Group work. The carriage parabole

the last week, I read a blog about group work, which  reminds me something that I said to my students every time they have to work in groups. I don't know the new advances in pedagogy, but I always use the example of  the carriage, as shown in the graph, in which the limit for group work is three people.

This number is because in every team with three members of more, there is always the same configuration:

(1)

• The horse: the one who makes all the work. 
• the boss: the one who give all the orders to the horse.
• the freeriders: the one who enjoy all the work done by the team (that is why the happy face)

The typical configuration is 1 horse, 1 boss and 1or more free-riders, and when the total of members is greater than three, the increment of people goes most of the times to the free riders, a few times for the bosses and rarely to the workers.

This "parabole" was originally taught by  one of my teachers in my BA in Industrial Engineering in the National University of Colombia, and hope can be useful to you. 

 1. Image taken from http://www.edupics.com/coloring-page-carriage-i18769.html