This report uses mental model theory to create a taxonomy of picture functions in order to relate these functions to learning theories. A rough outline of picture functions is presented, consisting of a retrieval function, a focus function, a construction function, and a supplantation function. It is suggested that this taxonomy could be helpful in elaborating a "grammar of pictures" since pictures may have to be designed differently according to their intended function. It is recommended that prescriptive hypotheses based on this taxonomy be created and tested empirically. (8 references) (EW)