Alex Kjerulf at the Chief Happiness Officer blog has a nice post entitled "Top Five Reasons Why Most Teambuilding Events Are A Waste Of Time"

I like # 3 of the top 5...

3: People learn less when they’re competing

Studies show that we learn less when we compete and more when we cooperate. Here’s an example from education:

In a comprehensive review of 245 classroom studies that found a significant achievement difference between cooperative and competitive environments, David Johnson and Roger Johnson of the University of Minnesota reported that 87 percent of the time the advantage went to the cooperative approach.

In visiting classrooms where cooperative learning is used, I like to ask students to describe the experience in their own words. One ten-year-old boy thought a moment and replied, “It’s like you have four brains.” By contrast, a competitor’s single brain often shuts off when given no reason to learn except to triumph over his or her classmates.

- Alfie Kohn (Source)

Anyone who quotes Alfie Kohn is OK by me.