In the 2009 post, Google said:
> ...customize search results for you based upon 180 days of search activity linked to an anonymous cookie in your browser... You'll know when we customize results because a "View customizations" link will appear... Clicking the link will let you... turn off this type of customization
None of that appears to be match the study results here. Incognito mode isn't supposed to pick up session cookies from normal browsing, no customization notice appears, and an option to turn the behavior off certainly isn't provided.