Perceptual Constancy

<-NARRATOR:-> Now listen to part of a lecture on this topic in a psychology class.
<-MALE PROFESSOR:-> Let's take an everyday example-an ordinary round plat like you'd find in a kitchen.
If you hold the plate directly in front of your face and look at it, what shape do you see?
A perfect circle, right?
Suppose you tilt the plate to a different angle, to a horizontal position, like you are planning to put food on it.
Still a perfect circle?
No, the circle is now stretched out, flattened into an oval.
Do you conclude the plate has actually changed shape, or that it is a different object, not the same plate?
Of course not, it looks different, but we perceive it as still being the same.
Here is a different example.
This classroom we are in, it is fairly large, right?
Now, from up close, from the front row, I appear to be relatively big, bigger than if you were in the last row, right?
But let's say you are sitting in a front row today, but tomorrow you are sitting in the back row.
From back there I am going to look smaller, but you don't think I've actually gotten smaller.
You don't think you are seeing a different professor, a guy who looks like me except he is smaller.
No matter where you are, up close or for away, you understand without evening thinking about it that I am the same size, the same person.