Wednesday, 1 March 2017

Disappearing heron!

HeronAs a birder, I'm always on the look out for birds when travelling by public transport. It's amazing what you can spot in such circumstances when you try. I've even spotted rare birds in this way. So when I saw the crouching heron from a train recently I was delighted but hardly surprised. What happened next, though, was very surprising indeed.

The 'heron' suddenly disappeared to be replaced by what it truly was, a low white object resembling a (British) fire hydrant sign. I don't know if it really was a sign as the whole scene was soon out of sight. What astonished me was how absolutely perfect this particular misperception was. I was in absolutely no doubt, at the time, that I was looking at a heron and even tried to get a better view before it went out of sight. So when it suddenly changed into something else I was shocked. I've seen a lot of misperceptions in recent years but this was among the very best. I can't recall exactly how the misperception disappeared but it was rapid. The heron in the photo (right) doesn't look very rectangular, like the 'sign' (or whatever it was), but when crouching they have a quite different overall shape.

I saw another striking misperception from a different train just a couple of days later. This time it concerned the fence running alongside the railway. When I looked directly at it, the fence looked unremarkable. But if I looked up, so that the fence went into peripheral vision, the fence became a wall! If I looked back it was a fence once again. And if I looked up again, it became a wall again. As such, it was an unusually robust misperception.

Of course, misperceptions are quite common in peripheral vision but usually they disappear once you've seen them in central vision, even if you subsequently view them in peripheral vision again. I wonder if the motion of the train was adding to the robustness of the misperception. It makes me wonder if witness or object motion might be another misperception trigger? It would make sense as the other triggers limit how well an object is perceived.

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