Dog Filtering

I have made an observation that I am thinking of publishing as a peer-reviewed paper in a respected scientific journal. I might even apply for a grant. I'd like to run it by you first...

If you have more than one dog, and they are different sizes (probably works with cats and teddy-bear hamsters too, but they seem to be more uniform in size), you can filter them when they come in the house. Coco is smaller and skinnier than Jake, so if I open the door only enough for her skinny, mischievous shoulders to pass, Jake can't come in. It filters him out like a dog sieve.

This can add up to several long minutes of entertainment when you are bored, trust me. One day I figured out the exact range of door openings for which (Dogs - Jake = Coco) would hold true.

Now, if I could only figure out how to filter out Coco and let Jake in, I might be able to apply for a patent.