Knowledge representations and mental models from graphically presented information were investigated for 98 college students with different levels of mathematics experience. The subjects were drawn from a remedial algebra course (n=35), a second semester calculus course (n=35), and a calculus-based statistics course (n=28); they were all exposed to 40 graphical stimuli of bar graph variations. Subjects were asked to judge the typicality and readability of each stimulus. To judge these qualities, subjects required a working model of graph comprehension and a model of concept formation and structure. Results confirm that both memory processes and perceptual processes affect the views of subjects concerning how easy or hard each graph was to read and understand. Individuals of different mathematics experience had different views of the typicality of bar graph stimuli, with increasing complexity of conceptual structure with increasing experience. Nine figures present study data. A 17-item list of references is included. (SLD)