A recent series of studies have found that saying “thank you” can have a very positive and measurable impact. Bob Sutton summarizes it:

… a simple expression of thanks by someone in authority led people to be more likely to volunteer to do extra work. Their research shows that this happens because the simple act of being thanked makes be feel more valued — and in some of these studies — it also increased peoples’ feelings of self-efficacy (essentially, the perception that they were making a bigger impact on the world around them).

In the classroom, I say “thank you” when an individual student does something that I have specifically asked him/her to do — even if it’s something they should be doing anyway. I will also say “thank you” if a student has specifically helped me in some way. There is no question in my mind that not only is it the right thing to do, but it gets the kind of positive results found in the study.

When the class as a whole does something that I ask them to do, I will often say that I “appreciate” their cooperation, but won’t say “thank you.” When I see individual students doing good work — either academically or if they might have been courteous to someone — I offer praise for their effort, but don’t say “thank you.” When I see the class as a whole doing something exceptionally well — academically or behavior-wise — I generally will tell them that, again, I “appreciate” what they are doing, but I won’t say “thank you.”

I don’t know exactly how to explain how these last three situations are not “deserving” of a “thank you” and the first two situation are and, in fact, never really thought before how or why I handled them differently. Can anybody help me explain the difference? And do you have your own “rules” or habits about saying “thank you” in the classroom?