Google introduced a new method that verifies you are human without you having to solve a riddle.

On websites using this new API, a significant number of users will be able to securely and easily verify they’re human without actually having to solve a CAPTCHA. Instead, with just a single click, they’ll confirm they are not a robot.

It looks like this:

http://googleonlinesecurity.blogspot.nl/2014/12/are-you-robot-introducing-no-captcha.html