Forty years ago this month, President John F. Kennedy was shot dead on the streets of Dallas. Forty years ago this December, the President’s Commission on the Assassination of President Kennedy — the Warren Commission — began their investigation of the assassination. Forty years ago next September, they made their report. The report ran to 26 volumes and over 5000 footnotes; the National Archives stored 360 cubic feet of the commission’s materials. And still, people feel that the matter is not settled. The ongoing and pervasive belief that Lee Harvey Oswald was not a lone gunman — a "silly little Communist" — might just be a need for meaning for most of its adherents, an outcome of a culture of conspiracy that might tell us something about the conflicted essence of the national story of America. But it seems rather unkind to say that the true believers, those who brush conventional logic aside, are simply searching for meaning. They’re not trying to make Kennedy into a martyr for something larger than himself; they think that they’ve found the traces of something monstrous. Going through 363 cubic feet of documents, how could they not?

The historian of science Michael Shermer calls people "pattern seeking, storytelling animals". Isaac Newton saw patterns in dice; John Snow saw patterns on a map (and invented the science of epidemiology. The human brain is hardwired to recognize patterns, everything from dots on a map to the wind blowing grass through the veldt to the crinkle in another person’s eyes. Making computers recognize patterns, whether printed characters, objects, or human faces, is hard work, but healthy six-month-olds can recognize faces (although skilled birdwatchers apparently use the same portion of the brain while exercising their hobby; it seems to have to do with object recognition expertise).

A medical condition called prosopagnosia can render human faces as similar as stones. The more common problem, however, is pareidolia, in which people see patterns in noise. (Psychologist George Wolford has examined the tendancy of people to find patterns in random sequences, even when they are told that the sequences are random; he credits the left hemisphere). Pareidolia is responsible for us making out faces in clouds in the sky (or in clouds of smoke), the appearance of religious figures in tortillas, ghosts in lights, and a slew of other phenomenena that seem eerie or supernatural. (It may also be responsible for the atrocious accuracy of eyewitness identifications in trials.) The conspiracy researchers who have found the traces that the world wants to ignore aren’t making things up, any more than mistaken eyewitnesses were. They’re looking at a mass of noise, trying to see what’s hidden, seeing what isn’t there.