It’s just a shadow. You can’t really tell if the image is facing forward or backward, but since we are used to people looking at us, our first impression is that the dancer is looking at us. The dancer’s leg is moving left, stops, right, stops etc. If on the split-second your eyes saw the image, the dancer’s leg was moving left – you would think that she was spinning clockwise. If it was moving right – you would think that she was spinning counter-clockwise. From that point, your brain had already decided which direction the dancer was spinning and it would be very difficult to change your mind without looking away. It is about the exact split-second your eyes first saw the image.
This is MY theory:
It’s just a shadow. You can’t really tell if the image is facing forward or backward, but since we are used to people looking at us, our first impression is that the dancer is looking at us. The dancer’s leg is moving left, stops, right, stops etc. If on the split-second your eyes saw the image, the dancer’s leg was moving left – you would think that she was spinning clockwise. If it was moving right – you would think that she was spinning counter-clockwise. From that point, your brain had already decided which direction the dancer was spinning and it would be very difficult to change your mind without looking away. It is about the exact split-second your eyes first saw the image.
How’s my theory?