The connection between self-control and glucose is not unique to humans.
A bunch of trained dogs were divided into two groups. One group was instructed to sit and stay for 10 minutes. Dogs in the other group could run around and do whatever they wanted.
Then all the dogs were given a toy containing a piece of sausage that was hard to extract. The dogs that had to stay sitting for 10 minutes gave up trying to extract the sausage in less than a minute, while the other dogs kept at much longer.
Then the experiment was run again, but this time, after having to sit for 10 minutes the dogs were given drinks.
Those that received a sugary drink kept trying to extract the sausage for as long as the dogs in the control group. But those that received a drink with an artificial sweetener, gave up again in less than a minute.
So if you want a dog with strong self-control make sure you put sugar in its lemonade.
- Willpower, 2011 book by Roy Baumeister & John Tierney, page 49
- "Self-Control Without a 'Self'?: Common Slef-control Processes in Humans and Dogs", 2010 article by H.C. Miller, K.F. Pattison, C.N. DeWall, r. Rayburn-Reeves, & T.R. Zentall, in Psychological Science 21 (2010): 534-8