I am considering adding badges to a course I am developing to try to get the students to try new things, and acknowledge constructive behavior.
I have seen badges employed in two ways:
all of the badges and what you need to do to earn them is described up front (e.g., Stack Exchange)
all or some of the badges are secret until you earn/unlock them
What are the relative strengths and weakness of each of these approaches and which would be better suited to an educational setting?
Edit: To clarify a point made in the answers. The badges will not be tied to the grading/evaluation in any way. They will be used as a bit of fun and motivation just like they are used here on SE. The grading/evaluation will be completely transparent and described in the syllabus.
( 4 months ago )
If all of them are "hidden", then it discourages the initial "buy in", but if all of them are "visible", then users will tend to just do what's needed to get the badges.
Mixing them up is a good solution, with easier badges visible right off to get the initial buy-in (in some cases a "you pressed the start button!" badges), and then some hidden to encourage exploration.