In page 19 of the stm tutorial, Figure 6: Graphical display of topical prevalence contrast

https://cran.r-project.org/web/packages/stm/vignettes/stmVignette.pdf

How to change the font size of the custom lables of Figure 6 (i.e., font size of ‘Obama’, ‘Sarah Palin’, ‘Bush Presidency’ become smaller / bigger)?

I’ve tried to added text.cex to the code, but has no results.