He calls it the CAPTCHA Effectiveness Test:
- The test must be able to be administered where the human and the server are remote to each other over the network.
- The test must be easy for humans to pass. Less than 0.01% of humans should fail the test on the first attempt.
- The test must be hard for computer to pass - Computers should have less than a 1 in 10,000,000 chance of guessing the correct answer. (Even after a pre-determined amount of analysis time)
- The test must be able to be completed by a human in less than a several seconds.
- Knowledge a test question, answer, or result (or combination thereof) must not impact the predictability of following tests.
- The test should not discriminate against the blind or the deaf. Or provide a solution to address the issue.
- The test should not possess a geographic, cultural, or language bias.