"But it did exist! It does exist! It exists in memory. I remember it. You remember it."
"I do not remember it," said O'Brien.
You are more likely to doublethink if you are sad, depressed, or recently have experienced something highly disturbing.
Could be caused by a loss of trust in the honesty and innocence of the world, or maybe you're on drugs.
Michael: "The way Andrew whispers to himself sometimes makes me think he's psycho."
Emma: "Stop double-thinking, he's just trying to remember what the homework was or has a song stuck in his head."
Krystal: "When I found out my boyfriend was a pedophile, I started to doublethink everything my friends and relatives say and do. Maybe they're secretly creepers too."
Jose: "Holy shit. You need help."
(But in the book 1984, doublethink is more of a serious act of course)