Google’s ‘No CAPTCHA reCAPTCHA’ is designed to identify whether you are not a robot. The new tool isn’t overtly labeled as a Google service, yet anyone clicking through it to be tracked by Google’s cookies, AdTruth found. Google told Business Insider the signals the new tool examines are not used for ad targeting and that the tool does not analyze specific user interests or preferences. Google says its risk assessment software uses behavioral cues, such as where users click, how long they linger over a checkbox, and their typing cadence, to work out whether they are human.”]
Source: https://www.businessinsider.com/google-no-captcha-adtruth-privacy-research-2015-2