The New York Times has an absolutely wonderful article about decision making fatigue. Decision Fatigue
It’s a long article, but worth the effort to plow through. Among other gems, apparently dogs make better choices when their brain glucose levels are boosted: from page 5 of the article: “After obeying sit and stay commands for 10 minutes, the dogs performed worse on self-control tests and were also more likely to make the dangerous decision to challenge another dog’s turf. But a dose of glucose restored their willpower.” This explains why I get the most bang for my training effort when I train the puppy immediately after breakfast!