I don't have cats nor dogs. However, I observe my cat's neighbour in their yard (from the third floor of my balcony). My neighbour always puts a long string so the cat can wonder around in the yard. However, I always found that within such a short time, the rope is getting tangled (under the chair's legs, around posts, etc). It always ended up that the cat only has about a few feet of free rope (ie. get stuck).
I actually wonder if it would be the same situation for a dog. I recall seeing a TV program about how smart an octopus is (where she can move around and try to go inside a chamber through a series of tube openings to get food). So, comparing to this sea creature, I wonder about the intelligence of a cat.
Watching my neighbour's cat always frustrates me. Why can't the cat follow the end of the rope and free herself from the tangles ? Or perhaps she does not want to free herself up! Could this actually be trained in a cat, just like training the cat to use the litter box ?
In contrast, however, I also heard that unlike a dog, cats can ration themself when they eat. So, you can left a supply of food and the cat won't eat all at one time like a dog... and get hungry later.
Just a curious observation !