to. Maybe even a third friend will grab on to it too. And they will all take it down. And then they'll communally share that meal. 

Hank and Nick: wow.

Jessi: Which is very unusual for raptors.

Nick: Very unusual.

Hank: That's like pack birds.

Jessi: Yeah.

Hank: I never even heard of that.

Nick: I haven't either.

Jessi: They're very very smart. The other things that these guys do, that's kinda silly is...

Hank: oops.

Jessi: (laughs) is they, er, do this thing with their perching. So in the desert there is not a lot of places to perch, there's not a lot of trees. So they're gonna perch on a cactus. Sometimes there is only one little place for them to perch on top. So one will perch on top, and the other one will come and perch on that one's back. And another will perch on that one, you'll have this stack of five Harris's hawks.

Hank: That's crazy!

Jessi: On top of a cactus. (10:52)

Hank: This is really making me feel like if - if, uh - this bird were maybe twice as large as it is that I should really be worried for my-

Jessi: (laughs)

Nick: Yeah.

Jessi: 'Cause they're so smart?

Hank: Yeah, well if there's like five of them, they'd be like "mmm, maybe I could take down a human".

Jessi: Yeah, oh yeah.

Hank: Yeah.

Jessi: Yeah, hmmm.

Nick: They're just this close to having a union.

Hank: Yeah.

Jessi: (laughs)

Hank: Yeah, I, I had never heard of birds hunting in packs

Jessi: It's pretty neat.

Hank: 'Cause that's a, that's a whole 'nother, new level of social behavior

Jessi: Yeah

Hank: -where you're, y'know, you've got hierarchies and,

Jessi: Mhmm. And actually the one on the bottom has the, is the lowest on the hierarchy, the one on the top is the best, has got the best perch.

Hank: That, uh

Jessi: Best seat in the house!

Hank: That is, uh, exactly what you would think.

Jessi: Yeah.

Hank: It's, uh, it's metaphorical, and, uh

Nick: (laughs)

Jessi: (laughs)

Hank: and

Jessi: Yeah.

Hank: Hara, thank you very much for coming and visiting with us on this episode of SciShow Talk Show, and you Jessi as well.

Jessi: Thank you.

Hank: This was very cool.

Nick: Yeah, this was amazing.

Hank: Thank you for joining us here on the SciShow Talk Show and thank you to Nick for being here as well. We'll see you next time.

[end music]