The logic that dogs use

I’ve been reading up lately on databases and the logic that makes them work. I came across this expression in a SQL tutorial book this morning that cracked me up:

Most of the better DBMSs will not even evaluate the second condition of an OR WHERE clause if the first condition has already been met.

It’s a reference to the logic rule called “disjunctive syllogism” that I learned about when I was briefly a logic major in college. Simply put:

“A” or “B”
Not “A”
Therefore “B”

What made me laugh was that I remember my professor saying this reasoning was so innate to existence, that even dogs employ this rule when hunting. I clicked around a little, and found a 500 year-old observation of this phenomenon. When tracking prey by scent, if the trail forks, and the dog doesn’t immediately get the scent when testing one side, he sprints down the other path without bothering to sniff for the scent.

I guess we’ve finally taught computers to do what any dog can do easily.