Ad personalization is on by default. The checkbox that says: > Also use Google Account activity and information to personalize ads on these websites and apps a

Ad personalization is on by default. The checkbox that says: > Also use Google Account activity and information to personalize ads on these websites and apps and store that data in your Google Account Should be off if you didn't opt-in though. I just tested it with a new Google account and it was off after I opted out.