Brian Williams stepped down amid allegations that he’s a liar liar pants on fire. The popular news anchor cited concerns that he had become too much a part of the news, after being caught in an apparent lie about his wartime adventures.

Williams had claimed that a chinook helicopter he was in had taken fire during a mission in Iraq. Soon after, the pilot of the helicopter questioned his story, saying Williams was in a different bird. Not the one that had taken an RPG round. Williams immediately apologized, blaming foggy memory. The waters were further muddied when said helicopter pilot later expressed that even he wasn’t 100% sure of the details surrounding the event. Just how possible is it that the anchor had truly misremembered that event?

Bear with me here. I tend to give people too many benefits of too many doubts. In this case, though, there is one thing I know for certain: Human memory is terrible. When I first heard about Williams’ fib, I immediately chalked it up to what is called a misattribution memory, where one remembers an event but misplaces a crucial detail. It can happen to anybody. Heck, former president Ronald Reagan famously confused the plot of the 1944 film, A Wing and a Prayer, as something he personally experienced. Think your memory is any better? In this clip from the World Science Festival, Harvard psychologist Daniel Schacter tests the audience’s memory.

One thing I’ve heard people wonder is how he could have recalled such a scary event incorrectly. But the truth is, memories of tragic events are just as likely to be incorrect as everyday memories. Calling them “flashbulb memories”, scientists have shown that tragic events are recalled with vivid clarity, bit not necessarily with indelible accuracy over time. It has been scientifically proven that you probably don’t really remember exactly where you were on 9/11.

So was Williams telling a bald-faced lie? Or are we merely watching a human brain spin a false narrative over the course of 12 years? The New York Times put together this video showing exactly how Williams’ story changed over time, and it’s pretty fascinating to watch.

All that said, Williams is not entirely off the hook. The anchor is also under investigation for several dubious tales he told during his coverage of Hurricane Katrina. If fact checking catches him in a lie again, it won’t be so easy explain away.