When I heard a long segment reporting on the recent UFO sighting over Stephenville, Texas on NPR I knew this was one UFO story that was getting a lot of media play. Such sightings are common, and often make a small splash in local media, but for some reason this story was making the mainstream media rounds.<\/p>\n
This ABC article <\/a>reports:<\/p>\n The residents of Stephenville, Texas, claim to have seen a UFO, described as a mile-wide, silent object with bright lights, flying low and fast. So what was it?<\/p><\/blockquote>\n What did the residents really see? Actually, they do not describe seeing a spaceship or any kind of craft or even a solid object. What they saw, by their own accounts, were lights in the sky. Common optical illusions and a dab of imagination did the rest.<\/p>\n <\/p>\n Common human experience grossly underestimates the degree to which visual information is processed by the brain. Three-dimensionality, distance, size, and movement are not characteristic that are objectively perceived by our vision. Rather, the visual cortex takes a small 2-dimensional image from the retina and then processes that information to infer things like distance and size. This process is not perfect, and is dependent upon the brain making assumptions about what it thinks it’s seeing.<\/p>\n Here is a clever video <\/a>by Richard Wiseman demonstrating this principle. If you think something is big your brain will interpret visual information according to that assumption and make the object appear to you as if it is farther away. There are a host of optical illusions based upon tricking the brain into making a false assumption about size, distance, or the relationship of objects to each other and then constructing a visual image incorrectly based upon these wrong assumptions. Optical illusions are fun and fascinating because they are so compelling and seamless – until the illusion is broken you simply cannot tell how wrong your visual model of what you think you are seeing is.<\/p>\n Let’s bring this back to the whole question of UFO’s. Sightings like the one in Stephenville are typical in that they involve ambiguous visual stimuli. The sighting was of lights in the sky without the benefit of any other objects for background or reference. Without a reference point – something of known size and\/or distance in front of or behind the lights – for an object that is novel and unknown your brain will simply not know what assumptions to make about size, distance, and velocity. So it is likely to get it wrong, creating an optical illusion.<\/p>\n Therefore, the residents of Stephenville who sincerely thought that what they saw was huge (a mile across), far away, and fast moving may in fact have been something that was small, close up, and slow moving. No matter how certain the witnesses are about what they think they saw, the simple fact is that they cannot know that they were not victims of a seamless optical illusion.<\/p>\n There is likely another optical effect at works here as well. Another aspect of visual processing is to enhance edges to those places where one object ends and another beings. Also, there is automatic visual processing that “connects the dots”, or fills in apparently missing visual information. Therefore, lines that are suggested or assumed to be present based upon what we think we are seeing will be filled in.<\/p>\n If the witnesses were seeing a series of unconnected lights but assumed they were part of one giant object, then they may have “seen” the assumed object, or thought there were lines connecting the lights together.<\/p>\n So the eyewitness evidence that we have is completely compatible with a series of lights in the sky over Stephenville. We cannot make any conclusions about size, distance, or speed, nor can we conclude that the lights were part of one giant object. The other piece of information we have is that the lights were silent. With this in mind what are some possibilities?<\/p>\n