Tuesday, 9 August 2016

Phantom squirrel?

VigilRegular readers will know that I am a keen nature watcher. So when I saw a small shadowy animal (maybe squirrel-sized) moving around in the distance, in peripheral vision, I instinctively turned to look straight at it. I was a bit surprised to see no animal there, with nowhere it could have hidden in the fraction of a second it took me to turn my head. So, was it a phantom squirrel?

My first thought was that it must have been a misperception but there was no obvious object present to misperceive. Then I saw what I recognised to be the same object moving again. The 'squirrel' was actually a petal blowing around a few centimetres off the ground. So it WAS misperception after all!

This all sounds a bit unlikely until you consider the circumstances. It was early in the day, the sun was low in the sky, throwing long dark shadows everywhere. The petal was barely noticeable until it was caught for a second or so in a shaft of sunlight as it was blown around.

Movement is one of the most important ways by which I detect the presence of wildlife. So when I caught the movement in peripheral vision, my first thought was that it must be a small animal. The moving petal then visually combined briefly with a dark shadow behind. Peripheral vision is, of course, more sensitive to movement than central vision. It also has lower resolution so that physically separate objects can sometimes get combined visually, particularly in high contrast views like the one here.

This incident illustrates the most difficult to detect type of misperception - that caused largely by patterns of light and shadow. If an investigator finds a bush where a witness reports seeing a human figure, it is easy to see how misperception may be the cause of the sighting. But a sighting caused by a pattern of shadows that might only occur for a few hours of a few days each year can be much more difficult to track down. I've only worked out explanations for such incidents when I've investigated them at the time of the sighting. Had I investigated them later I doubt I'd have worked out what was really going on. Maybe some shadow ghost sightings are actually caused by normal shadows.

PS: I caught myself in the act of carefully looking at people's faces in the street twice recently! I just suddenly realised I was doing it. So maybe it IS an explanation worth considering for 'fame month' - see here for the background to this.

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