In coding we give cookies to the registered user, or to mark preferences or for thousands of other things.
We never give cookies to the robots, because no robot will take cookie to mark itself as a robot.
Then why not giving cookies to the human users?
If the user doesn’t hold a cookie it is to show that this user is not human. There are many ways to give cookie to human and one only way for the robots - find it. But we can help robots to find the wrong cookies.
TruBar is a plugin that asks anonymous users to click on a link before posting a comment or registerering on a weblog.