Grandma is sure that yesterday's lunch was chicken, even though she actually ate fish. She cooked both dishes recently, and her brain glued them together by meaning: "something tasty in a frying pan." Memory is like two compasses: one points to meaning, the other to the order of events. With age, the needle of meaning starts to outweigh the other.
In one experiment, 90 people learned word lists. Within a list there were words related by meaning, for example "actor" and "cinema." Sometimes these words came one after another, sometimes with four other words in between. Then participants were asked which words they had seen. It turned out that only semantic closeness triggers false memories in everyone: if a word is related to what was there, the brain says "yes, I saw it," even if the word wasn't there.
The difference was in recognizing real words. Young people better remembered words that came next to each other and were related by meaning. Older people remembered only those related by meaning, and order didn't help them. That's why Grandma mixes up what happened yesterday and what happened a year ago, but remembers well that both chicken and fish are food.
People used to think that older adults simply have weakening memory. But now it's clear: their sensitivity to novelty is the same, it's just a different strategy. They rely on meaning, not order. This can be used: if you train attention to details and sequence, false memories will become less frequent. And such errors also help doctors notice memory problems earlier.
Participants scoring below 26 on the Montreal Cognitive Assessment were excluded, so the sample was cognitively healthy. Even in such people, false memories reached 30% under some conditions.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.