Evidently, when you are thinking about a problem, you use up glucose.
This can be seen by monitoring blood glucose as people work on math problems and the like.
Roy Baumeister conducted an experiment where the subjects solved math problems. Just before solving some of the problems, half of the subjects were given lemonade with sugar in it, and the other half were given lemonade with artificial sweetener in it. The ones who were given the sugared drink did better.
Here is something even more amazing.
In Israel, there are these people who evaluate applications for parole. Evidently, the odds of getting paroled are only 35 percent. That is, the default is to reject the application.
Well, these people just evaluate applications all day long, taking on average 6 minutes per application. Each application is time-stamped after they've been evaluated.
During work, the evaluators have a break for lunch and one for an afternoon snack. Lo and behold, the rate of approval is 65 percent, as opposed to the average of 35 percent, just after they've had something to eat—and drops to just 10 percent right before their breaks start.
So, the moral of the story—eat before you have a test.
Have you noticed a difference problem-solving or concentrating after eating compared to before eating?
- Matthew Gailliot & Roy Baumeister, "The Physiology of Willpower: Linking Blood Glucose to Self-Control"
- Shal Danziger, Jonathan Levav & Liora Avnalm-Pesso, "Extraneous factors in judicial decisions"