Perception has a lot to do with legibility.
The more signals available to be picked up, the easier it is to identify the information. At the same time, if an image is incomplete it is usually possible to determine the meaning by combining the information contained in the image. An interesting example of this concept can be seen in Figure 1, where the base of the letters have been cut off and only the tops can be seen. In the line containing only capitals, it is very difficult to decipher the word, however, the lower case is relatively easy to read. But the legibility of any series depends to some extent not only on the letter-forms but on the way they are arranged and printed.