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.