No one disputes the importance of positive feedback in the learning process. However, balancing the amount of praise vs. criticism, or informational comments vs. encouragement, is very difficult. It is in this area where coaching truly becomes an art - especially considering that every player responds differently to feedback.
A study by a team of psychologists from Columbia recently studied how event different types of praise can impact performance. The study fundamentally found that praising students for being intelligent (a percieved innate trait) vs. praising students for working hard (a controllable trait) had a huge impact on future performance. Students praised for working hard were far more likely to voluntarily take on more difficult tasks in the future than those praised for being smart. Students praised for working hard also persevered longer when faced with difficult problems. Finally, these students even tested better on subsequent tests. For a good summary of the original study and some subsequent research, you can read this article at New York Magazine.
The use of praise by John Wooden, (legendary UCLA basketball coach and winner of 10 NCAA basketball national championships), and Pat Summitt, (legendary Tennesse women's basketball coach and winner of 8 NCAA basketball national championships), was analyzed in a different research studies. A 2004 comparison of the two coaches (based on analysis of 15 practices over 30 hours run by Wooden, and 6 practices over 18 hours run by Summitt) found the following breakdown of coaching commentary:
While every coach has a different philosophy, it is helpful to see how some of the best manage their commentary, and to see what science in other fields has found. This commitment to ongoing learning by coaches is central to the FC Wisconsin Eclipse developmental philosophy.