Scientific proof that, in many situations, human beings are fundamentally incapable of knowing and/or telling the truth about the world around them:
"...We showed our volunteers pairs of pictures of faces and asked them to choose the most attractive. In some trials, immediately after they made their choice, we asked people to explain the reasons behind their choices. Unknown to them, we sometimes used a double-card magic trick to covertly exchange one face for the other so they ended up with the face they did not choose. Common sense dictates that all of us would notice such a big change in the outcome of a choice. But the result showed that in 75 per cent of the trials our participants were blind to the mismatch, even offering "reasons" for their "choice"."
There are lots of experiments like this. People were unable to tell the difference between something they chose, and a replacement. Then they made up stories about why they chose the thing that was randomly presented to them.
Researchers are finding these kinds of things all the time. But it does not make me cynical or dismissive of humanity. It actually increases my empathy and tolerance. Confabulation is not a deliberate evil, it is an honest mistake. Our brains are, quite simply, built to tell stories about the world around us, even in the absence of facts. It is unfair to expect people to consistently do things that their brains are not meant to handle. Remembering actual facts of the world, rather than a made-up narrative, is one of those things.
But I still believe in progress and self-improvement. The more we learn about these kinds of things, the better we are able to avoid them and give ourselves better mental processes.