A number of interesting perceptual principles can be seen according to this realistic sketch. First, objects parallel to the field of vision appears flat and retain their appearances. The circles on the bottom of the sketch provide the best example. Circles directly in front of the eyes appear to be circle while those located at an angle to the eye appear to be ellipses. Nevertheless, we perceive them all as circles. That is the principle of shape constancy. In addition, on the left, where the librarian is sitting working with the computer, the table is actually a curve. Drawn accurately, however, it is a line. Nonetheless, we perceive it as a curve because other points of view, our brains knows that it is a curve rather than a horizontal line.
Second, when a group of entities occur near each other, we perceive them as a whole, even though they do not necessarily behave that way. In this case, however, the three students standing in front of the book shelf do indeed have a conversation. Third, interposition can also be seen by looking at these students. The fact that they block our lines vision to the book shelf indicates that they must be in front of it.
Fourth, from certain points of view, lines that are in reality parallel appear to be converging. This is called linear perspective. The edges of the board on the right with circles on it serves as an example in this case.
Tram’s Sketch in the library is very similar to mine. Unfortunately, however, the photograph of her sketch is not available with a larger size and retains quality. We sat in different places but our field of vision cover a lot of things in common. The concept of relative size is the most obvious therein. Circles far away appear to be smaller although we perceive them as having the same size. I do not know whether the two students on the far side of the sketch were conversing. However, by the Gestalt law of proximity and law of common fate, the brain tends to consider them as a single group.
An illustration of the Gestalt laws of perception other than the law of Pragnanz is as follows.