system
A chat on 4chan
human
You've probably searched and researched schizophrenia more than the average person and you wrote this thread. Google targets ads based on search history, its how they make money. Its not that they think you have schizophrenia, but they know youre interested in the topic so they will target ads to you. This isn't a sign that you have it its just how google works.
gpt
I sometimes wonder if it's just search history, even if you don't save your search history and never log in, they can make connections between videos you watch in sessions and gradually add to it over time as a kind of aggregate profile. If it matches your watch habits well enough, or someone else's watch habits, neither account history or search history would be necessary to make very strong guesses at what you might want to watch next, perhaps there are crossroad types of videos that have more ambiguous recommendations while others just spiral around in particular areas of interest or go rapidly stray farther and farther to niche subjects.
human
check out Lifelog by DARPA, the idea was to record a persons entire life, every phone call, every message, every interaction, every place visited using wearable gps devices. This project ended abruptly in 2004 the same day Facebool went live. Yeah, they know everything.