Do I lie to myself to be happy? In your case, Teddy, yes, I will.
After having an argument with this undercover police man named Teddy, Leonard writes on the back of Teddy’s polaroid photo in all CAPS “DO NOT BELIEVE HIS LIES.” He writes this very important note on his photo, along with his license plate number — all this on the basis of a very momentary feeling of anger. He acknowledges that momentary vengeful feeling at the time of recording this note and knows that he’s going “to lie to himself”.
But because of his anterograde amnesia, an inability to form new memories, Leonard instantly forgets this feeling and why exactly Teddy is not to be trusted. In his state of default, he assumes that everything he’s doing is leading him to vindication for his wife. So with Teddy’s picture, notes and facts describing Teddy’s appearance, and the license plate number, and his amnesia working in regularity, he comes to believe that it’s Teddy whose killed his wife.
Getting mad, writing that note out of anger, forgetting that note, re-interpreting that note as a clue to his wife’s rape and murder, and acting on the base of that clue was the model of an individual acting on a memory that has been “tampered with.” I don’t think acting on the basis of a “tampered” recorded memory is limited to just amnesiacs in movies, but actually extends to lots of ordinary, everyday people in real life.
Everyone’s memories are “tampered” or influenced by a ton of factors including but not limited to our moods, our emotions, our values, our cultural environment, the social situation, the weather. We omit and forget tons of relevant and irrelevant details. They can mixed, mashed, conflated, corroborated. These are what we base our judgments on. I doubt anyone would ever say that their judgment has always been perfect, but it seems that there will always be people who make judgments based on their first memories, and hardly ever change them.
That seemed to be the case with a few Chicago Bulls message posters and their opinions on Ben Gordon, obstinately holding on to the idea that Ben Gordon was a “bad defender.” This was an impression most people formed his first year in the league, which he gradually proved to be untrue. However, despite marked statistical and visual improvement in his defense for each of his remaining 4 years with the Chicago Bulls, that did not stop a lot of people from returning to the message boards to relentlessly repeating the meme “Ben Gordon was a bad defender.”