It's easy to assume that our cats see the world in exactly the same way as we do - except perhaps from a lower angle and with some night vision thrown in for good measure. But is that really true? I mean...can they actually see birds in trees when they look out of the window? Can they watch TV? Do they recognise our faces, or just our scent?
This week's Sunday Read explores how our cats see the world. The results are truly surprising - not just in terms of what our cats can and can't see, but also because they offer up explanations for some of our cats' oddest behaviours!
What do cats see when they look out of the window?
Cats seem to be drawn to windows. My two love parading up and down any windowsill they can find, surveying the world outside and chattering furiously at the birds (find out what that's all about here). So what exactly are they seeing when they look out of a window?
Well, this has blown my tiny mind - but the answer is - not very much at all!
It turns out that the lenses in cats' eyes only really allow them to focus on an object clearly if it's closer than 6 metres (20 feet). Anything further away than that becomes an abstract sort of blur (Little, S. 2011).
To put that into perspective, our eyes are able to focus up to 30-60 metres (100-200 feet) away, so our cats' long distance vision is a staggering 5-10x worse than ours. They would fail the 'read a numberplate' part of the UK driving test, every time! (Do other countries have this too? I'd love to know!)
I've found that if I leave an upstairs window open, both Lola and Lyra have a horrifying habit of standing on the edge and leaning right out to stare at the ground below. It looks like they're about to hurl themselves out, and it scares me so much that I've now stopped leaving windows open far enough for them to do this.
Now that I know about their extreme short-sightedness, this weird habit finally makes sense - from the first floor of our house, which is about 5-6 metres high, the only bit of the ground that's close enough for them to focus on is the bit that is right underneath the window. No wonder they try to crane their heads out to take a look!!!
But that's not the only difference between our cats' vision and ours. They also appear to lack the ability to easily discern between shades of red and green, similar to the situation in colourblind humans (Little, S. 2011). For our cats' ancestors in the wild this wouldn't have been too much of a problem - they would have hunted at dawn and dusk when the light is low anyway, and it's not like there is a big colour variation in their shades-of-grey prey (unlike for monkeys, say, for whom being able to pick and eat the red berries while leaving the green ones is pretty critical).
The result is that if we could see the world through our cats' eyes we would think it looked a little washed out, and skewed towards the blue and yellow part of the spectrum. This surprised me too. Lola's favourite toy is a fishing rod with a black and red feather on the end. It's strange to realise that to her it probably just looks black and grey!
Finally, we should talk about field of view. This measures how big a slice of the world you are able to take in without moving your head. In humans, this figure is 180 degrees, which is basically a semi circle. So if we look straight ahead we can see a semi-circular slice of the world in front of us (it blurs towards the edges, though, in the area we call our peripheral vision).
For cats their field of view is 200 degrees (source), so they can see over a semicircular slice of the world. Not quite 'eyes in the back of their heads'... but close enough!
Why can't my cat see things that are right in front of its nose?
My mum has always been convinced that her cat Tilly is, you know, a few slices short of a loaf - not the brightest button in the box. Her evidence? Tilly often brings mice into the house with her and then loses them, right in front of her nose. The mice stand there almost taunting her but she doesn't seem to be able to spot them at all!
It turns out poor old Tilly isn't lacking in brains. All cats have terrible vision close up - pretty much everything closer than 25cm away is difficult for them to focus on (source). This explains why our cats often find it hard to take treats from our hand, and why they seem to 'lose' their toys even when they're right in front of their face. They will often prefer to interact with objects that are in this range by smell or touch, and their whiskers help to fill the void left by their blurry close-up eyesight.
In addition, cats have a pretty impressive ability to spot motion, which far outstrips ours. It's particularly useful for them in spotting the movements of speedy prey, like rodents. This also might explain why mice or frogs that are cornered by a cat prefer to 'play dead' instead of trying to run away. If they can avoid activating the cat's motion detecting response, the odds are in their favour that they'll get lost in the close-up blur and the cat won't be able to locate them!
Can cats watch TV?
Our cats' motion detecting skills may be handy for hunting, but how does it influence other parts of their life? One of the biggest impacts is on their ability to watch TV.
The picture on a TV screen refreshes 50 times every second (or 60 times a second if you're in the US). Our eyes 'fuse' those still images together to create an illusion of motion, and it works because our eyes' 'flicker fusion rate' is 50 times a second. In other words, if you show a human 50 or more pictures a second, our eyes won't be able to see the changing of the images and we'll just perceive it as fluid motion.
Our cats' eyes are different. As a side-effect of their amazing motion detecting systems, their 'flicker fusion rate' is around 70 times a second. That means the pictures on a regular TV set aren't displayed fast enough to 'fuse' into a fluid motion, and our cats will instead see them as a staccato 'flip-book' of separate images!
That's not to say that cats can't enjoy watching TV. They can still take an interest in what they're seeing in the still images flickering across the screen, and in the flicker itself. But if you really want to have a night in watching movies with your cat, you need to upgrade to a 100Hz TV set. That way, the flickering pictures will fuse for both of you, and you'll be able to watch the 'flicks' together!
Can cats see in the dark?
You probably already know that your cat has a better ability to see in the dark than a you do - a product of the massive amount of light sensitive rods that are packed into their eyes. But in 2014 researchers at City University in London also discovered that - unlike our eyes - cats' lenses allow ultraviolet (UV) light to enter their eyes (Douglas, R. H. & Jeffrey, G. 2014). This is probably advantageous when it comes to seeing at night, because the more light the better when it's in short supply. But specifically picking up UV may also unlock extra visual skills for a cat.
For instance, urine trails of rodents are visible in UV light, so a hunting cat could follow these trails to find their prey. It also might explain why cats develop strange obsessions with things around the home - such as sheets of white paper, or laundry - as these can contain optical brighteners that would make them stand out more in the UV spectrum!
Does my cat recognise my face?
I've always thought that my cats recognise me and are generally happy to see me, but what exactly are they using to identify me as opposed to anybody else? In 2005, researchers decided to investigate whether cats could recognise human faces, and the results were surprising - when presented with the face of their owner and that of a stranger, cats were only just a smidgen better at singling out their owners' face than if they were relying on random chance (54% success rate). It tells us that our cats can't really recognise our faces, and instead rely on other cues (e.g. the sound of our voices and our scent) to work out who we are. Interestingly, the study also found that cats are still very good at recognising each other's faces - they could pick out a cat they lived with vs. a stranger about 90% of the time! (Lomber, S. & Cornwell, P. 2005)
I hope this week's Sunday Read has been as eye-opening for you as it has been for me! I'd love to hear your thoughts, anecdotes or questions - just leave a message in the comments below, or join in the conversation over on Instagram or Facebook (both @supakitstore).