They go into detail on that in the "Knowns, Unknowns, and Emerging Controversies" section. Further questions that knowledge can help us answer include:

* How do stereotypes form?

* Why are some stereotypes not accurate? They mention nationality stereotypes in particular as being quite inaccurate.

* What other factors correlate with increased or decreased stereotype accuracy?

There's some value, of course, in just learning something's true even if it's not immediately useful knowledge.