The simplest way of using type to express more than what has been written by the author of a text is by sudden changes in the character shape. When one word within a sentence is made conspicuous by printing it more boldly than the surrounding words, a cue is given that the word in question should in some way be given more attention. As mentioned in chapter 2, bold, italicized and upper case lettering have each been conventionalized for specific kinds of emphasis in text. An example of this paralinguistic function is the use of italics when a new term is introduced. However, if italics were used to stress names and proverbs as well, the effect of emphasis would be weakened and confusion would soon set in for the reader. Because of this, Hartley (in Britton and Glynn, 1987) states, one style of type should never be used for different kinds of emphasis and only a limited number of different kinds of emphasis can be used successfully in a text. Hartley apparently expects that readers will not distinguish between all kinds of emphasis unless explicitly asked to do so in the introduction of the text. However, Tinker and Paterson (1946) conclude that change of pace is often desired by readers. Change of pace is the use of several typefaces, styles or typographic arrangements in one text. Despite the fact that readers find some variation pleasing, Tinker and Paterson found that it also reduces readability considerably. This supports the notion that the number of different kinds of emphasis employed should be limited. Put another way, variance of type is in conflict with transparency. There are, however, specific situations in which sacrificing transparency would be wortwhile. For instance, Coles and Foster (1975) found that, when the text matter has to be committed to memory, underlining of relevant parts increases immediate comprehension. Concluding from this discussion, it seems best to use a different typeface for paragraph headers, but in general to vary type conservatively and only where it has been objectively proven that it will facilitate comprehension (in a learning situation, for example).

In comparison with emphasis, finding rules of thumb for other kinds of conventional associations is less straightforward. While a sign saying corresponds with our expectations, it is difficult to determine how the convention has come about, since such lettering is no more typical of traditional Irish print than it is of German print, for instance. Investigating this matter is further complicated by the fact that conventions may vary between cultures.