An empirical investigation was conducted on the characteristics of language use in graphics communication settings. Graphics communications, such as dialogues using maps, drawings, or pictures, provide people with two independent systems of representation, spoken language and graphics. Drawing on our dialogue data, we show that the presence of a graphical representation significantly changes the way the spoken language is used, extending its expressive capacity in most cases. As two remarkable uses of language affected in this way, we report the phenomena of mediated reference and dual description, illustrating them with actual examples from our data. Further, a quantitative analysis of our data shows that these special uses of language are indeed as common as conventional uses of language in the presence of graphical representations.