Official 13 Task 3
Reading

Perceptual Constancy
 

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.

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Narrator: Now listen to part of a lecture on this topic in a Psychology class.
Professor: Let's take an everyday example -- an ordinary round plate 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're 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's a different object,
not the same plate?
Of course not.
It looks different,
but we perceive it as still being the same.
Here's a different example.
This classroom we're in its 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 roll, right?
But let's say you're sitting in the front row today,
but tomorrow you're sitting in the back row.
From back there, I'm going to look smaller,
but you don't think I've actually gotten smaller.
You don't think you're seeing a different professor,
a guy who looks like me except he is smaller.
No matter where you are, up close or far away,
you understand without even thinking about it that I'm the same size, the same person.
Question
Explain what is meant by perceptual constancy using the examples provided by the professor.