Over 30 percent of Americans believe in the concept of reincarnation, the notion that people who die will be reborn again in this world.

While there's no firm scientific evidence suggesting that it actually happens – nor of what happens to our consciousness after we die – the study of reincarnation, and our beliefs about it, is still a serious focus of scientific research.

For decades, in fact, researchers have investigated what's known as Cases of the Reincarnation Type (CORT) – instances in which people, predominantly children, appear to report memories and details of somebody else's life.

Since the 1960s, researchers at the University of Virginia's Division of Perceptual Studies have collected information on thousands of these strange cases, representing the largest dataset of its kind.

Now, a new analysis of that trove of data has revealed a striking pattern in these mysterious episodes.

In cases where the identified deceased individual died suddenly or unexpectedly, the "intermission time" – the amount of time between their death and the birth of the child recalling their life – was significantly shorter than in cases where the death wasn't unexpected.

The findings, reported in Psychology of Consciousness: Theory, Research, and Practice, can't really be explained, researchers say.

"This is the largest systematic study to date of temporal patterns in reported past-life memories," says lead author and cognitive neuroscience researcher Saeedeh Sadeghi from the University of Virginia.

"Individual cases can leave room for different interpretations, but patterns across many cases are much harder to explain as exaggeration, fantasy or fabrication."

In their study, researchers analyzed every case in the Division of Perceptual Studies' CORT archive where investigators had been able to identify a named deceased individual (aka "Past Person") whose life and biographical details corresponded to statements collected from children who supposedly remembered things about the Past Person's life.

"Trained investigators conducted comprehensive interviews with multiple informants for each case, such as the child, parents, close relatives, and sometimes family friends and neighbors," the researchers write.

"Investigators systematically evaluated evidence from multiple sources … to systematically explore conventional explanations of the child's statements as well as the possibility of anomalous ones."

The researchers analyzed 1,678 cases involving an ostensibly identified Past Person, finding that the median intermission time was 16 months among the 1,319 cases with available timing data.

But the more unexpected the death was – whether due to an accident, violence, or a sudden medical crisis – the shorter the intermission time tended to be.

In cases where the death was completely unexpected, the median intermission time was only 12 months, reflecting a roughly 43 percent reduction from the most anticipated deaths (21 months).

What's more, the effect remained when the researchers accounted for a range of other factors, including the quality of the verified information, the level of accuracy of children's statements, prior acquaintance between families, social status, and religious beliefs.

"The effect remained even after we accounted for several cultural and psychological factors, and it was actually stronger in families whose religions did not support reincarnation," says social psychologist Philip Cozzolino of the University of Virginia.

"These results do not support the idea that social beliefs are driving this pattern."

Of course, none of this should be taken as evidence that reincarnation necessarily occurred in these instances, and the researchers acknowledge that the strength of the observed association was modest, with death unexpectedness accounting for only about 2–3 percent of the variance in intermission time.

Still, the fact that the pattern can be seen in the data is hard to explain, the researchers say, noting it's not something that can be accounted for by existing psychosocial mechanisms.

"The noteworthy finding is not that death circumstances strongly predict intermission time, but that they predict it at all – despite the absence of an established conventional mechanism linking the two," the team explains.

While that's the case, the researchers observe that many cultural and religious traditions from around the world are imbued with concepts that treat unexpected deaths as leaving unfinished business on the part of the deceased.

"Across a number of reincarnation-oriented traditions – including Hindu, Buddhist, and Indigenous North American frameworks – abrupt or premature death may leave unresolved intentions, attachments, or obligations, creating a stronger impetus toward rebirth," the researchers write.

Even outside the scope of reincarnation belief, many cultures view people who die violently or suddenly as remaining more closely connected to the living world.

We don't know yet whether these kinds of cultural beliefs somehow influence the patterns observed in reported past-life memories, but future research into this strange phenomenon might provide some answers.

"Is this evidence of anything metaphysical? The data are observational and we're careful to stay agnostic about mechanism," Sadeghi says.

"What I can say is that the pattern is real in the data, and not readily explained by cultural and psychological factors we examined – which, to me, is a reason to keep looking, not to look away."

The findings are reported in Psychology of Consciousness: Theory, Research, and Practice.