Unfortunately, the large difference in F-measure between the Foltz algorithm and the Hearst + LSA algorithm is more difficult to explain. These two methods differ by their segmentation criterion and by their training (Foltz is a regression model and Hearst is not). It may be that<cite> Hearst (1994</cite> Hearst ( , 1997 )'s segmentation criterion, i.e. depth scores, do not translate well to dialogue.