(Intro)

Olivia: Plenty of people think of dogs as their best friends, and the fact that we live with them so closely means that we get to know them pretty well, but sometimes, our furry friends can act in ways that are surprising, beguiling, or downright mysterious, and over the years, we here at SciShow have answered a lot of questions about them.  Like, a lot.  It turns out we all have a lot of questions about dogs.  One of the first ones that springs to mind is 'Are they really colorblind or is that just a misconception?'  Turns out, dogs can see color, just not in the way we do.  Here's Michael with more.

Michael: Maybe you've heard that dogs can only see in black and white. It's one of those fun factoids that people like to toss around sometimes. But this, like so many things we talk about on Quick Questions, is a misconception. And the misconception stems from the fact that dogs are, from a human perspective, colorblind. But that doesn't mean they can't see color. 

We perceive color through a series of preceptors in the retinas of our eyes, called cones. And humans have three kinds, each of which is activated by a specific wavelength of light, corresponding to a certain set of colors. 

Most humans have cones that can detect blue, green, and red wavelengths of light, but dogs, kind of light humans who are colorblind, only have two kinds of cones that work.

For dogs, the two colors they can register are blue and yellow. So dogs can't see the color red, but they can see, and distinguish between, various shades of yellow, blue, gray, and something that probably comes through as a dirty-greenish-brown. 


So while we see this, your dog sees something more like this. It's not exactly technicolor, but it's a lot more information that just black and white. And, setting the record straight about dog's partial color vision is teaching us a lot about how pups experience the world. Recent experiments have found that dogs who are trained to find dark yellow objects could still find them, even if they were replaced with very dark yellow ones. And they didn't mistake dark blue objects for the dark yellow ones either, suggesting that dogs can clearly distinguish between many different shades and colors and don't just see in gray-scale.
So the next time you ask your dog to fetch your blue slippers, and he comes back with a pair of bananas, he's not colorblind, he's just messing with you.

Olivia: If your dog is smart enough to pull a prank like that, you might want to recommend them for doggy Mensa, or you might want to enlist them to test that old adage that old dogs can't learn new tricks.  It's possible we believe that because older dogs don't learn as readily as puppies, but research shows that teaching them new tricks could be a really nice thing to do for your senior pups.  Here's what the science says.

They say that you can’t teach an old dog new tricks but that saying might not be as trustworthy as you’d think.

Past puppyhood, dogs aren’t actually set in their ways. In fact, research shows that not only can old dogs learn new tricks, but teaching them could be a really good way of improving their quality of life. A few studies have investigated this specifically.

For example, a group of European researchers trained 265 dogs across multiple studies as recently as 2017 to push their noses against a touchscreen. It showed them pictures like flowers, cups, and other things. And when the canines picked the right picture, they were given a treat.

It took the animals a while to really get the hang of the game. But eventually, even the oldest doggy participants caught on, and they could consistently pick the correct picture to get a treat. While all dogs could learn to pick the right image, the researchers did notice that dogs over the age of 13 were much slower at learning than the younger ones.

And that’s because dogs, like humans, take longer to learn things as they get older. Dogs’ cognitive development parallels ours in some ways. Just like kids seem to be faster at picking up new languages than adults, puppies seem to be generally quicker on the uptake than older dogs.

A 2014 study that tested 145 border collies on skills like memory and attention found that dogs’ faculties start to decline as they get older maybe in a similar way that happens in humans. They also found that older dogs were just generally less interested in new stimuli. While puppies are curious about anything and everything, older dogs tend to lose interest in things more quickly, or tune them out entirely.

So in order for older dogs to learn new things, you have to try a bit harder to capture their attention. But even though it takes them a bit longer to learn new tricks, that doesn’t mean it’s any less important. The researchers think that just like older humans can derive satisfaction from brain puzzles like crosswords, a bit of mental stimulation might be great for keeping older dogs healthy and happy.

A 12-year-old dog might not have as much energy to play fetch as she did when she was a puppy, but she can still benefit from playing games. And computer games like the ones used in these studies require less energy, so they might just fit the bill. The researchers even suggested their experimental setup could potentially be adapted to let dogs play computer games at home.

So not only can old dogs learn new tricks research suggests it’s a great idea to try and teach them. It may be a little tougher for them, but it seems to be worth the effort. 

But what if your dog is tuckered out from a long day of educational computer games and just wants to chill for a bit?  You know, kick back and watch some YouTube?  You might have noticed your canine companion reacting to things they see on a computer or TV screen, suggesting that they can watch TV, at least sort of.  It turns out they don't see exactly what we do when they're looking at a screen, because TV screens are designed for humans, but dogs actually process visual information a little differently.  Here's Hank with the details.  By the way, this clip has some brief flashing lights, so if you're sensitive to those, just skip ahead until you see me again.

Hank: Does your dog ever seem more excited for the next season of Game of Thrones than you are?

Or, like, weirdly into barking at nature documentaries? If so, like a lot of our Patreon supporters, you might have wondered whether your dog is really watching TV, or if you’re just reading too much into things.

Well, science is here to tell you they are probably watching it. But they aren’t seeing exactly the same thing you are. Some dogs just seem to love watching TV.

Watching habits can vary by breed—some, like hounds, are mostly motivated by smell,so they’re less likely to be interested in the scent-free images on a screen. Herding dogs, on the other hand, tend to get excited when they see movement. So they may be more readily drawn to video.

But regardless of breed, what dogs see on the screen is definitely not what we see. Dogs’ visual systems are much more sensitive to flickering, which helps them perceive movement more efficiently. So, if you were to start flashing a light on and off slowly, then ramp up the speed,you’d stop being able to distinguish the flashes when it’s flickering faster than55 times per second.

A beagle, on the other hand, can see pulses that flash up to around 80 times a second. The image on an old, standard TV screen refreshes about 60 times a second: fast enough that we can’t see the individual pictures, but too slow to fool our furry best friends. So to your pup, your favorite show might look less like video and more like dancing in a very fast strobe light, or thumbing through a flip-book.

And that’s not the only part that might underwhelm them. No matter what type of TV you have, what might look to you like a vibrant, colorful image could be pretty “meh” for your dog. That’s because a typical scene uses a lot of hues they can’t distinguish.

Instead of having three different color receptors in their eyes like us, dogs only have two,so they only see the world in shades of yellow and blue. But if you really want Fido or Spot to be able to enjoy TV with you, science has some tips. There’s nothing you can do about the colors, but you can get a new TV if you’ve been holding out.

On a lot of modern TVs, the image on the screen changes more than 60 times per second. You can also choose shows that your furry best friend will find more engaging. Dogs can be drawn into watching videos by noises they already find intriguing, like barking or toys squeaking.

And unsurprisingly, they seem to like watching other dogs. Which is why we are going to have new SciShow, hosted only by dogs, four dogs, just dogs…That’s it. You’ll want to go for live action, not cartoons—so Lassie, not Clifford.

Dogs are intelligent enough to recognize photos and videos of dogs and other animals, which might be why they don’t respond well to animation— probably don’t look enough like the real thing. But maybe, we have anecdotal report from inside of the studio that it does works at least one dog. If you really want to go all out, there are even satellite TV channels with programming designed for dogs.

The brightness, colors, sounds, and camera angles are specifically chosen to appeal just to them.... What? But if your dog just isn’t interested in TV, don’t sweat it.

Researchers haven’t actually looked to see how screen time affects dogs, so we don’tknow if it has consequences long-term. And you might think your dog is already enough of a couch potato. And in any case they probably be just as happy, maybe happier, if you go on a walk, and that’s good for you too.

Olivia: We've all probably heard that if we love our dogs, we shouldn't give them chocolate, even if they see us enjoying it and seem to promise that they would love it, too.  Please, just a little taste?  Once again, this comes down to a key difference between humans and dogs, this time in how our digestive systems process the foods we've adapted to eat.  Here are the details.

If you have a dog you've probably heard that chocolate will make your pet sick, and that also applies to other pets like cats, rats, and mice. but that just doesn't seem fair.

Why do we get to go to town on a giant bar of dark chocolate but Fido shouldn't even have one bite? It all has to do with a molecule called theobromine which is made up of carbon, hydrogen, nitrogen and oxygen atoms.

And along with its partner caffeine, is one of the many reasons humans have loved chocolate for thousands of years. Both molecules are dangerous for dogs but chocolate contains a lot more theobromine than it does caffeine so it's the molecule to watch out for. Like caffeine, theobromine is a type of alkaloid, which is a huge class of molecules that generally contain rings with at least one nitrogen atom in them, and alkaloids often have physiological effects on humans and other animals.

Also like caffeine, theobromine makes our heart pump faster, our blood vessels dilate, and some of our muscles get more energy, which sounds great! But, too much of it can make our hearts pump too quickly and our muscles contract uncontrollably, eventually leading to nausea, convulsions, heart attack, and even death. Luckily for our taste buds, we humans process theobromine pretty quickly, so that's not something you have to worry about.

It rarely sticks around long enough to cause any harm. But, our pets aren't so lucky. They process theobromine a lot more slowly, so it can easily build up and cause those dangerous effects.

It's hard to know exactly why we evolved to be better at digesting theobromine, but it might be because alkaloids mostly come from plants, and our ancestors ate a lot more plants than early cats or dogs did. Whatever the reason, the same amount of theobromine stays in pets' bodies much longer, giving it more time to pile up and cause harm. On top of that, most pets are a lot lighter than humans, so it really doesn't take much chocolate to make them sick.

Cats don't often get poisoned from chocolate because they can't taste sweet things, so they're generally not too interested in it, But, dogs sure are. Your average adult human would need to eat about 8 kilograms of dark chocolate to get a lethal dose of theobromine. But, a medium-sized dog would only need to eat about one kilogram, and a house cat would only need a tenth of a kilogram.

Sweeter chocolates have less theobromine, so the lethal dose is higher; about 5 kilograms of milk chocolate for dogs and about a third of a kilogram for cats, but they'd be sick long before eating that much. Meanwhile, you and I will have to eat about half of our body weight in milk chocolate for a lethal dose, which might sound wonderful, but I don't want to see any of you writing "challenge accepted" in the comments, because you'd be very sick way before finishing that much chocolate. Among other things, I'm trying very hard not to picture what that would do to your digestive system But the next time to indulge in a chocolate bar, or three, just keep it to yourself, no matter how long your dog gives you those adorable puppy eyes.

But how in tune with our emotions are they really?  Do they know we're sorry we can't give them chocolate?  Or what about the old bit of folk knowledge that dogs can smell fear?  There's actually a bit of research to back that one up.  It's possible that dogs really can sense certain emotional states thanks to the chemistry of our sweat and their incredible sense of smell, at least maybe.  Here's Hank to tell us about it.

Hank: If it hasn't been said to you, you've probably heard it on TV or in a movie. Stay calm around strange dogs because they can smell fear and they might attack, but until recently, scientists hadn't looked to see if that was true.

Now we know that they can smell fear, but when they do, they don't get aggressive. They actually get scared, too. Dogs have amazing noses.

Their sense of smell is 10 to 100 thousand times better than ours, which is why they can help us detect traces of chemicals from bombs, drugs and even people buried under the snow. That's thanks to the sheer number of olfactory receptors they have. Up to three hundred million, compared to our measly six million, and to the fact that, relative to their size, the part of their brain that analyzes smells is about 40 times the size of ours.

But even so, dogs don't rely entirely on their sniffers. When they want to communicate with each other or with us, they usually can use body language and vocalizations as well. When we tell them they're such a good doggo, they process the tone of our voice and the words that we're speaking in different brain areas, just like we do when other humans talk.

Which means they do understand what we're saying to some extent, and we know that dogs are good at picking up on physical signals. In fact, studies have shown that they can differentiate between our emotions based off of our faces and body language. So for a while most scientists and dog trainers figured that dogs don't need to sniff out our feelings.

They can see it in our posture and hear it in our voice. It wasn't until recently that researchers looked directly into whether dogs can smell fear. When we're afraid, the sweat we produce contains different chemicals than when we're happy or sad, because the composition of our blood changes in response to hormonal signals.

So scientists can stick swabs in our armpits while inducing different emotions, and then see how dogs react to those odors. And they did this in a 2016 study published in Behavioural Brain Research, and then found that dogs' heart rates increased when they sniff sweat from people who watched a scary video, suggesting that they can smell fear, but the animals had the same reaction to sweat from people who worked out, so it wasn't clear if they were just sensing physical arousal. Then a study in Animal Cognition in 2017 did a similar experiment.

They had dogs sniff pads with sweat from people who watched scary or happy videos or unused pads, but this time the researchers watched the dogs' behavior afterwards and looked at heart rate. The dogs that smelled the happy sweat were friendlier to strangers. Their heart rates were generally higher than the control's, but lower than the dogs that had sniffed the fearful sweat.

Meanwhile, the dogs that smelled fear seemed stressed out, seeking more reassurance from their owners, and acting more wary of new people. And like the previous study, their heart rates went up. So the researchers concluded that the dogs were detecting emotions, and reacting by feeling a similar way.

Sniffing joy put them in a better mood, and the smell of fear didn't make them more aggressive—it scared them. So it seems like dogs can potentially smell fear and know how you're feeling, but rest assured the feeling will probably be mutual.

Olivia: But smell isn't the primary way dogs communicate with us.  Tails wag, ears perk up, and if you're lucky, you'll get one of those doggy smiles, and we have our own ways of communicating with them, too.  We make very specific changes in our voices when we speak to dogs, as you know if you've ever veered into the 'Who's a good boy?' territory.  The really interesting thing is that this isn't just about us putting on a silly voice when we see a cute puppy.  It actually seems to affect how dogs interact with us.  Here's Michael to tell us about the research.

Michael: It’s hard to resist. You see an adorable puppy in the park or outside a cafe and all of a sudden, your voice jumps up about two octaves and you’re talking total gooey nonsense.

Who’s a good boy? But there’s actually a good reason for this puppy talk and it has a lot to do with the bond between person and pooch. So-called dog-directed speech is actually very similar to the way we talk to babies, which is called infant-directed speech.

It’s higher pitched, slower, and kind of sing-songy compared to our usual conversational tones. Because both dogs and infants are non-verbal, researchers believe we exaggerate the other parts of speech, like melody or pitch, to keep their attention. And it seems to work, at least in younger dogs.

In an experiment published in 2017, a loudspeaker played pre-recorded puppy talk for 10 dogs and 10 puppies. The puppies approached the speaker more quickly and sat by it for longer when the speaker played cutesy puppy talk than they did for regular adult speech. But it may not be just the tone.

Dogs may pay attention to the content of our speech as well. Which, sure, dogs can’t talk, but dog owners know better than to casually use words like “treat” or “walk,” unless you’re ready for the consequences, in the form of puppy excitement. And in a 2018 study, researchers tested dogs’ responses to our content versus our tone, by creating a mishmash of dog-directed and human-directed speech.

When they played typical doggy talk in a dog-directed voice “Come on! Let’s go for a walk!” The dogs preferred it to typical adult-directed speech. Experimenters also read human scripts about boring human stuff like going to the gym, but it was spoken in a cute doggy voice.

They also recorded the opposite: cutesy “Who’s a good boy” phrases in a normal adult voice. When they played the recordings to adult dogs, the dogs had no preference for doggy talk when the cutesy style of speaking was used to talk about boring, non-dog topics. Apparently, the doggy words mattered too when it came to getting their attention.

And dog-directed speech might have another function too: improving the bond between human and animal. Dogs and wolves yowl in a high pitch when greeting each other and when asking for food or care from their mother. And some scientists hypothesize that we humans might have unintentionally hijacked this form of communication.

During our domestication of dogs many thousands of years ago, we might have selected for ones who were more tuned in and reacted positively to this way of talking, by wagging their tail or yapping back for example. Alternatively, we might just train our puppies from birth to respond to our cute puppy talk. Either way, in that 2017 study, the authors suggested that the adult dogs may already be bonded to their owners, and not care what the experimenters were saying, and that’s why they didn’t care about dog-directed speech like puppies did.

And the research overall suggests that we humans don’t just talk to our dogs this way to be all gooshy. The dogs actually respond to it, and it strengthens our bonds. So don’t feel weird about veering into goofy dog-directed speech every time you see a corgi.  You're just furthering thousands of years of companionship.

Olivia: Thanks for watching this SciShow compilation, which was brought to you with the help of our Patrons on Patreon.  Thanks, as always, for your support and your great questions.  If you're interested in joining our community of Patrons, check out Patreon.com/SciShow.  

(Endscreen)