I shall call the following figure the duck-rabbit. It can be seen as a rabbit's head or as a duck's. And I must distinguish between the 'continuous seeing' of an aspect and the 'dawning' of an aspect. The picture might have been shown me, and I never have seen anything but a rabbit in it.
Here it is useful to introduce the idea of a picture-object.
For instance would be a 'picture-face'.
In some respects I stand towards it as I do towards a human face.I can study its expression, can react to it as to the expression of the human face. A child can talk to picture-men or picture-animals, can treat them as it treats dolls.
I may, then, have seen the duck-rabbit simply as a picture-rabbit from the first. That is to say, if asked "What's that?" or "What do you see here?" I should have replied: "A picture-rabbit". If I had further been asked what that was, I should have explained by pointing to all sorts of pictures of rabbits, should perhaps have pointed to real rabbits, talked about their habits, or given an imitation of them.
Imagine the duck-rabbit hidden in a tangle of lines. Now I suddenly notice it in the picture, and notice it simply as the head of a rabbit. At some later time I look at the same picture and notice the same figure, but see it as the duck, without necessarily realizing that it was the same figure both times.—If I later see the aspect change—can I say that the duck and rabbit aspects are now seen quite differently from when I recognized them separately in the tangle of lines? No.