What if your professor suffers from decision fatigue? What if you do?   Nice review by John Tierney of psychology studies on decision-making and self-control.  “Decision fatigue is the newest discovery involving a phenomenon called ego depletion, a term coined by [FSU psychology professor] Roy F. Baumeister in homage to a Freudian hypothesis. Freud speculated that the self, or ego, depended on mental activities involving the transfer of energy.  … Freud’s energy model of the self was generally ignored until the end of the century, when Baumeister began studying mental discipline in a series of experiments, first at Case Western and then at Florida State University. These experiments demonstrated that there is a finite store of mental energy for exerting self-control. … Willpower turned out to be more than a folk concept or a metaphor. It really was a form of mental energy that could be exhausted.”  More here.