Summary: When intense feelings of prediction accompany déjà vu, they strongly correlate with a later feeling of postdiction. High familiarity during déjà vu appears to carry through into a powerful hindsight bias.
Source: Colorado State University
For many people, déjà vu is a brief, uncanny sense that “I’ve been here before.” For some, the experience becomes more strikingly eerie: alongside the familiarity they feel certain of what will happen next—such as a person in a white shirt passing on the left.
When that predicted event actually occurs, it’s tempting to attribute it to precognition, past lives, or other supernatural explanations. Anne Cleary, a memory researcher at Colorado State University and a leading expert on déjà vu, offers a different explanation grounded in cognitive science.
Cleary conducts laboratory experiments that reliably evoke déjà vu in volunteers and has identified a linked phenomenon she calls a postdictive bias: after an event unfolds, people who experienced déjà vu are unusually likely to report that they “knew” the outcome in advance.
Published in Psychonomic Bulletin & Review, Cleary’s recent experiments show that déjà vu is tied not only to a strong illusory feeling of prediction—believing one knows what will happen next—but also to a convincing hindsight feeling that the person’s prediction was correct, even when no accurate prediction was possible.
Earlier studies found that people reporting déjà vu felt certain about upcoming events, but they were not actually able to predict what would happen. That predictive confidence was only a subjective impression. Cleary asked: if predictive certainty is an illusion, why do people so strongly believe after the fact that they had predicted the outcome correctly?
To test this, Cleary and her colleagues used a controlled virtual environment built in The Sims. Participants took short virtual tours and were asked whether they were experiencing déjà vu. Each tour included an unpredictable left or right turn. After the turn, participants were asked whether the scene unfolded the way they expected. In a follow-up experiment, participants also rated how familiar the scene felt both before and after the turn.
The results showed a clear pattern. When participants reported intense predictive feelings during déjà vu, they were also much more likely afterward to claim that they had correctly anticipated the particular turn—a strong postdictive bias. Importantly, the turns were determined at random, so accurate foreknowledge was impossible. The postdictive conviction therefore reflected a memory-based illusion rather than real prediction.
This hindsight bias was strongest when participants rated the scene as highly familiar. In other words, the same intense sense of familiarity that defines déjà vu appears to bleed into a convincing after-the-fact belief that one had foreseen the event. “If the whole scene feels intensely familiar as it unfolds, that may trick the brain into treating the outcome as confirmation that you knew it all along,” Cleary explains. “Because the unfolding event felt so familiar, it can seem as if you had known how it would go—even when that couldn’t have been the case.”
Cleary interprets both the predictive and postdictive components as part of an underlying memory-retrieval phenomenon. Déjà vu, she proposes, results from attempts to retrieve a memory that cannot be fully identified—similar to a word on the tip of the tongue. In earlier studies she showed that when current scenes overlap spatially with forgotten scenes viewed previously, people report more frequent déjà vu.
Cleary was motivated to investigate postdictive bias because it seemed to complete a missing piece in her explanation of why déjà vu often feels clairvoyant. Over more than a decade of interviewing people about their experiences, she has heard many accounts in which individuals—sometimes even fellow memory researchers and skeptics—report being certain they had predicted an outcome. The laboratory findings help explain those subjective reports without invoking the paranormal.
Her research program continues to expand. Cleary is collaborating with neuroscientists at Emory University who study patients with medial temporal lobe injuries; this brain region is linked to seizures and can produce intense, recurring déjà vu in some patients. She is also developing experiments that explore auditory analogues of déjà vu—“déjà entendu”—where a person feels they have heard something before but cannot place it. These auditory studies aim to test whether similar retrieval failures and familiarity-driven biases produce comparable predictive and postdictive illusions.
Source:
Colorado State University
Media contacts:
Anne Manning – Colorado State University
Image source:
The image is in the public domain.
Original research: Open access. “A postdictive bias associated with déjà vu.” Anne Cleary et al., Psychonomic Bulletin & Review. DOI: 10.3758/s13423-019-01578-w.
Abstract
Recent work links reports of déjà vu—the strong sensation of having experienced the present moment before despite knowing otherwise—with illusory prediction. The present study demonstrates a related postdictive bias: when déjà vu occurs, people are more likely after the fact to feel that an event unfolded as they expected. During a virtual tour, feelings of predicting the next turn were more common during reported déjà vu, and participants later showed a postdictive tendency to judge the outcome as having matched those expectations. This postdictive effect was associated with higher perceived scene familiarity intensity, suggesting that an intense sense of familiarity during unfolding events can falsely signal confirmatory evidence of prior foresight. Future research should further explore how familiarity signals contribute to both predictive and postdictive illusions associated with déjà vu.