The privacy-focused search engine DuckDuckGo conducted a study during June 2018 which allowed it to take a closer look at the way Google is editorializing the search results for its logged in, logged out, and incognito users.
Although DuckDuckGo's study could seem quite biased given that they are a direct competitor to Google, their findings are interesting for anyone who wants to get a closer look into the search giant's inner workings.
Moreover, according to the study's findings, Google's personalized results will be displayed depending on the personal info it has previously collected for specific users (e.g., search, browsing, and purchase history), automatically adding each of them to a so-called "filter bubble."
Google will use this filter bubble to individually tailor the search results displayed to a user searching for a specific term or phrase, with most participants in the study seeing results unique to them.
Furthermore, even though Google previously claimed that it worked on removing their search engine's filter bubble "feature" which would display only the results users would like, DuckDuckGo discovered, with the help of the 87 volunteers that were part of the study, that "Most people saw results unique to them, even when logged out and in private browsing mode."
Users are trapped in Google's "filter bubble" even after logging out and going incognito
Also, Google displayed search results for some of the study participants that others did not although they were searching while in incognito mode or while being logged out, which should have removed the filter bubble bias which appears when a user is logged in, and the search engine can use the information it knows to provide tailored results.
Using private browsing mode or logging out of one's Google account "simply do not provide the anonymity most people expect. In fact, it's simply not possible to use Google search and avoid its filter bubble," says DuckDuckGo.
This happens because browser fingerprinting techniques and IP addresses can be used to track people even when they believe they are browsing the web anonymously, which could explain why Google still editorialized the search results it displayed to the DuckDuckGo's study participants.
All the data DuckDuckGo collected during the study, as well as the instructions and search results obtained, together with the code used to analyze the information is freely available on its website, ready to be scrutinized and explored by anyone interested in verifying their findings.