Google releases a new API, which will allow visitors 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.
Read more here - http://googleonlinesecurity.blogspot.com/2014/12/are-you-robot-introducing-no-captcha.html
To adopt the new reCAPTCHA for your website go here - https://www.google.com/recaptcha/intro/index.html