Instructional time to high proficiency or response time to high proficiency performance can be viewed as linearly related to the effective complexity of the task/display combination which is the essence of instruction or of performance. This proposition is concretely illustrated for bar graph-using performance of 4th and 6th graders who under most conditions manifest quite accurate performance. Mean response time (T) is made a linear function of the measure of task/display effective complexity. A model is presented wherein this measure of complexity represents the sum of the weights of the parameters pertinent to three physical operations, one or more of which is pertinent to performing either of two information processing tasks with respect to either of two bar-graphic display forms. It is contended that effective complexity could be evaluated for any sufficiently analytic information display form using the approach sketched. It is noted that in any such analysis the measure of complexity remains a postulation until empirically verified using suitable new data. (Author/BW)