Google has used various methods to distinguish between human and bots on the web all this time. Its take on the CAPTCHA test, called reCAPTCHA, has needed you to transcribe distorted words, confirm Street View addresses or tick a box. But you will not have to that anymore soon. Why? Well, Google's making the system invisible now.
Google has updated its system to detect user habits without dedicated interaction by using a combination of machine learning and advanced risk analysis. As soon as you get on a page the controls should disappear and serve the related content. But if you do trip Google's risk analysis algorithms, you may have to solve one of the search puzzles fast.