Psychologically speaking, retroactive jealousy refers to an obsessive curiosity, distress, or jealousy regarding a partner’s past romantic or sexual history. It is that nagging, unsettling feeling of being bothered by people who existed in your partner’s life long before you ever came into the picture. Even though that past is completely over and done with, it somehow feels like a persistent third wheel in your current relationship.

If you’ve ever felt this way, you know it makes you feel slightly crazy. But experts say it’s actually a built-in human reflex, not a character flaw. Licensed marriage and family therapist Figs O’Sullivan explains that it often comes down to “attachment panic.” Essentially, our primitive nervous systems have a really hard time understanding the difference between the past and the present. When you see an old photo of an ex, your brain panics and registers them as an active threat right now, even if they haven’t been in the picture for years. Clinical psychologist Dr. Sabrina Romanoff points out that this isn’t just regular jealousy, it creates an endless loop of rumination in your head. It triggers intrusive thoughts, which act like bad movies playing in your mind that you never asked to watch. To make the bad feelings go away, we start “pain-shopping” like scrolling through an ex’s old Instagram posts or interrogating our partner for just one more detail. The problem is, trying to find more information doesn’t fix it. It just feeds the loop and gives a ghost way too much power over your actual, real-life relationship.