Sitting up straight might boost your confidence in your own thoughts, according to a recent study. Your mother may have told you to sit up straight so that you presented a better appearance to others, but your posture could also be sending a message to yourself.
When volunteers were asked to write down their own positive and negative qualities with respect to a professional job and then asked to rate themselves as future professionals, their judgements on the two tasks were much more likely to coincide when they were sitting up straight with their chests out than when they were slouched down in their seats. This is interpreted as indicating that they gave more credence to their own thoughts when they were sitting up straight. I wonder how this would play out in something like cognitive-behavioral therapy, where you consciously try to change your own thoughts. Would it help to sit up straight in a confident posture when you are trying to reshape your mental landscape? On the other hand, I suppose you might want to avoid sitting confidently upright if you’re down on yourself.
You can read more in this article at Science Daily or in the paper itself: Body posture effects on self-evaluation: A self-validation approach, by Pablo Briñol, Richard E. Petty, Benjamin Wagner. European Journal of Social Psychology, October 2009, p. 1053-1064. (Link goes to the abstract.)