What's that up in the sky? Is it a …?

I am writing this just before Christmas so there is the inevitable discussion in the media about strange sights in the sky. An example was a television show about the star that the Magi (who don't seem to be called that anywhere in the Bible) followed to find the baby Jesus. Scientists with impressive qualifications looked at all the available evidence and decided that the star was almost certainly a conjunction of Jupiter and Saturn (with both planets close together and reversing their direction in the sky at the same time), or Jupiter being eclipsed by the moon, or a nova appearing behind Jupiter (and perhaps Saturn as well), or a comet, or Jupiter (again) rising at dawn, or something happening in Pisces (the sign for Israel, a place which didn't exist at the time so perhaps it was really the sign for Judea), or something happening in Aries (the sign for the Jews), or … .

So much certainty, and so many possibilities. It reminded me of the way experts suddenly appear to explain other unexplained sights in the sky, those mysterious "unidentified flying objects". A few weeks ago the world was gripped by stories of a major UFO sighting over Norway. There were shaky videos taken with mobile phone cameras, still pictures showing weird lights in the sky, highly professional videos with very clear focus that suggested that someone had fortuitously placed a high-quality camera on a tripod at exactly the right place (or maybe did some work with video editing and graphic creation software) and many other pieces of evidence. Authorities declared that aliens had obviously arrived and were twirling around in the clouds. (Probably as practice for creating crop circles. A circle in a Norwegian pine forest – I'd pay to see that.) Other authorities were sure that a wormhole had opened into another dimension, if not another universe, perhaps to let the aliens through. The possibility of a black hole escaping from the Large Hadron Collider was raised. A suggestion that perhaps a Russian missile test had failed was shouted down because wormholes and aliens were much more likely.

Did I mention that a few days later the Russians came out and said, with much "umming" and looking at the floor while they drew patterns in the carpet with their toes, that there had indeed been a test firing that night and, yes, it had failed, and, yes, it had spun around a bit making a spiral cloud from its exhaust? The UFO story seemed to disappear the next day.

Humans need to explain what they see and hear, which is why we are subject to optical illusions where the brain tries to interpret ambiguous cues. Presented with something unusual or new we automatically try to explain it in terms of our experience and prior knowledge. We have to do this or we would spend all of our time trying to work out what was happening around us, but problems can arise if we approach anomalies or novelties with a predetermined context or a standardised explanation.

One example of mistakes in perception is pareidolia, where people see meaningful patterns in random imagery. Everyone has seen the face of The Man In The Moon or animals in clouds. It only takes a second to see why the two characters :) in an email mean "smile" because we are conditioned to detect faces with a minimum of cues. (it's not just humans. When I typed the colon followed by a right bracket, Microsoft Word immediately changed the sequence to a "smiley-face" character and I had to go back and tell it what I really wanted.) There is a good evolutionary basis for making quick decisions based on little evidence, because those who incorrectly interpreted amorphous shadows in the jungle as man-eating aardvarks and ran away might have felt foolish at times but they lived to reproduce. Scoffing skeptics got eaten.

Pareidolia gets weird when people apply certainty to their perceptions, and this is most noticeable in the many ways that religious images appear in the most unlikely of places. Why Jesus should choose to reveal himself in scorching on a piece of toast or his mother decide to turn up as a wet patch on a leaking wall is a mystery to non-believers, but these are just extreme cases of people seeing what they want to see.

UFO believers apply a different error, which is something like the Argument From Personal Incredulity. There is something in the sky that they don't understand so again they see what they want to see, except this time the perception comes from their belief in flying saucers rather than a belief in an interventionist deity. It looks like a spaceship might look like so it must be a spaceship.

And getting back to the first paragraph, the scientists there were doing the same thing as the "Jesus in a tortilla" believers or the UFO enthusiasts. They were interpreting things in a way which fit their preconceptions. We all have to be aware of this, but as scientists and skeptics we are very aware and never fall into the trap.

Do we?

This article was published as the Naked Skeptic column in the March 2010 edition of Australasian Science