From misremembered childhood moments to mistakenly “recalling” that you took your pills when you didn’t, false memories are surprisingly common. New research suggests we might be able to do just that—by watching the eyes. Then came a curious discovery in the 1970s: people’s pupils also dilated when they recognized something they’d seen before. When people recognized a word they’d seen earlier, their pupils dilated—and the effect was more pronounced when participants could precisely remember the word’s original location. This suggests our eyes reflect two layers of memory: a general sense of familiarity, and the precision of specific details, Albi tells Popular Science.