[Music] how do they know what colors dogs can see there's this myth that won't go away that dogs only see in black and white but that's just not true there's a bunch of apps and filters now that claim to show dog color vision but where does our understanding of this K9 rainbow come from and do these filters really capture how dogs see the world before we get to dogs how do we know what colors humans can or can't see I'm sure you've seen these before right yeah do you have normal color vision I have I
think normal color vision I think that says 45 so what just happened there light from this image entered Cleo's eye where it hit cells in her retina called cones that in turn sent electrical signals to her brain which created her perception of color this rainbow is just how our brain translates different wavelengths of light from one small section of the electromagnetic spectrum Cleo like most people has three types of cone cells each one sensitive to a different part of the spectrum relatively short wavelengths of light medium wavelengths and long their sensitivity Peaks at specific points
but it drops off smoothly in both directions so when what we call orange light comes in and hits an S cone its wavelength lands outside this sensitivity curve but if it hits an M cone a signal is produced and with the El cone an even stronger signal these signals are combined and interpreted by the brain as orange when so-called green light comes in the cones send a different set of signals green green and so people with normal vision can make out the number 45 in this pattern but what if you were missing this m col
like about .5% of the population both orange and green light would stimulate the elone about the same amount and without the M cone the signals would be too similar the brain wouldn't be able to distinguish between them and the number 45 would disappear into the background for those who can't read numbers like todders there are versions of this test that just have the subject trace a loopy line but how do you design a vision test for a dog if I were trying to do this with Thor I would concoct a test that involves getting food
at the end if an only if he can demonstrate that he can see two different colors that's pretty much what Jay Knights did back in the late 1980s I said we have to solve this question once and for all I went home at lunchtime and got my dog a toy poodle appropriately named retina brought him into the laboratory 7 days a week for a year lab setup was a little chamber there were three discs illuminated from behind the dog was trained to Boop whatever disc looked different with her nose if she chose right she heard
a click and got a little treat if she chose wrong no treat and a buzzer sound once retina learned that Jay wanted her to identify the different Circle it was time for the real experiments one of the first experiments that we did we had three different white lights and then we added a little bit of the particular color at first we'd add a little bit and the dog can't see it but add more and the dog can pick it out and if it takes a very small amount any particular wavelength that means that they must
be very sensitive for each color they plotted out this sensitivity and we just marched across the whole entire rainbow this sensitivity curve strongly suggests that dogs have just two cones centered here and here and at this low point in the middle something interesting happened retina couldn't tell the difference between this color and white light there's some wavelength in the middle part of the spectrum that's kind of where the two cones out overlap the light equally stimulates the two cones when all three of our cones are equally stimulated humans see Shades of Gray and the same
would be true for dogs with their two cones for them this is the point of that equal stimulation another set of experiments mimicked those color blindness tests we talked about before and as you'd expect from someone with just two cones Rea struggled to tell the difference between oranges and greens Jay confirmed his results with two other dogs and published them in 1989 now my dog is much more famous in the realm of science that I am follow-up studies gathered similar data and if you put that together with what we know about human Vision you can
start to paint a picture of the rainbow that dogs see blue on one end Fading Into gray in the middle and then yellow on the other end it's probably not that different from what a human missing their M cone would see it makes me wonder how many times I have interacted with Thor in a way that kind of expected him to be able to see the full spectrum of color can I just put a filter on an image and be like oh this is what dog aene or are there complications to that oh I think
it's it's way more complicated than that but that's a good first pass is it anywhere near the subjective experience I think not I mean there's a lot more complications just in the retina to begin with in addition to cones mammals have Rod cells that help them pick up light and motion and dogs have way more of these kinds of cells than humans that makes them more sensitive to movement and helps them see in low light they also have a layer called the deum lucidum that reflects light back through the retina that's what makes dogs eyes
shine at night then there's a difference in the arrangement of cells in the retina we have lots of cells across all of the back of the eyeball but a especially dense group of cells in the center which enables us to see the thing that's right in front of us but some breeds of dogs are different they have a density of cells that sort of extends oh I just f um they have a density of cells uh that I love and that horizontal band of cells might make it easier for them to take in visual information
across a broader swath of the Horizon the position of their eyes often gives them a wider field of vision but less overlap which means weaker depth perception dogs are also mostly nearsighted distant things are fuzzier then additionally dog's visual experience of the world is going to be completely tied up in the OR Factory experience of the world and this is the aspect of dog Vision that I don't think we humans can ever fully understand so this is just an image of the olfactory ponal in the human on the left and the dog on the right
these are called Podunk these are olfactory Podunk yeah that's a great word wow the olfactory system in the human takes up approximately .3% of the brain dogs do have a a hugely larger olfactory system they are detecting things that we are completely unable to detect there's a bunch of studies that show dogs can smell cancer malaria covid-19 explosives diseased avocado trees whale poop on the ocean even the emotional state of their owners you know I do sometimes think when I put perfume on what my dog is thinking because it must be quite overwhelming for them
here's another way to look at the brain these are tractograms made with a special MRI technique and these lines trace the paths of white matter the fibers that speed signals between different regions of the brain you can virtually dissect these tractograms highlighting different roots roots for example here are the paths extending from Human old factory podal to other regions but here is the dog brain whoa there's information freeways running from the nose to other parts of the brain and these weren't found before just because no one really looked yeah pretty much can you guess what
this is circling it's going here yeah what is there do you know I have no idea what's here me it's a little counterintuitive because in both humans and dogs the place that we process vision is actually the back of our head this occipital lobe back here oh so what you're saying is dogs are processing uh smell like we are processing sight sort of well it's interesting because it's not unique to the dog that they might use a different sense to generate Vision I mean we know the bats are a classic examp they can navigate through
their auditory Pathways it's very possible that dogs can identify structures in the room from scent as well as from from Vision seeing and smelling are interwoven in an important way and that is something completely unlike what we have in our brain when I think about my sense of the world my mental map of where I am in space where other things are like how those things relate to each other and move like all of that is visual we literally use the word visualize like that's that's what I'm thinking um yeah but for a dog like
now I'm imagining Thor's sense of the world and his place in it is like a spatial awareness that depends on smell that's fascinating wow I don't even know I can't grock this fully yeah I I mean I think it's impossible to grock it's UNG rockable have you come across this term umelt no it's a term that comes from this German bi ologist whose name I can't remember right now but it's something I couldn't pronounce even if I could remember itob Johan and umelt it refers to the different realities experienced by different organisms the set of
things that are meaningful to them some of which we can't even sense you come to see that we're just seeing like but one of many worlds which are existing in parallel and other animals are seeing in another slice our rainbow might be more varied than that of a dog but their old factory world is so explosively col ful that it wouldn't occur to them for a second that there's something that's being missed this is it really does help me understand my little best friend better I feel I feel like I I feel connected to his
world and sort of an appreciation that his world is different and also beautiful I don't see Rowdy in his box today but you're also a cat guy can cats do the booping test I find it hard to believe that might be my my stereotypes about cats but have people investigated this and what do we know about cat color vision well hey everybody it's Adam from The Future it's the next morning I've got Rowdy back with me um and I've been up all night reading cat studies
