Why do the extinct Tasmanian Tigers keep popping up?

But on Feb. 23, Neil Waters, president of the Thylacine Awareness Group of Australia, promised conclusive photographic proof of a surviving thylacine. The four photos, he claimed, showed a family of thylacines, including a juvenile, moving through dense brush. The announcement kicked off a flurry of excitement among wildlife aficionados.

But, analysis by thylacine specialists rapidly debunked the photos as a case of mistaken identity. The event is the latest in a tradition of extravagant claims about photographic or video evidence of lost or unknown species that don’t pan out. Why do these cycles occur so regularly, at times even convincing experts? The answer, psychologists say, may lie in quirks of the human mind and how we process information that is at once familiar and difficult to perceive.

While such footage occasionally turns out to be a hoax, many stills and videos genuinely show real animals — even if they aren’t what people say they are. In 2005, a WWF camera-trap caught footage of a “mystery carnivore” — likely a flying squirrel — in the jungle of Indonesian Borneo. In 2007, 2011 and 2014, clips of hairless dogs and raccoons in Texas were described as chupacabras. The same year, a kayaker recorded footage that purported to show an extinct ivory-billed woodpecker in an Arkansas swamp, provoking heated coverage and broad scientific interest. Many experts eventually concluded that the bird was more likely a pileated woodpecker.

Susan Wardle, a neuroscientist at the National Institutes of Health in the United States, says that cycles of expectant belief undone by deeper analysis may in part be explained by human psychological quirks.

Processing every individual sensory detail is impossible, she says, so our brain actively reconstructs our visual world based on the complex but ambiguous input received by our eyes. Research has shown that unclear sensory data — such as a blurry picture — causes the brain to rely more heavily on preconceived patterns to make sense of it. “This means that there is an interesting interaction between perception and cognition — our beliefs and prior experience can influence what we see. Or more accurately, what we think we see,” Dr. Wardle said.

This tendency can lead people astray when studying photographic evidence of long unseen animals, sometimes called cryptids, especially if they already have an idea of what they’re looking for. Many people who go looking for such enigmatic creatures have an emotional investment in identifying them, “and are already convinced the creatures are already out there,” said Christopher French, who founded the Anomalistic Psychology Research Unit at Goldsmiths, University of London, and recently retired.

Said Darren Naish, a paleozoologist at the University of Southampton in England, “These kinds of mistakes are common, in part because even experienced outdoors people and researchers aren’t always adept at identifying animals from unfamiliar angles or in unfamiliar states.”