‘I knew that was going to happen:’ Déjà vu and the ‘postdictive’ bias

When intense feelings of prediction accompanied déjà vu, they were strongly correlated with feelings of postdiction that happen afterward. High degrees of familiarity that accompany déjà vu also carry through to postdictive bias.

For many, déjà vu is just a fleeting, strange sensation that “I’ve been here before.” For others, it gets even more unreal: In that moment of unsettling familiarity, they also feel that they certainly know what’s going to happen next – like, a girl in a floral print shirt is going to pass me on the right.

And when the girl in the floral print shirt really does pass by, well, what can explain it? Sign theories of previous lives, clairvoyance, and the supernatural.

How Lab Experiments Reveal Déjà Vu: When Prediction and Postdiction Happen Together

Anne Cleary, a memory researcher at Colorado State University who is one of the world’s experts on déjà vu takes help of laboratory experiments to induce déjà vu in human subjects. The researchers have a new theory on why déjà vu takes place not only by feelings of prediction, but also an “I knew that was going to happen” feeling a minute later.

To examine that theory in the lab, Cleary and co-authors involved a bank of test participants in a video game-like scene created in the Sims virtual world.

The study asked participants if they were experiencing déjà vu. Next, the virtual scene would turn right or left. Then, the experiment asked subjects if the scene matched their expectations. In a later experiment, participants rated the scene’s familiarity before and after the turn to assess their perceptions.

After analyzing their results, researchers discovered that intense feelings of prediction during déjà vu often align with postdiction experiences. Participants reported knowing specific outcomes after the fact, such as which turn was about to happen.

The study’s design aimed to test this connection by incorporating random turns, making it impossible for participants to predict accurately. Despite this, the alignment between prediction and postdiction remained notable.

The experiment highlights how déjà vu connects with predicting events, even when researchers randomize the predictions.