Tuesday, October 30, 2007

Illusion Explained

Sorry to have left this picture up here without any explanation. I was just using the blog as a bulletin board to tack it up. It was the follow up to comments I made on Whose Planet Is It Anyway. You see, my esteemed fellow blogger, the Autistic Bitch From Hell, posted a link to an article about moving version of this. The article said that the dancer spun in one direction for some people and in the opposite direction for others.

The thing is that, when I watched it, it spun first in one direction and then in the other. The timing seemed random. Looking at the comments on the main article, I noticed that I was not the only person to have spotted the truth. It was, in fact, quite clearly spinning in both directions with a random timer determining when the direction would shift. Gullible people would see it moving in one or the other direction and think that, because different people saw it at different times, there was some kind of weird perceptual thing going on, when in reality it was just a bit of cleaver programing.

I was so convinced of this -- after all, I had seen it with my own eyes -- that I posted a comment to that effect. Then it occurred to me to take it apart and find out how the trick worked. So I did.

It turns out that there was no trick. It's an animated gif that presents a 36 image sequence in the same order each time. The still bellow is one of the images. My brain just happens to processes that sequence as moving in both directions, and just happens to reverse the direction it thinks it is moving in every few seconds, in a way that looks random.

What is really fascinating about this is how absolutely sure I was of the veracity of what I saw. It did not fit with the explanation I had been given and, say what you like, I had seen it with my own eyes.

You know what this reminded me of? MK's teacher from last year. She'd seen what she had seen, and you could talk until you were blue in the face, she had incontrovertible evidence in the form of her own observations that things could not be as MK's parents claimed.

The next time I set out to educate someone, I'm going to try to keep in mind that seeing is believing.

1 comment:

abfh said...

Cool... it's easier to see from the still figure how the moving illusion is done.