How an object affects our senses depends in part on external conditions, and these conditions are always changing. An object viewed from one angle presents a different shape to our eye than when viewed from another angle; similarly, as the distance from which we view an object changes, the object will appear larger or smaller. In spite of this, even as conditions change and we see objects differently, we still recognize that they remain the same. This is what is known as perceptual constancy. If not for perceptual constancy, we might have difficulty recognizing familiar objects if we viewed them in a new and different context.
<-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.
Explain what is meant by "perceptual constancy, " using the examples provided by the professor.