Even with all the training in the world, there are still some perceptual quirks that you can't unlearn...

Here's an interesting experiment that you can conduct without even getting up from your chair:
- Keeping your hands parallel with your shoulders, stick up both your thumbs, and hold one at arm's length, the other level with your elbow.
- See how big the near one looks compared to the far one.
- Now converge them so that they overlap.

What should happen is that the near thumb simultaneously 'grows' and 'doesn't grow', but ends up appearing much larger than it did when it wasn't overlapping the far thumb. What appears to be happening is that far away objects are percieved as being much larger than they actually are, as long as this wouldn't make the 'image' inconsistant. This scaling (usually) goes unnoticed, but comes in very useful in reading text, recognising faces, etc. at a distance.