Greyhounds have the highest and cleanest breeding lines of any dog. Only the top winners are bred and none in the United States are bred out of the Racing Associations in order to keep lines pure. This also means there is no inbreeding going on whatsoever as everything is documented and the best alleles of the very best genes get passed down, nothing else. Its near impossible to get a puppy for under 10,000 dollars and you are not allowed to breed them freely either. So what you get is a highly intelligent racing machine. They are intelligent to the point of they will consider your needs, but they have a mind of their own and will do what is in their best interest a lot of times first. They contemplate, how will action X, benefit me, whereas some dogs just act without thinking. They are big time opportunists.