Do graphs promote learning in principles of economics?

The authors tested whether student performance in the principles of economics course is affected by the use of graphs as part of a lecture. They conducted two experiments at the University of South Carolina, one in spring 1995 and another in spring 1997. Students were randomly assigned to either a no-graphs lecture or a lecture with graphs. The main hypothesis was that students in the lectures with graphs would show higher gain scores than those in the no-graph lectures (both lectures were videotaped). The authors found that students in the lecture with graphs in 1995 had significantly lower gain scores than those in the no-graphs lecture. For 1997, they found no significant differences in student performance between the two groups.